BACE INHIBITORS
The present invention relates to novel BACE inhibitors, to pharmaceutical
compositions comprising the compounds, to methods of using the compounds to treat
physiological disorders, and to intermediates and processes useful in the synthesis of the
compounds.
The present invention is in the field of treatment of Alzheimer's disease and other
diseases and disorders involving amyloid (Abeta) peptide, a neurotoxic and highly
aggregatory peptide segment of the amyloid precursor protein (APP). Alzheimer's
disease is a devastating neurodegenerative disorder that affects millions of patients
worldwide. In view of the currently approved agents on the market which afford only
transient, symptomatic benefits to the patient, there is a significant unmet need in the
treatment of Alzheimer's disease.
Alzheimer's disease is characterized by the generation, aggregation, and
deposition of Abeta in the brain. Complete or partial inhibition of -secretase (-site
amyloid precursor protein-cleaving enzyme; BACE) has been shown to have a significant
effect on plaque-related and plaque-dependent pathologies in mouse models suggesting
that even small reductions in Abeta peptide levels might result in a long-term significant
reduction in plaque burden and synaptic deficits, thus providing significant therapeutic
benefits, particularly in the treatment of Alzheimer's disease.
US 2012/0202804 discloses fused aminodihydro-oxazine derivatives which
possess BACE inhibitory activity and are further disclosed as useful therapeutic agents
for a neurodegenerative disease caused by Abeta peptide, such as Alzheimer's type
dementia. US 8,158,620 discloses fused aminodihydrothiazine derivatives which possess
BACE inhibitory activity and are further disclosed as useful therapeutic agents for a
neurodegenerative disease caused by Abeta peptide, such as Alzheimer's type dementia.
US 2012/0245155 discloses fused heterocyclic compounds which also possess BACE
inhibitory activity and are further disclosed as being useful for treating Alzheimer's
disease.
BACE inhibitors with central nervous system (CNS) penetration are desired to
provide treatments for Abeta peptide-mediated disorders, such as Alzheimer's disease.
The present invention provides certain novel compounds that are inhibitors of BACE. In
addition, the present invention provides certain novel compounds which penetrate the
CNS. The present invention also provides certain novel compounds which have the
potential for an improved side-effect profile.
Accordingly, the present invention provides a compound of Formula I :
Formula I
wherein A is:
R is H, F, CI, CN, OCH2CF3, or OCH2CF2CHF2;
R2 is H, CH3, F, or CI;
R3 is H, F, or CI; and
R4 is H, F, CI, CH3, OCH3, CF3, OCH2CF3,
Of , or Oor
a pharmaceutically acceptable salt thereof.
The present invention further provides a compound of Formula II:
2 Formula II
wherein A is:
R1 is H, F, CI, CN, or OCH2CF3;
R2 is H, F, CI, or CH3; and
R3 is H, OCH3, or OCH2CF3;
or a pharmaceutically acceptable salt thereof.
The present invention further provides a compound of Formula III:
Formula H
wherein A is:
Z is O or S;
R1 is H, F, CI, CN, OCH3, OCH2CH2OCH3,
R2 is H, F, CI, or CH3;
R3 is H, F, CI, CH3, CF3, C1-C3 alkoxy, OCH2CH2OCH3,
R4 is H, F, CI, or OCH3;
or a pharmaceutically acceptable salt thereof.
The present invention also provides a method of treating Alzheimer's disease in a
patient, comprising administering to a patient in need of such treatment an effective
amount of a compound of Formulas I, II, or III, or a pharmaceutically acceptable salt
thereof.
The present invention further provides a method of preventing the progression of
mild cognitive impairment to Alzheimer's disease in a patient, comprising administering
to a patient in need of such treatment an effective amount of a compound of Formulas I,
II, or III, or a pharmaceutically acceptable salt thereof. The present invention also
provides a method of inhibiting BACE in a patient, comprising administering to a patient
in need of such treatment an effective amount of a compound of Formulas I, II, or III, or a
pharmaceutically acceptable salt thereof. The present invention also provides a method
for inhibiting BACE-mediated cleavage of amyloid precursor protein, comprising
administering to a patient in need of such treatment an effective amount of a compound of
Formulas I, II, or III, or a pharmaceutically acceptable salt thereof. The invention further
provides a method for the inhibition of production of Abeta peptide, comprising
administering to a patient in need of such treatment an effective amount of a compound of
Formulas I, II, or III, or a pharmaceutically acceptable salt thereof.
Furthermore, this invention provides a compound of Formulas I, II, or III, or a
pharmaceutically acceptable salt thereof for use in therapy, in particular for the treatment
of Alzheimer' s disease or for the prevention of the progression of mild cognitive
impairment to Alzheimer's disease. Even furthermore, this invention provides the use of
a compound of Formulas I, II, or III, or a pharmaceutically acceptable salt thereof, for the
manufacture of a medicament for the treatment of Alzheimer's disease.
The invention further provides a pharmaceutical composition, comprising a
compound of Formulas I, II, or III, or a pharmaceutically acceptable salt thereof, with one
or more pharmaceutically acceptable carriers, diluents, or excipients. In a particular
embodiment, the composition further comprises one or more other therapeutic agents.
This invention also encompasses novel intermediates and processes for the synthesis of
the compounds of Formulas I, II, or III.
Mild cognitive impairment has been defined as a potential prodromal phase of
dementia associated with Alzheimer's disease based on clinical presentation and on
progression of patients exhibiting mild cognitive impairment to Alzheimer's dementia
over time. (Morris, et ah, Arch. Neurol, 58, 397-405 (2001); Petersen, et a , Arch.
Neurol, 56, 303-308 (1999)). The term "prevention of the progression of mild cognitive
impairment to Alzheimer's disease" includes slowing, arresting, or reversing the
progression of mild cognitive impairment to Alzheimer's disease in a patient.
As used herein, the terms "treating" or "to treat" includes restraining, slowing,
stopping, or reversing the progression or severity of an existing symptom or disorder.
As used herein, the term "patient" refers to a human.
As used herein, the term "C1-C3 alkoxy" refers to methoxy, ethoxy, n-propoxy,
and isopropoxy groups.
The term "inhibition of production of Abeta peptide" is taken to mean decreasing
of in vivo levels of Abeta peptide in a patient.
As used herein, the term "effective amount" refers to the amount or dose of
compound of the invention, or a pharmaceutically acceptable salt thereof which, upon
single or multiple dose administration to the patient, provides the desired effect in the
patient under diagnosis or treatment.
An effective amount can be readily determined by the attending diagnostician, as
one skilled in the art, by the use of known techniques and by observing results obtained
under analogous circumstances. In determining the effective amount for a patient, a
number of factors are considered by the attending diagnostician, including, but not limited
to: the species of patient; its size, age, and general health; the specific disease or disorder
involved; the degree of or involvement or the severity of the disease or disorder; the
response of the individual patient; the particular compound administered; the mode of
administration; the bioavailability characteristics of the preparation administered; the
dose regimen selected; the use of concomitant medication; and other relevant
circumstances.
The compounds of the present invention are generally effective over a wide
dosage range. For example, dosages per day normally fall within the range of about 0.01
to about 20 mg/kg of body weight. In some instances dosage levels below the lower limit
of the aforesaid range may be more than adequate, while in other cases still larger doses
may be employed with acceptable side effects, and therefore the above dosage range is
not intended to limit the scope of the invention in any way.
The compounds of the present invention are preferably formulated as
pharmaceutical compositions administered by any route which makes the compound
bioavailable, including oral and parenteral routes. Most preferably, such compositions
are for oral administration. Such pharmaceutical compositions and processes for
preparing same are well known in the art. (See, e.g., Remington: The Science and
Practice of Pharmacy (D.B. Troy, Editor, 21st Edition, Lippincott, Williams & Wilkins,
2006).
The compounds of Formulas I, II, and III, or pharmaceutically acceptable salts
thereof are particularly useful in the treatment methods of the invention, but certain
groups, substituents, and configurations are preferred for compounds of Formulas I, II,
and III. The following paragraphs describe such preferred groups, substituents, and
configurations. It will be understood that these preferences are applicable both to the
treatment methods and to the new compounds of the invention.
Thus, for compounds of Formula I, or pharmaceutically acceptable salts thereof:
It is preferred that A is:
It is further preferred that A is:
It is especially preferred that A is:
It is preferred that R1 is CN or F, with CN being especially preferred.
It is preferred that R2 is H.
It is especially preferred that when R1 is CN or F, R2 is H.
It is further especially preferred that when R1 is CN, R2 is H.
In addition, it is preferred that R3 is CI.
It is also preferred that R4 is OCH3.
One of ordinary skill in the art will appreciate that compounds of Formula I
comprised of a core that contains two chiral centers as shown below in Scheme A:
heme A
Although the present invention contemplates all individual enantiomers and diasteromers,
as well as mixtures of the enantiomers of said compounds, including racemates, the
compounds with the absolute configuration at the carbon atoms labeled 1 and 2 as
illustrated in Scheme A are preferred compounds of the invention.
For compounds of Formula II, or pharmaceutically acceptable salts thereof:
It is preferred that R is CN.
It is preferred that R2 is H.
It preferred that R3 is OCH3.
It further preferred that A is:
It especially preferred that when R1 is CN, R2
It is further especially preferred that A is:
It is further especially preferred that A is:
One of ordinary skill in the art will appreciate that compounds of Formula II
comprised of a core that contains two chiral centers as shown below in Scheme B:
Scheme B
Although the present invention contemplates all individual enantiomers and
diasteromers, as well as mixtures of the enantiomers of said compounds, including
racemates, the compounds with the absolute configuration at the carbon atoms labeled 1
and 2 as illustrated in Scheme B are preferred compounds of the invention.
and pharmaceutically acceptable salts thereof.
For compounds of Formula III, or pharmaceutically acceptable salts thereof:
It is preferred that A is:
It is further preferred that A is:
It is especially preferred that A is:
It is most especially preferred that A is:
It is preferred that R1 is CN.
It is preferred that R2 is H.
It is further preferred that when R1 is CN,
It is preferred that R3 is OCH3, CH2CF3
It is especially preferred that R3 is OCH3.
It is preferred that compounds of Formula III are in the (cis)-configuration about
the fused rings as shown below:
H
In addition, one of ordinary skill in the art will appreciate that compounds of
Formula III are comprised of a core that contains two chiral centers as shown below in
Scheme C:
Scheme C
Although the present invention contemplates all individual enantiomers and
diasteromers, as well as mixtures of the enantiomers of said compounds, including
racemates, the compounds with the absolute configuration at the carbon atoms labeled 1
and 2 as illustrated in Scheme C are preferred compounds of the invention.
Preferred compounds are:
1
F3C
and pharmaceutically acceptable salts thereof.
Most preferred compounds are:
and pharmaceutically acceptable salts thereof.
Especially preferred is:
and pharmaceutically acceptable salts thereof.
More particularly, the following compounds are preferred:
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]-5-cyano-pyridine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]-5-methoxy-pyrazine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl] -5-[(1-fluorocyclopropyl)methoxy]pyrazine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]-5-(2,2,2-trifluoroethoxy)pyrazine-2-carboxamide;
N-[3-[(4aR,7aS)-2-aniino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7ayl]-
4-fluoro-phenyl]-5-methoxy-pyrazine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d] [1,3]thiazin-7ayl]-
4-fluoro-phenyl]-5-cyano-pyridine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7ayl]-
4-fluoro-phenyl]-5-[(2,2-difluorocyclopropyl)methoxy]pyrazine-2-carboxamide; and
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7ayl]-
4-fluoro-phenyl]-5-(cyclopropylmethoxy)pyrazine-2-carboxamide;
and pharmaceutically acceptable salts thereof.
More preferred compounds are
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]-5-cyano-pyridine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]-5-methoxy-pyrazine-2-carboxamide;
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7ayl]-
4-fluoro-phenyl]-5-methoxy-pyrazine-2-carboxamide; and
N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7ayl]-
4-fluoro-phenyl]-5-cyano-pyridine-2-carboxamide;
and pharmaceutically acceptable salts thereof.
An especially preferred compound is N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-
dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-fluoro-phenyl]-5-cyano-pyridine-2-
carboxamide, and pharmaceutically acceptable salts thereof.
One of ordinary skill in the art will appreciate that compounds of the invention
can exist in tautomeric forms, as depicted in Scheme D. When any reference in this
application to one of the specific tautomers of the compounds of the invention is given, it
is understood to encompass both tautomeric forms and all mixtures thereof.
Scheme D
Certain stereochemical centers have been left unspecified and certain substituents
have been eliminated in the following schemes for the sake of clarity and are not intended
to limit the teaching of the schemes in any way. Furthermore, individual isomers,
enantiomers, and diastereomers may be separated or resolved by one of ordinary skill in
the art at any convenient point in the synthesis of compounds of Formulas I, II, and III, by
methods such as selective crystallization techniques or chiral chromatography (See for
example, J. Jacques, et al., "Enantiomers, Racemates, and Resolutions", John Wiley and
Sons, Inc., 1981, and E.L. Eliel and S.H. Wilen," Stereochemistry of Organic
Compounds", Wiley-Interscience, 1994). The designations "isomer 1" and "isomer 2"
refer to the compounds that elute from chiral chromatography first and second,
respectively, and if chiral chromatography is initiated early in the synthesis, the same
designation is applied to subsequent intermediates and examples.
Additionally, certain intermediates described in the following schemes may
contain one or more nitrogen protecting groups. The variable protecting group may be
the same or different in each occurrence depending on the particular reaction conditions
and the particular transformations to be performed. The protection and deprotection
conditions are well known to the skilled artisan and are described in the literature (See for
example "Greene 's Protective Groups in Organic Synthesis", Fourth Edition, by Peter
G.M. Wuts and Theodora W. Greene, John Wiley and Sons, Inc. 2007).
Certain abbreviations are defined as follows: "APP" refers to amyloid precursor
protein; "CSF" refers to cerebrospinal fluid; "DCC" refers to 1,3-
dicyclohexylcarbodiimide; "DIC" refers to diisopropylcarbodiimide; "DIPEA" refers to
diisopropylethylamine or N-ethyl-N-isopropyl-propan-2 -amine; "ACN" refers to
acetonitrile; "DMAP" refers to dimethylaminopyridine; "DMEM" refers to Dulbecco's
Modified Eagle's Medium; "DMF" refers to dimethylformamide; "DMSO" refers to
dimethyl sulfoxide; "EDO" refers to l-(3-dimethylaminopropyl)-3-ethylcarbodiimide
hydrochloride; "ee" refers to enantiomeric excess; "Ex" refers to example; "F12" refers to
Ham's F12 medium; "FBS" refers to Fetal Bovine Serum; "FRET" refers to fluorescence
resonance energy transfer; "HATU" refers to (dimethylamino)-N,N-dimethyl(3H-
[l,2,3]triazolo[4,5-ft]pyridin-3-yloxy)methaniminium hexafluorophosphate; "" refers
to human embryonic kidney; "HOAc" refers to acetic acid; "HOAt" refers to 1-hydroxy-
7-azobenzotriazole; "HOBt" refers to 1-hydroxyIbenzotriazole hydrate; "HBTU" refers to
refers to 2-(l H-benzotriazole-l-yl)-l,l,3,3-tetramethyluronium hexafluorophosphate;
"HPLC refers to high-performance liquid chromatography; "IC50" refers to the
concentration of an agent that produces 50% of the maximal inhibitory response possible
for that agent; "min" refers to minute or minutes; "MeOH" refers to methanol or methyl
alcohol; "MTBE" refers to methyl rt-butyl ether; "PDAPP" refers to platelet derived
amyloid precursor protein; "PG" refers to protecting group; "Prep" refers to preparation;
"PyBOP" refers to benzotriazol-l-yloxytripyrrolidino-phosphonium
hexafluorophosphate; "PyBrop" refers to bromo-tris-pyrrolidino phosphoniumhexafluoro
phosphate; "RFU" refers to relative fluorescence unit; "SCX" refers to strong cation
exchange; "SFC" refers to supercritical fluid chromatography; and "THF" refers to
tetrahydrofuran.
The compounds of the present invention, or salts thereof, may be prepared by a
variety of procedures known in the art, some of which are illustrated in the Schemes,
Preparations, and Examples below. The specific synthetic steps for each of the routes
described may be combined in different ways, or in conjunction with steps from different
schemes, to prepare compounds of Formulas I, II, and III, or salts thereof. The products
of each step in the schemes below can be recovered by conventional methods well known
in the art, including extraction, evaporation, precipitation, chromatography, filtration,
trituration, and crystallization. In the schemes below, all substituents unless otherwise
indicated, are as previously defined. The reagents and starting materials are readily
available to one of ordinary skill in the art.
Scheme 1
Step C
St
In Scheme 1, step A, bromoacetyl bromide is treated with N,0-
dimethylhydroxylamide hydrochloride under conditions well known in the art, using an
inorganic base, such as potassium carbonate or an organic base, such as
diisopropylethylamine, to provide the Weinreb amide.
In Scheme 1, step B, the Weinreb amide is treated with allyl alcohol and an
inorganic base, such as potassium carbonate, under conditions well known in the art to
provide the allyl ether. For example, the Weinreb amide is added to about 6-7
equivalents of allyl alcohol and about 2 equivalents of a suitable base, such as potassium
carbonate over about 3 hours at about 30 °C. The reaction mixture is allowed to stir for
about 2 hours at about 30 °C, and a suitable organic solvent is added, such as toluene.
The mixture is then cooled to about 0 °C and filtered. The filter cake is washed with cold
(about 0 °C) toluene, and the organic filtrates combined and rinsed with aqueous
potassium bisulfate. The organic phase is then concentrated with additional toluene
added to remove water and excess allyl alcohol. The organic is again washed with water
and then concentrated to remove most of the toluene. The organic residue is finally
distilled to provide the allyl ether.
In Scheme 1, step C, 4-bromo-l-fluoro-2-iodobenzene is reacted with the allyl
ether using a Grignard reagent such as isopropylmagnesium chloride to provide the
substituted allyloxy ethanone. For example, about 1 equivalent of a suitable Grignard
reagent, such as isopropylmagnesium chloride in THF, is add to about 0.95 equivalents of
4-bromo-l-fluoro-2-iodobenzene in a suitable organic solvent, such as THF, at about 0 °C
with stirring. After about 60 minutes at about 0 °C, about 1 equivalent of the allyl ether
in a suitable organic solvent, such as THF is added over about 60 minutes. The reaction
is then quenched with excess aqueous ammonium chloride at about 0 °C. A suitable
organic solvent, such as heptanes, is added to the quenched reaction mixture with stirring
as the mixture is warmed to room temperature. The layers are then separated and the
organic layer is washed with water, and concentrated with addition of heptanes to remove
water and THF, providing the allyloxy ethanone.
In Scheme 1, step D, the bicyclic isoxazole can be formed from the allyloxy
ethanone by several methods, such as using a 2-step procedure where an oxime is formed
in situ using hydroxylamine, and then cyclized to the bicyclic isoxazolidine (PG = H).
Alternatively, a substituted hydroxylamine, such as 1-phenylpropyl hydroxylamine ptoluenesulfonic
acid salt is treated with potassium bicarbonate followed by heating with
titanium tetraisopropoxide to give a nitrone intermediate in situ that cyclizes to the
nitrogen protected bicyclic isoxazole. For example, a suitable 1-phenylpropyl
hydroxylamine p-toluenesulfonic acid salt, such as (R)-N-(lphenylpropyl)
hydroxylamine />-toluenesulfonic acid salt (see Patel, I.; Smith, N.A.; Tyler,
S. N. G. Organic Process Research &Development 2009, 13, 49-53) is treated with
about 2.75 equivalents of potassium bicarbonate, water, and a suitable organic solvent,
such as MTBE. The layers are separated and the organic layer is washed with aqueous
sodium chloride. A suitable organic solvent is added to the organic layer, and most of the
MTBE and water are removed by distillation at about 50 °C. About 1 equivalent of about
a 20-25% weight% solution of the allyloxy ethanone in heptanes is added to the 1-
phenylpropyl hydroxylamine in heptanes at about 50 °C. About 1.5 equivalents of
titanium tetraisopropoxide is then added and the mixture is heated at about 55-60 °C for
about 10 hours (Titanium (IV) ethoxide can also be used). The nitrogen protected
bicyclic isoxazole is then isolated under conditions well known in the art, such as
concentration, cooling, and collection by filtration.
In Scheme 1, step E, the bicyclic isoxazole is converted to the nitrogen protected
aniline bicyclic isoxazolidine. For example, about 1 equivalent of the bicyclic
isoxazolidine is combined with about 4 equivalents of acetamide, about 0.2 equivalents
of a suitable catalyst, such as copper (I) iodide, about 0.7 equivalents of potassium iodide,
about 2 equivalents of tripotassium phosphate, and about 0.8 equivalents of N,Ndimethylethylenediamine
in a suitable organic solvent, such as DMF. The reaction
mixture is then heated at about 110 °C for about 4 hours. The nitrogen protected aniline
bicyclic isoxazolidine is isolated using techniques and conditions well known in the art.
For example, the reaction mixture is cooled to about 30 °C and portioned between a
suitable organic solvent, such as isopropyl acetate and aqueous ammonium chloride. The
layers are separated and the aqueous layer is further extracted with isopropyl acetate. The
organic extracts are combined, washed with aqueous ammonium chloride, and the organic
layer is mixed with a suitable organic solvent, such as xylenes. The organic mixture is
then distilled to remove most of the isopropyl acetate and residual DMF. The organic
mixture is then cooled to about 0 °C and the resulting solid nitrogen protected aniline
bicyclic isoxazolidine is collected by filtration.
In Scheme 1, step F, the nitrogen protected aniline bicyclic isoxazolidine ring can
be opened and the isoxazolidine nitrogen also deprotected under standard conditions well
known in the art to provide the amino-hydroxymethyl-tetrahydrofuran. For example,
about 1 equivalent of the nitrogen protected aniline bicyclic isoxazolidine ring is
combined with about 0.2 equivalents zinc chloride and about a 20% weight loading of
water wet sulfided 5% palladium on carbon catalyst slurried in a mixture of
propanol/water and about 0.9 equivalents HC1. The mixture is heated at about 50 °C
under hydrogen at about 300-400 kPa for about 16 hours. The catalyst is then removed
by filtration and the filter cake is rinsed with propanol. Most of the water is then removed
from the filtrate by azeotropic distillation with additional propanol addition. Additional
HC1 is added (about 0.1 equivalent) in water and the solid collected to provide the aminohydroxymethyl-
tetrahydrofuran. Alternatively, powdered zinc in HOAc or Raney Ni
under hydrogenation conditions can be used to open the isoxazolidine ring.
In Scheme 1, step G, the amino-hydroxymethyl-tetrahydrofuran is first protected
with a suitable nitrogen protecting group. The hydroxyl group is subsequently oxidized
under conditions well known in the art to provide the aldehyde. For example, the aminohydroxymethyl-
tetrahydrofuran is combined with about 2-3 equivalents of a suitable
organic base, such as triethylamine and about 1.2-1.4 equivalents of a suitable nitrogen
protecting group reagent, such as di-t r t-butyl dicarbonate in a suitable organic solvent,
such as THF. The reaction is stirred at about 50 °C for about 15-18 hours and the
resulting nitrogen protected intermediate is isolated and purified using techniques well
known in the art. For example, the reaction is cooled to room temperature and
concentrated. The residue is partitioned between 10% citric acid and ethyl acetate,
extracted with ethyl acetate, dried, and concentrated to provide the nitrogen protected
intermediate. Alternatively, the reaction is cooled to room temperature, filtered, the
solids washed with ethyl acetate, and the filtrate concentrated under reduced pressure.
The residue is then purified by chromatography on silica gel, eluting with a suitable
eluent, such as methanol :dichloromethane gradient 0 :10 to 1:10 to provide the nitrogen
protected intermediate of step G, substep 1. The nitrogen protected intermediate is then
oxidized to the aldehyde under conditions well known to one of ordinary skill in the art in
step G, substep 2. For example, the nitrogen protected intermediate prepared directly
above, dissolved in a suitable organic solvent, such as dichloromethane, is added to a
stirring mixture of a suitable oxidizing agent, such as about 1.7 equivalents of pyridinium
chlorochromate, 4A molecular sieves, and about 2.3 equivalents of ammonium acetate in
dichloromethane. The suspension is stirred at room temperature for about 35 minutes to
about 2 hours. The resulting aldehyde compound of step G, substep 2 is then isolated and
purified using techniques well known in the art. For example, the reaction mixture is
partially concentrated under reduced pressure, a suitable organic solvent, such as ethyl
acetate is added, and the mixture is filtered through silica gel. The silica gel is further
rinsed with ethyl acetate, the filtrates are combined, and then concentrated under reduced
pressure to provide the aldehyde. Alternatively, to the nitrogen protected intermediate
prepared directly above, dissolved in a suitable organic solvent, such as DMSO is added
2-iodoxybenzoic acid (IBX) and the mixture is stirred about 18 hours. The mixture is
added to a sodium carbonate aqueous solution, MTBE is added and the mixture is stirred
at room temperature for about 15 minutes, filtered through diatomaceous earth and the
organic layer is collected, and concentrated to give the aldehyde compound of step G,
substep 2.
In Scheme 1, step H, substep 1, the aldehyde of step G is fluorinated using 1-
chloromethyl-4-fluoro- 1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (also
referred to as Selectfluor™) to provide the fluorinated compound, and the aldehyde is
then reduced in substep 2 to give the fluorinated primary alcohol. For example, the
aldehyde is dissolved in a suitable organic solvent, such as THF and treated with about
1.08 equivalents of a suitable secondary cyclic amine, such as pyrrolidine or D-(+)-
proline. The solution is stirred at room temperature for about 5 to 10 minutes and treated
with about 1.15 equivalents of Selectfluor™, and the reaction is stirred for about 2 to 3
hours. The reaction is then quenched with saturated aqueous sodium bicarbonate and
extracted with suitable organic solvents, such as ethyl acetate and dichloromethane. The
organic extracts are combined, dried over a suitable drying agent, such as anhydrous
magnesium sulfate or sodium sulfate, filtered, and concentrated under reduced pressure.
Alternatively, about 1.1 equivalents of D-(+)-proline is added to a solution of the
aldehyde in 2,2,2-trifuloro-ethanol that is treated with potassium carbonate and 3A
molecular sieves and filtered prior to use. Other solvents, such as methanol, ethanol,
THF, and dichloromethane may also be used, which may produce different
diastereoselectivities. 3A Molecular sieves (500 mg) are added and the reaction mixture
is stirred at room temperature for about 4 hours. About 1.3 equivalents of Selectfluor™ is
added to the mixture and it is stirred for about 36 hours. The mixture is concentrated and
purified using techniques well known in the art to give the unreduced fluorinated product
of step H, substep 1
In step H, substep 2, the residue is dissolved in a suitable organic solvent, such as
methanol or ethanol, treated with 1.07-1.4 equivalents of a suitable reducing agent, such
as sodium borohydride or sodium tetrahydroborate, and the reaction is then stirred at
room temperature for about 30 minutes to 2 hours. The reaction is then quenched with
saturated aqueous sodium bicarbonate or evaporated to a residue, and extracted with
suitable organic solvents, such as ethyl acetate and dichloromethane. The organic
extracts are combined, dried over a suitable drying agent, such as anhydrous magnesium
sulfate or sodium sulfate, filtered, and concentrated under reduced pressure to provide the
crude fluorinated primary alcohol. This crude material is then purified using techniques
well known in the art, such as flash chromatography on silica gel with a suitable eluent,
such as a methanol :dichloromethane gradient of 0:10 to 1:10 or ethyl acetate/hexane (1:1)
providing the purified fluorinated primary alcohol of step H. Other methods known to
one of ordinary skill in the art to accomplish a direct fluorination utilize Selectfluor™, a
copper(I) bisimine complex, and anionic phase-transfer catalyst and Nhydroxyphthalimide
or N,N-dihydroxypyromellitimide and Selectfluor™. Fluorinating
reagents, in addition to Selectfluor™, which may be used, include the following: Nfluoropyridinium
trifluoromethanesulfonate and N-fluorobenzenesulfonimide, which may
produce different diastereoselectivities.
Scheme 2
Formula I or Formula Ilia (Z is S)
In Scheme 2, step I, the fluorinated primary alcohol of step H is deprotected under
standard conditions allowing the deprotected amine to then be converted to the thiourea
utilizing conditions well known in the art. For example, in substep 1, deprotection, the
fluorinated primary alcohol is dissolved in a suitable organic solvent, such as
dichloromethane and treated with an excess of a suitable acid such as about 15
equivalents of trifluoroacetic acid. The reaction is stirred at room temperature for about 2
to 3 hours. The reaction is then concentrated under reduced pressure, azeotroping with
toluene. In substep 2, thiourea formation, the residue is then dissolved in a suitable
organic solvent, such as THF and treated with about 1.1 equivalents of a suitable organic
amine, such as triethylamine, and about 1.06 equivalents of benzoyl isothiocyanate. The
reaction is then stirred at room temperature for about 16 to 18 hours and then quenched
with aqueous saturated sodium bicarbonate. The quenched reaction is then extracted with
suitable organic solvents, such as ethyl acetate and dichloromethane. The organic
extracts are combined, dried over a suitable drying agent, such as anhydrous magnesium
sulfate, filtered, and concentrated under reduced pressure to provide the crude thiourea
product of step I. This crude material is then purified using techniques well known in the
art, such as flash chromatography on silica gel with a suitable eluent, such as a
methanol: dichloromethane gradient of 0 :10 to 1:10 providing the purified thiourea.
In Scheme 2, step J, cyclization, the thiourea of step I is cyclized to the protected
bicyclic aminothiazine under standard conditions. For example, the thiourea is dissolved
in a suitable organic solvent, such as dichloromethane and treated with about 1.44
equivalents of l-chloro-N,N,2-trimethylpropenylamine. The reaction is then stirred at
room temperature for about 3 to 4 hours, and the reaction is quenched with saturated
aqueous sodium bicarbonate. The quenched reaction is then extracted with a suitable
organic solvent, such as dichloromethane. The organic extracts are combined, dried over
a suitable drying agent, such as anhydrous magnesium sulfate, filtered, and concentrated
under reduced pressure to provide the crude bicyclic aminothiazine product of step J. The
crude material is then purified using techniques well known in the art, such as flash
chromatography on silica gel with a suitable eluent, such as an ethyl acetate:hexane
gradient of 0 :1 to 1:0 providing the purified bicyclic aminothiazine .
In Scheme 2, step K, the bicyclic aminothiazine product of step J is deprotected
in substep 1 under conditions well known in the art, and then in substep 2, an amidation is
carried out under conditions well known in the art with a suitable aryl acyl chloride (A-
(C=0)-C1), wherein "A" is as defined herein, to provide the compounds of Formula I or
Formula Ilia, (Z is S). For example, the bicyclic aminothiazine is combined with about
5.6 equivalents of O-methylhydroxylamine hydrochloride and about 5.9 equivalents of
pyridine in a suitable organic solvent, such as ethanol, and heated at about 50 °C for about
16 hours. Then about 25 equivalents of a suitable acid, such as concentrated hydrochloric
acid is added and the reaction is heated at about 50 °C for an additional 24 hours. The
reaction is then cooled and concentrated under reduced pressure to provide the crude
deprotected diamino compound which is then purified by techniques well known in the
art, such as flash chromatography on silica gel eluting with a suitable eluent, such as 7 M
ammonia in methanol/dichloromethane gradient 0 :10 to 1:10 to provide the purified
deprotected diamino compound.
Alternatively, the bicyclic aminothiazine product of step J is combined with about
9.4 equivalents of O-methylhydroxylamine hydrochloride and about 9.9 equivalents of
pyridine in a suitable organic solvent, such as ethanol, and heated at about 50 °C for about
18 hours. The reaction is then purified directly, for example, by use of an SCX column,
utilizing a suitable eluent, such as in methanol followed by 7 M ammonia in methanol.
The purified material is then dissolved in a suitable organic solvent, such as ethanol,
treated with about 16 equivalents of a suitable acid, such as concentrated hydrochloric
acid and heated at 50 °C for about 23 hours. The reaction is then cooled and concentrated
under reduced pressure to provide the crude deprotected diamino compound which can be
purified by techniques well known in the art, such as flash chromatography or an SCX
column utilizing a suitable eluent, such as methanol followed by 7 M ammonia in
methanol.
The deprotected diamino can then be amidated in step K, substep 2 under
conditions well known in the art, using for example, an aryl acyl chloride to provide
compounds of Formula I or Formula Ilia. For example, 2 equivalents of oxalyl chloride
is added to 2.2 equivalents DMF in a suitable organic solvent, such as acetonitrile, and the
reaction is stirred for about 10 minutes. About 2.05 equivalents of the appropriately
substituted aryl carboxylic acid (A-C0 2H) is added to the reaction which is allowed to stir
for about 30 to 60 minutes producing about 2 equivalents of the corresponding aryl acyl
chloride. About 1 to 2 equivalents of the freshly prepared aryl acyl chloride is added drop
wise to a solution of the deprotected diamino compound, prepared above, in ethanol:water
(about 1:1 vol) at about 50 °C. The reaction is heated at 50 °C for about 45 to 90 minutes.
The resulting compound of Formula I or Formula Ilia is then isolated and purified using
techniques and conditions well known in the art. For example, the reaction mixture is
combined with saturated aqueous sodium bicarbonate and extracted with a suitable
organic solvent, such as dichloromethane. (The reaction mixture can also be loaded on an
SCX column directly, purified, and then further purified by silica gel.) The organic layers
are combined, washed with brine, and concentrated under reduced pressure to provide the
crude material for Formula I or Formula Ilia. The crude material can then be purified, for
example, by flash chromatography on silica gel using a suitable eluent, such as 7 M
ammonia in methanol/dichloromethane gradient of 0 :10 to 1:10. The purified material
can be further purified by reverse phase flash chromatography using a high resolution
CI 8 column eluting with a suitable eluent, such as 5 to 60% gradient of acetonitrile in 10
mM ammonium bicarbonate aqueous solution with 5% methanol. The eluent containing
product is then extracted with 4:1 chloroformdsopropanol. The organic extracts are
combined, washed with brine, dried over anhydrous magnesium sulfate, filtered, and
concentrated under reduced pressure to provide the further purified compounds of
Formula I or Formula Ilia as a free base.
Alternatively one skilled in the art will recognize that there are a number of
methods and reagents for amide formation resulting from the reaction of carboxylic acids
and amines. For example, the reaction of the deprotected diamino compound with an
appropriate aryl carboxylic acid (A-C0 2H) in the presence of a coupling reagent and an
amine base, such as DIPEA or triethylamine, will provide a compound of Formula I or
Formula Ilia. Coupling reagents include carbodiimides, such as DCC, DIC, EDCI, and
aromatic coupling reagents, such as HOBt and HOAt. Additionally, uronium or
phosphonium salts of non-nucleophilic anions, such as HBTU, HATU, PyBOP, and
PyBrOP can be used in place of the more traditional coupling reagents. Additives such as
DMAP may be used to enhance the reactions and provide compounds of Formula I or
Formula Ilia.
Scheme 3
Formula II or Formula nib (Z is O)
In Scheme 3, step L, substep 1, the fluorinated primary alcohol (prepared in
Scheme 1, step H) is deprotected under standard conditions followed by neutralization,
thiourea formation and cyclization in substeps 2a and 2b to provide the protected bicyclic
aminooxazine. For example, in substep 1, the fluorinated primary alcohol is dissolved in
a suitable organic solvent, such as ethyl acetate or dichloromethane and treated with an
excess of a suitable acid such as hydrochloric acid (4 M in 1,4-dioxane) or trifluoroacetic
acid. The reaction is stirred at room temperature for about 2 hours to overnight. The
deprotected amine is then isolated with techniques well known in the art such as filtration
as a salt. Alternatively for substep 1, ethanol is added drop wise to a solution of excess
acetyl chloride in ethyl acetate at about 0 °C and stirring for about 30 minutes. The
fluorinated primary alcohol, (Scheme 1, step H) is added and the reaction is stirred
overnight at room temperature. The deprotected amine salt is then isolated with
techniques well known in the art such as filtration. Then, for the neutralization and
thiourea formation for substep 2a, the deprotected amine salt is dissolved in a suitable
organic solvent, such as acetonitrile or tetrahydrofuran and treated with about 1.1
equivalents of a suitable organic amine, such as triethylamine to neutralize the amine, and
about 1.05 equivalents of benzoyl isothiocyanate is added to form the intermediate
thiourea. The reaction is then stirred at 5 °C for about 1 hour or heated to about 70 °for 2
hours. To cyclize and form the protected bicyclic aminooxazine in substep 2b, about 1.1
equivalents of trimethylsilyl chloride and DMSO are added and stirring is continued for
about 2 hours. The reaction is quenched with potassium phosphate dibasic (20%) to
adjust the pH to 7-8 and the product is isolated using techniques well known in the art to
give the protected bicyclic aminooxazine product of step L. Alternatively, the amine salt
can be neutralized with triethylamine as described above for step L, step 2a, and treated
with benzoylcarbamate to form an N-carbamoyl benzamide intermediated that is then
cyclized with diethylaminosulfur trifluoride in an organic solvent such as
dichloromethane at about -78 °C and warmed to about room temperature over 1 hour.
The product is isolated using techniques well known in the art to give the protected
bicyclic aminooxazine product of step L.
In Scheme 3, step M, deprotection of the protected bicyclic aminooxazine is first
completed and then the aniline is deprotected under conditions well known in the art,
followed by amidation of the aniline in substep 2 with a suitable aryl acyl chloride-A,
wherein "A" is as defined herein, to provide compounds of Formula II or Formula Illb (Z
is O). For example, in step M, substep 1, the protected bicyclic aminooxazine is added to
a solution of about 1.1 equivalents of lithium hydroxide in methanol and heated to 40 °C
for about 18 hours to deprotect the amino group on the bicyclic aminooxazine. The
aniline is then deprotected under conditions well known in the art such as acidic
conditions using aqueous 1M hydrogen chloride and heating to 90 °C for about 3 hours.
The reaction is then cooled, diluted with ethyl acetate, and the aqueous layer separated
and treated with aqueous sodium hydroxide solution to adjust the pH to about 10. This
mixture is then extracted with ethyl acetate, and concentrated under reduced pressure to
provide the deprotected crude diamino compound. The deprotected crude diamino
compound is then purified by techniques well known in the art, such as flash
chromatography on silica gel eluting with a suitable eluent, such as 7 M ammonia in
methanol/dichloromethane gradient to provide the purified deprotected diamino
compound.
Then, in Scheme 3, step M, substep 2, the deprotected diamino compound is
amidated at the aniline nitrogen under conditions well known in the art, using for example
an aryl acyl chloride to provide compounds of Formula II or Formula Illb. For example,
about 1 equivalent of oxalyl chloride and a catalytic amount of DMF is added to about
1.07 equivalents of the aryl carboxylic acid (A-C0 2H) in a suitable organic solvent such
as acetonitrile and the mixture is stirred for about 10 minutes. This mixture is then added
to a 50 °C solution of the deprotected diamino compound in ethanol and water and is
stirred at about 50 °C for about 10 minutes. The resulting compound of Formula II or
Formula Illb is then isolated and purified using techniques and conditions well known in
the art. For example, the reaction mixture is combined with saturated aqueous sodium
bicarbonate and extracted with a suitable organic solvent, such as ethyl acetate. The
crude material can then be purified, for example, by flash chromatography on silica gel
using a suitable eluent, such as a gradient of 7 M ammonia in methanol/dichloromethane
to provide the compound of Formula II or Formula Illb as a free base.
Alternatively, in Scheme 3, step N, substep 1, the fluorinated primary alcohol of
Scheme 1, step H can be deprotected as described above for step L, substep 1, neutralized
and cyclized in substeps 2a and 2b without first protecting the amine, and amidated in
substep 3 under conditions well known in the art. For example, the amine can be
deprotected in substep 1 under acidic conditions well known in the art using an excess of
a suitable acid such as hydrochloric acid (4 M in 1,4-dioxane) or trifluoroacetic acid. The
deprotected amine, as an HC1 salt, is then isolated with techniques well known in the art
such as filtration. The protected aniline, hydroxyl HC1 amine is neutralized in substep 2b
by dissolving it in a suitable organic solvent such as dichloromethane and treated with
about 1.2 equivalents of an organic base such as triethylamine, stirred for about 10
minutes, and concentrated. Ethyl acetate is added and the mixture is heated to 40 °C for
about 10 minutes followed by concentration to ensure complete neutralization.
Cyclization is completed in substep 2b by adding ethanol and cyanogen bromide to the
residue and the mixture is heated to about 120 °C for about 4 hours. Following
evaporation of the solvent, the residue is dissolved in water and 1.0 M hydrochloric acid
and washed with ethyl acetate. The aqueous extract is treated with concentrated aqueous
hydrochloric acid and stirred at 50 °C for about 48 hours. The mixture is cooled, the pH
adjusted to basic with aqueous sodium hydroxide and extracted with ethyl acetate.
Purification of the crude aniline amino bicyclic oxazine can be accomplished with silica
gel flash chromatography eluting with a gradient such as 7 M ammonia in methanol and
dichloromethane. In step N, substep 3, this material can be amidated at the aniline amine
as described above in step M, substep 2 to give the compound of Formula II or Formula
Illb.
Alternatively one skilled in the art will recognize that there are a number of
methods and reagents for amide formation resulting from the reaction of carboxylic acids
and amines as described previously under Scheme 2 and can be applied to Scheme 3 also.
A pharmaceutically acceptable salt of a compound of Formulas I, II and III, such
as a hydrochloride salt, can be formed by reaction of an appropriate free base of Formulas
I, II, or III (including Ilia and Illb) with an appropriate pharmaceutically acceptable acid
in a suitable solvent under standard conditions well known in the art. Additionally, the
formation of such salts can occur simultaneously upon deprotection of a nitrogen
protecting group. The formation of such salts is well known and appreciated in the art.
See, for example, Gould, P.L., "Salt selection for basic drugs," International Journal of
Pharmaceutics, 33: 201-217 (1986); Bastin, R.J., etal. "Salt Selection and Optimization
Procedures for Pharmaceutical New Chemical Entities," Organic Process Research and
Development, 4 : 427-435 (2000); and Berge, S.M., et a , "Pharmaceutical Salts," Journal
of Pharmaceutical Sciences, 66: 1-19, (1977).
The following preparations and examples further illustrate the invention.
Preparation 1
2-(Allyloxy)-N-methoxy-N-methylacetamide
O
/
Scheme 1, steps A and B: Bromoacetyl bromide (1.06 equiv.) is added to a
solution of N,0-dimethylhydroxylamine hydrochloride (1.0 equiv.) (Volumes are in mL/g
of this compound) in a stirring mixture of water (4 mL/g), toluene (4 mL/g), and K2C0 3
(1.15 equiv.) at 0 °C. After warming to room temperature over 1 hour, the layers are
separated and the aqueous layer is extracted with toluene (2 mL/g). The combined
organic layers are concentrated to give the intermediate 2-bromo-N-methoxy-N-methylacetamide
containing about 20% toluene. 2-Bromo-N-methoxy-N-methyl-acetamide is
added to a mixture of allyl alcohol (6.3 equiv) and K2C0 3 (2 equiv.) over 3 hours at 30 °C.
After 2 hours at 30 °C, toluene (4 mL/g) is added, the mixture is cooled to 0 °C, and
filtered. The filter cake is rinsed with cold (0 °C) toluene (2.7 mL/g) and the combined
filtrate is washed with a 3 weight % solution of KHS0 4 in water (0.6 mL/g). The toluene
solution is concentrated while additional toluene (11 mL/g) is added to remove water and
allyl alcohol. The concentrated toluene solution is washed with water (0.5 g/g), further
concentrated to remove most of the toluene, and then distilled to give the title compound.
LC-MS (m/z): 160 (M+H).
Preparation 2
(3aS,6aS)-6a-(5-Bromo-2-fluorophenyl)- 1-((R)- 1-phenylpropyl)hexahydrofuro [3,4-
cjisoxazole
Scheme 1, steps C and D: To 4-bromo-l-fluoro-2-iodobenzene (0.95 equiv.) in
THF (4.6 mL/g) at 0 °C is added isopropylmagnesium chloride (1.0 equiv, 20 weight
percent in THF). After about 60 minutes at 0 °C, a solution of 2-(allyloxy)-N-methoxy-
N-methylacetamide (1.0 equiv.) (Volumes for this stage are in mL/g of this compound) in
THF (2.2 mL/g) is added over about 60 minutes. The reaction mixture is quenched into a
solution of NH4CI (4.3 equiv.) in water (5.8 mL/g) at 0 °C. Heptanes (7.2 mL/g) is added
as the mixture is warmed to room temperature, and the layers are separated. The organic
layer is washed with water (7.2 mL/g). The organic layer is concentrated while additional
heptanes (4 mL/g) is added to remove water and THF. The intermediate, 2-allyloxy-l-(5-
bromo-2-fluoro-phenyl)ethanone is obtained as a solution in heptanes (approximately 20-
25 weight %).
(R)-N-(l-Phenylpropyl)hydroxylamine />-toluenesulfonic acid salt is treated with
KHCO3 (2.75 equiv.), water (6.6 mL/g), and methyl t rt-butylether (6.8 mL/g). The
layers are separated and the organic layer is washed with a 25 weight % solution of NaCl
(2.8 mL/g) in water. Heptanes (12 mL/g) is added and most of the MTBE and water are
removed by distillation at about 50 °C. A 20-25 weight % solution of 2-allyloxy-l-(5-
bromo-2-fluoro-phenyl)ethanone ( 1 equiv., volumes for this stage are in mL/g of this
compound) in heptanes is added to the (R)-N-(l-phenylpropyl)hydroxylamine heptanes
mixture at 50 °C. Titanium tetraisopropoxide ( 1.5 equiv.) is added and the mixture is
heated at about 55-60 °C for about 10 hours. The mixture is concentrated at about 35 -
50 °C while additional heptanes (6 mL/g) is added. The distillation is stopped when the
total volume is about 5 mL/g compared to the expected product yield of 60%. The
mixture is cooled to -10 °C, the solids are collected by filtration, rinsed twice with cold (-
10 °C) heptanes ( 1 mL/g) and dried to give the title compound. LC-MS (m/z for
7 Br/ 1Br): 406/408 (M+H).
Preparation 3
N-(4-Fluoro-3-((3aS,6aS)-l-((R)-l-phenylpropyl)hexahydrofuro[3,4-c]isoxazol-6ayl)
phenyl)acetamide
Scheme 1, step E: A mixture of (3aS,6aS)-6a-(5-bromo-2-fluorophenyl)-l-((R)-lphenylpropyl)
hexahydrofuro[3,4-c]isoxazole (1.0 equiv., volumes are in mL/g of this
compound), acetamide (4 equiv.), copper (I) iodide (0.2 equiv.), potassium iodide (0.7
equiv.), K3P0 4 (2.0 equiv.), N^V-dimethylethylenediamine (0.8 equiv.) and DMF (4
mL/g) is heated at 110 °C for about 4 hours. After cooling to 30 °C, the mixture is
partitioned between isopropyl acetate (3.7 mL/g) and 10 weight %¾ (5.7 mL/g) in
water. The layers are separated and the aqueous layer is extracted with isopropyl acetate
(2 mL/g). The combined organic layers are washed twice with 10 weight % NH4C 1 ( 1
mL/g) in water. The organic layer is mixed with xylenes (4.3 mL/g), and the mixture is
distilled under vacuum to remove most of the isopropyl acetate and residual DMF. The
mixture is cooled to 0 °C, the solids are collected by filtration, rinsed twice with xylenes
(0.7 mL/g) and dried to give the title compound. LC-MS (m/z): 385 (M+H).
Preparation 4
N-(3-((3S,4R)-3-Amino-4-(hydroxymethyl)tetrahydrofuran-3-yl)-4-
fluorophenyl)acetamide hydrochloride
HCI
Scheme 1, step F: A mixture of N-(4-fluoro-3-((3aS,6aS)-l-((R)-lphenylpropyl)
hexahydrofuro[3,4-c]isoxazol-6a-yl)phenyl)acetamide ( 1.0 equiv.,
volumes are in mL/g of this compound), zinc chloride (0.2 equiv), and a 20% weight
loading of water wet, sulfided 5% Pd/C catalyst is slurried in a mixture 1-propanol (4
mL/g), water (3.8 mL/g), and HCI (0.9 equiv, 33 weight % in water). The mixture is
heated at 50 °C under hydrogen pressure (about 300-400 kPa) for about 16 hours.
The catalyst is removed by filtration at about 50 °C and the filter cake is rinsed with
1-propanol (2.9 mL/g). Most of the water is removed from combined filtrates by
azeotropic distillation using additional 1-propanol (10.5 mL/g). Additional HCI (0.1
equiv., 33 weight % in water) is added to the mixture and the solids are collected by
filtration, rinsed twice with 1-propanol ( 1 mL/g) and dried to give the title compound.
LC-MS (m z): 269 (M+H).
Preparation 5
rt-Butyl N-[(3S,4R)-3-(5-acetamido-2-fluoro-phenyl)-4-
(hydroxymethyl)tetrahydrofuran-3-yl]carbamate
Method A
Scheme 1, step G substep 1 (protection): A solution of N-[3-[(3S,4R)-3-amino-4-
(¾ydroxymethyl)tetrahydrofuran-3-yl]-4-fluoro-phenyl]acetamide hydrochloride (60.0 g,
197 mmol), triethylamine (85.0 mL, 610 mmol) and di-t r t-butyl dicarbonate (60.0 g, 272
mmol) in tetrahydrofuran at 50 °C is stirred for 15.5 hours. The reaction is cooled to
ambient temperature, filtered, washed with ethyl acetate, and concentrated under reduced
pressure. The residue is purified by silica gel flash chromatography, eluting with
methanol/dichloromethane (0:10) to methanol/dichloromethane (1:10) to give the title
compound (71.0 g, 98%). ES/MS (m/e): 269 (M-99).
Method B Preparation 5
Di-t rt-butyldicarbonate (130 g, 591 mmol) is added to a solution of N-(3-
((3S,4R)-3-amino-4-(hydroxymethyl)te1rahydrofuran-3-yl)-4-fluorophenyl)acetamide
hydrochloride (150 g, 492 mmol) and triethylamine (137 mL, 984 mmol) in THF (1.2 L).
After stirring at 50 °C under nitrogen for 18 hours, the reaction mixture is gradually
cooled to room temperature and the solvent is evaporated. The residue is partitioned
between 10% citric acid aqueous solution (500 mL) and ethyl acetate ( 1 L). The layers
are separated and the aqueous layer is extracted with ethyl acetate (2 150 mL). The
organic layers are combined, dried over sodium sulfate, filtered and concentrated under
reduced pressure to give a residue which is dried under vacuum to constant weight to give
the title compound (192 g, 95.3%). ES/MS (m z): 367(M+1), 267 (M-99); l NMR
(300.16 MHz, CDC13) 7.85-7.79 (m, 1H), 7.60-7.56 (m, 1H), 7.41-7.36 (m, 1H), 7.26
(d, J= 1.0 Hz, 7H), 7.04-6.95 (m, 2H), 4.26-4.11 (m, 2H), 3.80-3.72 (m, 3H), 2.15 (s, 5H),
2.05 (d, J= 0.8 Hz, 1H), 1.72-1.67 (m, 1H), 1.36 (s, 13H), 1.31-1.26 (m, 3H).
Preparation 6
t rt-Butyl N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-formyl-te1rahydrofuran-3-
yl]carbamate
Method A
Scheme 1, step G, substep 2 (oxidation): A mixture of pyridinium chlorochromate
(10.0 g, 45.5 mmol), 4A molecular sieves (20.0 g) and ammonium acetate (5.00 g, 62.3
mmol) are grinded into a fine powder and added to dichloromethane (150 mL). A
solution of t r t-butyl N-[(3S,4R)-3-(5-acetamido-2-fluoro-phenyl)-4-
(hydroxymethyl)tetrahydrofuran-3-yl]carbamate (10.0 g, 27.1 mmol) in dichloromethane
(100 mL) is then added. The resulting suspension is stirred at ambient temperature for 35
minutes and is concentrated under reduced pressure to approximate 100 mL volumes of
dichloromethane. Ethyl acetate (200 mL) is then added, and the resulting mixture is
filtered through a silica gel cake. The cake is washed with ethyl acetate, and the
combined filtrate is concentrated under reduced pressure to give the title compound (71.0
g, 98%), which is used without further purification. ES/MS (m/e): 267 (M-99).
Method B Preparation 6
2-Iodosobenzoic acid (45% w/w, 88.3 g, 142 mmol) is added portion wise to a
solution of t r t-butyl N-[(3S,4R)-3-(5-acetamido-2-fluoro-phenyl)-4-
(hydroxymethyl)tetrahydrofuran-3-yl]carbamate (50.0 g, 129 mmol) in DMSO (200 mL)
at room temperature. After stirring at 22 °C for 18 hours, the reaction mixture is added to
a sodium carbonate aqueous solution (500 mL) keeping the temperature below 25 °C.
Methyl-t-butyl ether is added (500 mL) and the mixture is stirred at room temperature for
15 minutes. The mixture is filtered through diatomaceous earth and the organic layer is
separated. The aqueous layer is extracted with methyl-t-butyl ether (2 x 100 mL). The
organic layers are combined, dried over sodium sulfate, filtered, and concentrated under
reduced pressure to give a residue. The residue is dried under vacuum to a constant
weight (46.0 g, 93.5%). This material is used without further purification. ES/MS (m/z):
267(M-99). l NMR (300.16 MHz, CDC13) 9.87 (d, J= 2.8 Hz, 1H), 9.44 (t, J= 2.2 Hz,
1H), 7.63-7.55 (m, 3H), 7.43-7.31 (m, 2H), 7.26 (s, 3H), 7.04-6.98 (m, 2H), 5.30 (s, 1H),
4.49-4.28 (m, 5H), 4.12-4.06 (m, 2H), 3.75 (td, J= 7.6, 2.6 Hz, 1H), 3.21 (s, 4H), 2.62 (s,
1H), 2.15 (d, J= 4.4 Hz, 6H), 1.63 (s, 4H), 1.36-1.31 (m, 18H), 1.19 (s, 11H).
Preparation 7
rt-Butyl N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-fluoro-4-
(hydroxymethyl)tetrahydrofuran-3-yl]carbamate
Method A
Scheme 1, step H, substeps 1 and 2 (fluorination and reduction): A solution of
t r t-butyl N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-formyl-tetrahydrofuran-3-
yljcarbamate (9.0 g, 24.56) in tetrahydrofuran (100 mL) is treated with pyrrolidine (2.20
mL, 26.4 mmol). The resulting solution is stirred at ambient temperature for 7 minutes
and is treated with l-chloromethyl-4-fluoro-l,4-diazoniabicyclo[2.2.2]octane
bis(tetrafluoroborate) (10.0 g, 28.2 mmol). The reaction is stirred at ambient temperature
for 160 minutes, then is quenched with a solution of saturated sodium bicarbonate in
water, and is extracted with ethyl acetate and dichloromethane consecutively. The
organic layers are combined, dried over magnesium sulfate, filtered, and concentrated
under reduced pressure to give a residue. The residue is dissolved in methanol (100 mL)
and sodium borohydride (1.00 g, 26.2 mmol) is added in a single portion to the solution.
The resulting reaction is stirred at ambient temperature for 37 minutes, quenched with a
solution of saturated sodium bicarbonate in water, and extracted with dichloromethane
and ethyl acetate consecutively. The organic layers are combined, dried, filtered, and
concentrated under reduced pressure to give a residue. The residue is purified by silica
gel flash chromatography, eluting with methanol/dichloromethane (0:10) to
methanol/dichloromethane (1:10) to give the title compound (2.70 g, 28%). ES/MS
(m/e): 287 (M-99).
Method B Preparation 7
D-(+)-Proline (691 mg, 6.00 mmol) is added in a single portion to a solution of
t r t-butyl N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-formyl-tetrahydrofuran-3-
yljcarbamate (2.00 g, 5.46 mmol) in 2,2,2-trifluoro-ethanol (16 mL, treated with
potassium carbonate and 3A molecular sieves, and filtered prior to use). 3A Molecular
sieves (500 mg) are added and the reaction mixture is stirred at room temperature for 4
hours. To the reaction mixture is added l-(chloromethyl)-4-fluoro-l,4-
diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (2.51 g, 7.10 mmol) in a single
portion and the mixture is stirred at room temperature for 36 hours. The solvent is
concentrated under vacuum and the residue is partitioned between water (25 mL) and
ethyl acetate (25 mL). Sodium bicarbonate (7% aqueous solution) is added to adjust
pH=8 and the organic layer is separated. The aqueous layer is extracted with ethyl acetate
(2 15 mL). The organic layers are combined, dried over sodium sulfate, filtered, and
concentrated under reduced pressure. The residue is dissolved in ethanol (25 mL) and
sodium tetrahydroborate (289 mg, 7.64 mmol) is added. After stirring at room
temperature for 2 hours, the solvent is evaporated under vacuum and the residue is
partitioned between water (30 mL) and ethyl acetate (30 mL). The organic layer is
separated, dried over sodium sulfate and filtered. The filtrates are evaporated under
reduced pressure. The residue is purified by silica gel flash chromatography, eluting with
ethyl acetate/hexane (1:1) to ethyl acetate to give the title compound (1.50 g, 70.0%) as a
white foam. ES/MS (m z): 287(M-99). l NMR (300.13 MHz, CDC13) 7.99-7.89 (m,
1H), 7.81-7.74 (m, 1H), 7.49-7.46 (m, 1H), 7.26 (s, 2H), 6.98 (dd, J= 9.0, 12.0 Hz, 1H),
5.79-5.74 (m, 1H), 4.39-4.34 (m, 1H), 4.32-4.27 (m, 2H), 2.14 (s, 4H), 1.71 (s, 3H).
Method C Preparation 7
D-(+)-Proline (36 g, 313.1 mmol) is added in a single portion to a solution oitertbutyl
N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-formyl-te1rahydrofuran-3-
yljcarbamate (95.6 g, 260.9 mmol) in methanol (956 mL) and the reaction mixture is
stirred at room temperature for 16 hours. To the reaction mixture is added 1-
(chloromethyl)-4-fluoro-l,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (120.1 g,
339.2 mmol) in a single portion and the mixture is stirred at room temperature for 24
hours. The solvent is concentrated under vacuum and the residue is partitioned between
sodium bicarbonate (7% aqueous solution) (800 mL) and ethyl acetate (600 mL). The
aqueous layer is extracted with ethyl acetate (2 300 mL). The organic layers are
combined, dried over sodium sulfate, filtered, and concentrated under reduced pressure.
The residue is dissolved in ethanol (956 mL) and sodium tetrahydroborate (13.80 g, 365.2
mmol) is added. After stirring at room temperature for 2 hours, the solvent is evaporated
under vacuum and the residue is partitioned between water (500 mL) and ethyl acetate
(500 mL). The organic layer is separated, dried over sodium sulfate, filtered and
concentrated to dryness. The residue is purified by silica gel flash chromatography,
eluting with ethyl acetate/hexane ( 1:1) to ethyl acetate to give the title compound (55g,
54%) as a white foam. ES/MS (m/z): 287(M-99). 1H NMR (300.13 MHz, CDC13) 
7.99-7.89 (m, 1H), 7.81-7.74 (m, 1H), 7.49-7.46 (m, 1H), 7.26 (s, 2H), 6.98 (dd, J= 9.0,
12.0 Hz, 1H), 5.79-5.74 (m, 1H), 4.39-4.34 (m, 1H), 4.32-4.27 (m, 2H), 2.14 (s, 4H), 1.71
(s, 3H).
Preparation 8
N-[[(3S,4S)-3-(5-Acetamido-2-fluoro-phenyl)-4-fluoro-4-
(¾ydroxymethyl)te1rahydroiuran-3-yl]carbamothioyl]benzamide
Scheme 2, step I, (deprotection and thiourea formation): A solution of t rt-butyl
N-[(3S,4S)-3-(5-acetantido-2-fluoro-phenyl)-4-fluoro-4-(¾ydroxymethyl)tetrahydrofuran-
3-yl]carbamate (2.70 g, 6.99 mmol) in dichloromethane (40 mL) and trifluoroacetic acid
(8.00 mL, 106 mmol) is stirred at ambient temperature for 150 minutes. The reaction is
concentrated under reduced pressure and azeotroped with toluene. The residue is
dissolved in tetrahydrofuran and treated with triethylamine (1.10 mL, 7.89 mmol) and
benzoyl isothiocyanate (1.00 mL, 7.41 mmol). The reaction is stirred at ambient
temperature for 16.5 hours and is then quenched with a solution of saturated sodium
bicarbonate in water, extracted with ethyl acetate and dichloromethane consecutively.
The organic layers are combined, dried over magnesium sulfate, filtered, and
concentrated under reduced pressure to give a residue. The residue is purified by silica
gel flash chromatography, eluting with methanol/dichloromethane (0:10) to
methanol/dichloromethane (1:10) to give the title compound (2.60 g, 83%). ES/MS
(m/e): 450 (M+l).
Preparation 9
N-[3-[(3 S,4S)-3 -Amino-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3-yl] -4-fluorophenyljacetamide
hydrochloride
Method A
Scheme 3, step L and step N, substep 1 (deprotection): Ethanol (8.61 mL, 148
mmol) is added drop wise to a solution of acetyl chloride (9.36 mL, 131 mmol) in ethyl
acetate (127 mL) at 0 °C. After stirring at 0 °C for 30 min, t rt-butyl N-[(3S,4S)-3-(5-
acetamido-2-fluoro-phenyl)-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3-yl]carbamate
(12.7 g, 32.8 mmol) is added and then the reaction mixture is gradually warmed to room
temperature and stirred for another 18 hours. A white solid is collected by filtration and
dried under reduced pressure to constant weight to give the titled compound ( 11.0 g; 99.0
%). ES/MS (m z): 287(M-35). ^NMR (300.16 MHz, d6-DMSO) 10.31 (s, 1H), 9.05
(s, 2H), 7.85-7.83 (m, 1H), 7.75-7.71 (m, 1H), 7.31-7.22 (m, 1H), 5.15-5.07 (m, 3H),
4.48-4.33 (m, 3H), 4.12-3.97 (m, 3H), 2.50 (s, 4H), 2.05 (s, 4H), 1.98 (s, 1H), 1.59 (s,
1H).
Method B Preparation 9
Hydrochloric acid (4 M in 1,4-dioxane, 1.95 mL, 7.80 mmol) is added to a
solution of t r t-butyl N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-fluoro-4-
(hydroxymethyl)tetrahydrofuran-3-yl]carbamate (1.00 g, 2.59 mmol) in ethyl acetate (10
mL) and the mixture is stirred overnight at room temperature. The mixture is filtered and
the white precipitate is washed with ethyl acetate (10 ml) to obtain the title compound
(800 mg, 96.0 %) as a white solid. ES/MS (m/z): 287 (M+l).
Method C Preparation 9
Hydrogen chloride in isopropyl alcohol 6 M (100 ml, 600 mmol) is added drop
wise to a solution of t rt-butyl N-[(3S,4S)-3-(5-acetamido-2-fluoro-phenyl)-4-fluoro-4-
(hydroxymethyl)tetrahydrofuran-3-yl]carbamate (56 g, 144.9 mmol) in isopropyl alcohol
(225 mL). After stirring at22 °C for 16 hours, the reaction is diluted with hexanes (350
mL) and stirred an additional 30 minutes. A white solid is collected by filtration and
dried under reduced pressure to constant weight to give the title compound (36.5 g, 78%).
ES/MS (m z): 287 (M-35). l NMR (300.16 MHz, de-DMSO) 10.31 (s, 1H), 9.05 (s,
2H), 7.85-7.83 (m, 1H), 7.75-7.71 (m, 1H), 7.31-7.22 (m, 1H), 5.15-5.07 (m, 3H), 4.48-
4.33 (m, 3H), 4.12-3.97 (m, 3H), 2.50 (s, 4H), 2.05 (s, 4H), 1.98 (s, 1H), 1.59 (s, 1H).
Preparation 10
N-[(4aR,7aS)-7a-(5-Acetamido-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo[3,4-
d][1,3]thiazin-2-yl]benzamide
Method A
Scheme 2, step J (cyclization): A solution of N-[[(3S,4S)-3-(5-acetamido-2-
fluoro-phenyl)-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3-
yl]carbamothioyl]benzamide (2.60 g, 5.78 mmol) and l-chloro-N,N,2-
trimethylpropenylamine (1.10 mL, 8.31 mmol) in dichloromethane (50 mL) is stirred at
ambient temperature for 190 minutes. The reaction is quenched with a solution of
saturated sodium bicarbonate in water, and extracted with dichloromethane. The organic
layers are combined, dried over magnesium sulfate, filtered, and concentrated under
reduced pressure to give a residue. The residue is purified by silica gel flash
chromatography, eluting with ethyl acetate/hexane (0: 1) to ethyl acetate/hexane ( 1:0) to
give the title compound (1.36 g, 54%). ES/MS (m/e): 432.0 (M+l).
Method B Preparation 10
A solution of N-[3- [(3 S,4S)-3 -amino-4-fluoro-4-(¾ydroxymethyl)tetrahydrofuran-
3-yl]-4-fluoro-phenyl]acetamide hydrochloride (14.5 g, 40.44 mmol) in THF (290 mL) is
treated with triethylamine (5.64 mL, 40.44 mmol) and the mixture is stirred for 15
minutes and then cooled to 5 °C. Benzoyl isothiocyanate (6 mL, 44.48mmol) is added
and the reaction is warmed to room temperature over 3 hours. l,l'-Carbonyldiimidazole
(7.21 g, 44.48 mmol) is added and the reaction mixture is stirred at room temperature for
16 hours, and then refluxed for 72 hours. The reaction mixture is cooled to 22 °C and
then poured into water (150 mL) and MTBE (200 mL). The organic layer is separated
and the aqueous layer is washed with MTBE (2 x 100 mL). The organic layers are
combined, dried over sodium sulfate, filtered and evaporated to a residue. The residue is
purified by silica gel chromatography eluting with methylene chloride/ethyl acetate (1/1)
to give the title compound as white foamy solid (10.5 g, 60%). ES/MS (m e): 328.0
(M+l).
Preparation 11
N-[(4aR,7aS)-7a-(5-Acetamido-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo[3,4-
d][1,3]oxazin-2-yl]benzamide
Method A
F
Scheme 3, step L, substep 2a and b (neutralization, thiourea formation and
cyclization): Triethylamine (1.90 mL, 13.6 mmol) is added to a solution of N-[3-
[(3S,4S)-3-amino-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3-yl]-4-fluorophenyl]
acetamide hydrochloride (4.00 g, 12.4 mmol) in acetonitrile (40 mL) at 5 °C under
nitrogen. After stirring for 30 min benzoyl isothiocyanate (1.76 mL, 13.0 mmol) is added
drop wise. The resulting mixture is stirred at 5 °C for 1 hour. Trimethylsilyl chloride
(1.73 mL, 13.6 mmol) and DMSO (968 , 13.6 mmol) are added and the mixture is
stirred at 5 °C for 2 hours. The reaction mixture is poured into an aqueous solution of
potassium phosphate dibasic (20%, 150 mL) to reach pH 7-8 and stirred for 30 min.
Ethyl acetate (50 mL) is added and the mixture is filtered through diatomaceous earth.
The organic layer is separated, and the aqueous layer is extracted with ethyl acetate (50
mL). The organic layers are combined, washed with brine, dried over magnesium sulfate,
and filtered. The filtrates are evaporated under reduced pressure and the residue is
purified by silica gel flash chromatography eluting with ethyl acetate/hexane (60%) to
ethyl acetate/hexane (90%) to give the title compound (3.50 g, 68.0 %) as white solid.
ES/MS (m z): 416 (M+l).
Method B Preparation 11
Scheme 3, step L, substeps 2a and b (neutralization, N-carbamoyl benzamide
formation, and cyclization): A mixture of N-[3-[(3S,4S)-3-amino-4-fluoro-4-
(¾ydroxymethyl)tetrahydrofuran-3-yl]-4-fluoro-phenyl]acetamide hydrochloride (12 g,
37.19 mmol), triethylamine (5.7 mL, 4 1 mmol), and phenyl N-benzoylcarbamate (9.9 g,
4 1 mmol) are dissolved in THF (240 mL) and the mixture is heated at 70 °C for 2 hours.
The mixture is cooled to room temperature and extracted with ethyl acetate (500 mL),
washed with water (250 mL), brine (250 mL), dried over Na2S0 4, filtered, and
concentrated to dryness to give the intermediate thiourea. (LCMS (m z): 434 (M+H).
The crude material is dissolved in dichloromethane (240 mL) and cooled to -78 °C.
Diethylaminosulfur trifluoride (5.9 mL, 45 mmol) is added, the dry ice cooling bath is
removed and the mixture is allowed to warm to room temperature and stirred 1 hour. The
mixture is diluted with dichloromethane (500 mL) and washed with saturated aqueous
sodium bicarbonate (250 mL). The mixture is filtered through diatomaceous earth and
washed with brine (250 mL). The organic layer is dried over sodium sulfate, filtered, and
concentrated to dryness. The residue is purified with silica gel chromatography eluting
with a gradient of dichloromethane and methanol (99:1) to (95:5). The purification is
repeated on mixed fractions to give the title compound (13.5 g, 87%). LCMS (m z):
415.8 (M+H).
Preparation 1
(4aR,7aS)-7a-(5-Amino-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo[3,4-
d] [1,3]thiazin-2-amine
Method A
Scheme 2, step K, substep 1 (deprotection): A solution of N-[(4aR,7aS)-7a-(5-
acetamido-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo [3,4-d] [1,3]thiazin-2-
yllbenzamide (2.36 g, 3.15 mmol), O-methylhydroxylamine hydrochloride (1.50 g, 17.6
mmol) and pyridine (1.50 mL, 18.6 mmol) in ethanol (30 mL) is heated to 50 °C for 16
hours. Then concentrated hydrochloric acid (6.00 mL, 79.2 mmol) is added, and the
heating is continued for an additional 24 hours. The reaction is cooled to ambient
temperature and concentrated under reduced pressure. The residue is purified by silica
gel flash chromatography, eluting with 7 M ammonia in methanol/dichloromethane (0/10)
to 7 M ammonia in methanol/dichloromethane (1/10) to give the title compound (800 mg,
89%). ES/MS (m e): 286.0 (M+l).
Method B
Scheme 2, step K, substep 1 (deprotection): A solution of N-[(4aR,7aS)-7a-(5-
acetamido-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo [3,4-d] [1,3]thiazin-2-
yllbenzamide (1.20 g, 2.50 mmol), O-methylhydroxylamine hydrochloride (1.50 g, 23.5
mmol) and pyridine (2.00 mL, 24.7 mmol) in ethanol (25 mL) is heated to 50 °C for 18
hours. The reaction is then purified directly by a SCX column using methanol followed
by 7 M ammonia in methanol as the eluent to give a residue. The residue is dissolved in
ethanol (15 mL) and hydrochloric acid (3.00 mL, 39.6 mmol), and heated at 50 °C for 23
hours. The reaction is cooled to ambient temperature and concentrated under reduced
pressure. The residue is purified by an SCX column in methanol followed by 7 M
ammonia in methanol to give the title compound (640 mg, 90%). ES/MS (m/e): 286.0
(M+l).
Method C Preparation 12
A solution of N-[(4aR,7aS)-7a-(5-acetamido-2-fluoro-phenyl)-4a-fluoro-5,7-
dihydro-4H-furo[3,4-d][l,3]thiazin-2-yl]benzamide (2.15 g, 2.49 mmol), lithium
hydroxide (179 mg, 7.47 mmol) in methanol (25 mL) is heated to 50 °C for 16 hours.
Then reaction mixture is cooled to room temperature and the solvent is evaporated. The
residue is diluted with ethyl acetate (15 mL) and water (20 mL) and 2 M citric acid
aqueous solution is added to adjust the pH to 1. The aqueous layer is separated and
neutralized with NaOH 50% w/w aqueous solution until the pH=10. The reaction mixture
is washed with ethyl acetate (2 15 mL) and the organic layers are combined, dried over
sodium sulfate, and filtered. The filtrate is evaporated to give the title compound (850
mg, 89%). The crude material is used without further purification. ES/MS (m e): 286.0
(M+l).
Preparation 13
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-
fluoro-phenyl]acetamide
Method A
Scheme 3, step M, substep 1 (deprotection): N-[(4aR,7aS)-7a-(5-acetamido-2-
fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-2-yl]benzamide (3.50 g,
8.43 mmol) is added to a solution of lithium hydroxide (225mg , 9.27 mmol) in methanol
(35 mL) and the mixture is stirred at 40 °C for 18 hours. The solvent is evaporated and
the residue is partitioned between ethyl acetate (50 mL) and water (30 mL). The aqueous
layer is extracted with ethyl acetate and the organic layers are combined. The organic
solution is washed with aqueous hydrochloric acid (0.1 M, 50 mL). The aqueous layer is
then treated with aqueous sodium hydroxide solution (2.0 M) until pH=10 and is
extracted twice with ethyl acetate (2 50 mL). The organic layers are combined, dried
over magnesium sulfate, and filtered. The filtrates are evaporated under reduced pressure
to yield the title compound (1.9 g, 72 %) as a white foam. ES/MS (m/z): 312(M+1).
Method B Preparation 13
Scheme 3, step N, substeps 2a and 2b (neutralization and cyclization): A solution
of N-[3-[(3 S,4S)-3-amino-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3 -yl] -4-fluorophenyljacetamide
hydrochloride (8 g, 24.8 mmol) in THF (80 mL) is treated with
[benzoyl(phenoxycarbonyl)amino]potassium (7.62, 27.3 mmol) and the mixture is heated
at reflux for 3 hours. The reaction is cooled and the solvent is evaporated. The residue is
partitioned in water (50 mL) and ethyl acetate (100 mL) and the aqueous layer is
discarded. The organic layer is washed with brine, dried over magnesium sulfate, and
filtered. The filtrate is evaporated and the residue is dried under vacuum to a constant
weight. The crude material is dissolved in methylene chloride (120 mL) and then cooled
to -35 °C under a nitrogen atmosphere. Diethylaminosulfur trifluoride (3.94 mL, 29.75
mmol) is added keeping the internal temperature at -35 °C. The mixture is stirred 1 hour
at this temperature and then warmed to 22 °C for 2 hours. The reaction is poured into
potassium dibasic phosphate aqueous solution (200 mL) and methylene chloride (50 mL).
The organic layer is separated, washed with brine, dried over magnesium sulfate, and
filtered. The filtrate is evaporated and dried under vacuum to a constant weight. This
crude material is dissolved in methanol (80 mL) and lithium hydroxide (783 mg, 32.2
mmol) is added. The mixture is heated at 50 °C during for 16 hours. The methanol is
evaporated and the residue is poured into water (50 mL) and ethyl acetate (100 mL). The
organic layer is separated and the aqueous layer washed with additional ethyl acetate (100
mL). The organic layers are combined and washed with hydrochloric acid 0.5 M (2 x 30
mL). The aqueous layers are combined and sodium hydroxide is added to adjust the
pH=10, and the aqueous mixture is extracted with ethyl acetate (2 x 50 mL). The organic
layers are combined, dried over magnesium sulfate, and filtered. The filtrate is
evaporated to dryness and the residue is dried under vacuum to a constant weight to give
the title compound (5.5 g; 7 1 % overall yield three steps). ES/MS (m/z): 312(M+1).
Preparation 14
(4aR,7aS)-7a-(5-Amino-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4H-furo[3,4-
d][1,3]oxazin-2-amine
Method A
Scheme 3, step M, substep 1 (deprotection): N-[3-[(4aR,7aS)-2-amino-4a-fluoro-
5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-fluoro-phenyl]acetamide (800 mg, 2.57
mmol) is added to aqueous hydrogen chloride (1.0 M, 10 ml) and the resulting solution is
heated at 90 °C for 3 hours. The reaction is cooled to 22 °C and washed with ethyl acetate
(5 mL). The aqueous layer is separated and treated with aqueous sodium hydroxide
solution (1.0 M) until pH=10 and is extracted with ethyl acetate (2 5 mL). The organic
layers are combined, dried over magnesium sulfate, and filtered. The filtrates are
evaporated under reduced pressure to yield the title compound (650 mg, 2.34 mmol).
ES/MS (m z): 270 (M+l).
Method B Preparation 14
Scheme 3, step N, substeps 2a and b (neutralization and cyclization):
Triethylamine (0.32 mL, 2.3 mmol) is added to a solution of N-[3-[(3S,4S)-3-amino-4-
fluoro-4-(¾ydroxymethyl)te1rahydrofuran-3-yl]-4-fluoro-phenyl]acetamide hydrochloride
(600 mg, 1.85 mmol) in dichloromethane (10 mL). The mixture is stirred at room
temperature for 10 minutes and concentrated. Ethyl acetate (10 mL) is added to the
residue, and the mixture is heated to 40 °C for 10 minutes. The mixture is filtered and the
filtrate is concentrated and added to a 40 mL screw cap vessel. Absolute ethanol (12 mL)
and cyanogen bromide (305 mg, 2.79 mmol) are added, and the mixture is heated to 120
°C for 4 hours. The solvent is evaporated to dryness. Water (20 mL) and aqueous
hydrochloric acid ( 1.0 M, 20 mL) are added. The resulting mixture is washed with ethyl
acetate (40 mL). The aqueous layer is treated with concentrated aqueous hydrochloric
acid (3.2 mL) and stirred at 50 °C for 48 hours. The mixture is cooled to room
temperature and the pH is adjusted to basic using aqueous sodium hydroxide solution (2.0
M). The mixture is then extracted with ethyl acetate (200 mL). The organic layer is
washed with brine (100 mL) and dried over sodium sulfate, filtered, and concentrated.
The residue is purified by silica gel flash chromatography eluting with a gradient of 7 M
ammonia in methanol/dichloromethane (98:2) to 7 M ammonia in
methanol/dichloromethane (90:10) to give the title compound (175 mg, 35%) as a white
solid. ES/MS (m z): 270 (M+l).
Method C Preparation 14
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]acetamide (17 g, 54.6 mmol) is added to aqueous hydrogen chloride
(1.0 M, 218 ml) and the resulting solution is heated at 90 °C for 3 hours. The reaction is
cooled to 5 °C and sodium hydroxide 50% w/w aqueous solution is added to adjust
pH=10. The mixture is washed with ethyl acetate (3 100 mL). The organic layers are
separated, dried over magnesium sulfate, and filtered. The filtrates are evaporated under
reduced pressure to give the title compound as a white solid (13.4 g, 91%). ES/MS (m/z):
270 (M+l).
Preparation 15
N-[3-[(4aR,7aS)-2-Arrdno-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-
fluoro-phenyl]-5-cyano-pyridine-2-carboxamide
Method A
Scheme 3, steps M, substep 2 or step N, substep 3 (amidation):
Dimethylformamide (20 , 0.26 mmol) and oxalyl chloride (162 , 1.87 mmol) is
added to a slurry of 5-cyanopyridine-2-carboxylic acid (310 mg, 2.00 mmol) in
acetonitrile (10 mL) and stirred at room temperature for about 10 minutes. This mixture
is then added in a single portion to a 50 °C solution of (4aR,7aS)-7a-(5-amino-2-fluorophenyl)-
4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-2-amine (500 mg, 1.86 mmol)
in ethanol (5 mL) and water (5 mL) and the temperature is maintained at 50 °C. The
reaction mixture is stirred for about 10 minutes and quenched with saturated aqueous
sodium bicarbonate solution. The mixture is then extracted with ethyl acetate. The
organic layer is dried over sodium sulfate, filtered, and concentrated to give a residue,
which is purified by silica gel flash chromatography eluting with a gradient of 0 to 10%
MeOH in dichloromethane and further purified twice using a gradient of 7 M ammonia in
methanol/dichloromethane (5/95) to give the title compound (470 mg, 63%). ES/MS
(m z): 400 (M+l).
Method B Preparation 15
To a solution of (4aR,7aS)-7a-(5-amino-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-
4H-furo[3,4-d][l,3]oxazin-2-amine (11.6 g, 41.8 mmol) in a mixture of water (81 mL)
and ethanol (116 mL), is added hydrogen chloride 1M in water (41.7 mL, 41.7 mmol).
l-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (8.41g, 43.8 mmol) and
5-cyanopyridine-2-carboxylic acid (6.5 g, 43.8 mmol) are added in one portion and the
reaction is stirred at room temperature for 3 hours. Additional l-(3-
dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (10 mg, 52.16 ΐ) is added
and the mixture is stirred for 30 minutes. The reaction mixture is heated at 50 °C and all
the solids are dissolved. Sodium hydroxide, 1M in water (45.97 mL, 45.97 mmol) is
added drop wise keeping the temperature at 50 °C and adjusting pH to 11. The reaction is
cooled to room temperature and a white solid is collected by filtration and washed with
water. The solid is dried under vacuum to a constant weight and then purified by silica
gel chromatography eluting with a mixture of methylene chloride/methanol (95:5) to give
the title compound (7.5 g, 45%) as white solid. ES/MS (m z): 400 (M+l).
Preparation 16
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-
fluoro-phenyl] -5-chloro-pyrazine-2-carboxamide
Scheme 3, steps M, substep 2 or step N, substep 3 (amidation): A mixture of 5-
chloropyrazine-2-carboxylic acid (1.53 g, 9.66 mmol) in acetonitrile (15 mL, 283 mmol)
is treated with DMF (115 , 1.49 mmol) and oxalyl chloride (970 , 11.1 mmol). The
mixture is stirred at ambient temperature under nitrogen for 20 minutes. In a separate
flask is added (4aR,7aS)-7a-(5-amino-2-fluoro-phenyl)-4a-fluoro-5,7-dihydro-4Hfuro[
3,4-d][l,3]oxazin-2-amine (2.00 g, 7.43 mmol), ethanol (7.4 mL), water (7.4 mL)
and the mixture is heated at 50 °C. The acid chloride is added to the solution prepared
above and the reaction mixture is stirred at 50 °C for 20 minutes. The reaction is cooled
to room temperature, diluted with ethyl acetate (200 mL), and washed with water (40 mL)
and saturated aqueous NaHC0 3 (40 mL). The aqueous washes are combined and
extracted with ethyl acetate (100 mL). The combined organic layers are dried (Na2S0 4)
and the solvent removed in vacuo to give the crude product. The crude product is
purified by silica gel flash chromatography, eluting with ethyl acetate to give the title
product (2.85 g, 94%). ES/MS (m/e): 410 (M+l)
Preparation 17
5-(Cyclopropylmethoxy)pyrazine-2-carboxylic
A solution of 5-chloropyrazine-2-carboxylic acid (1.00 g, 6.31 mmol),
cyclopropyl carbinol (1.00 mL, 12.4 mmol) and potassium t rt-butoxide (2.00 g, 17.8
mmol) in dimethylformamide (20.0 mL) is heated at 100 °C for 3 hours. The reaction is
cooled to room temperature, quenched with 1M hydrochloric acid. The mixture is
extracted with ethyl acetate and isopropyl alcohol/chloroform (1/10), dried over
magnesium sulfate, filtered, and concentrated under reduced pressure to give the title
compound (1.10g, 90%) as a grayish solid. This acid is used directly without further
purification.
Preparation 18
Methyl 5-(cyclopropoxy)pyrazine-2-carboxylate
Cyclopropanol (542 , 8.69 mmol) is added to a suspension of methyl 5-
chloropyrazine-2-carboxylate (1.0 g, 5.79 mmol) and potassium carbonate (1.60 g, 11.59
mmol) in dimethylformamide ( 11.6 mL). The reaction mixture is stirred for 15 hours at
room temperature then for 24 hours at 50 °C. The reaction is cooled to ambient
temperature, diluted with water, and extracted with ethyl acetate (3 times). The organic
layers are combined, dried over sodium sulfate, filtered, and concentrated under reduced
pressure to give a brown oil. The crude product is purified by silica gel flash
chromatography, eluting with ethyl acetate/hexane (0:100) to ethyl acetate/hexane (35:65)
to give the title compound (610 mg, 54%). ES/MS (m e): 195.0 (M+l).
Preparation 19
5-(Cyclopropoxy)pyrazine-2-carboxylic
Lithium hydroxide (264 mg, 6.28 mmol) is added to a solution of methyl 5-
(cyclopropoxy)pyrazine-2-carboxylate (610 mg, 3.14 mmol) in tetrahydrofuran (10 mL)
and water (0.5 mL). The reaction mixture is stirred for 1 hour at 50 °C, cooled to ambient
temperature, diluted with water, brought to pH = 2 by slow addition of 1M HC1, and
extracted with dichloromethane (4 times). The organic layers are combined, dried over
sodium sulfate, filtered, and concentrated under reduced pressure to give the title
compound (550 mg, 97%). ES/MS (m/e): 181.0 (M+l).
Preparation 20
5-(Oxetan-2-ylmethoxy)pyrazine-2-carboxylic
In a microwave vial 5-chloropyrazine-2-carboxylic acid (100.0 mg, 0.631 mmol),
dimethylformamide (5 mL), oxetan-2-ylmethanol (83.4 mg, 0.946 mmol) and potassium
t r t-butoxide (176.9 mg, 1.58 mmol) are added. A small exotherm is observed. After 1
minute at room temperature the vial is sealed and the mixture heated at 120 °C for 30
minutes in the microwave. The reaction mixture is then quenched with aqueous NH4CI
and the solvent evaporated under reduced pressure. The resultant residue is triturated in
2-propanol. The filtrate is concentrated under reduced pressure to give the title
compound as a cream solid (0.294 g, 99%) and is used without further purification.
ES/MS (m e): 211.0 (M+l), 208.8 (M-H).
Preparation 2 1
5-(2,2-difluoroethoxy)pyrazine-2-carboxylic acid
Potassium t rt-butoxide (4.25 g, 37.84 mmol) is added to a solution of 5-
chloropyrazine-2-carboxylic acid (1.00 g, 6.31 mmol) and difluoroethanol (2.59 g, 31.54
mmol) in DMF (20 mL) and the mixture is heated at 100 °C for 2 hours. The reaction is
cooled to room temperature and stirred overnight under nitrogen. The reaction is
quenched with 1M HC1 (30 mL) and extracted with ethyl acetate (3 times). The
combined organic layers are dried over sodium sulfate, filtered, and concentrated to give
the crude product. The crude product is purified by silica gel flash chromatography,
eluting with a gradient of 0.5% to 10% methanol in dichloromethane and azeotroped with
xylenes to remove residual DMF to give the title product (1.18 g, 91%). ES/MS (m/e):
205.0 (M+l).
The following compounds in Table 1 are prepared in a manner essentially
analogous to the method set forth in Preparation 2 1 using the appropriate alcohol.
Table 1
Preparation 28
Methyl 5-(2,2,3,3-tetrafluoropropoxy)pyridine-2-carboxylate
Methyl 5-hydroxypyridine-2-carboxylate (0.903 g, 5.90 mmol) is suspended in
acetone (7 mL) and DMF (7 mL). 325 Mesh potassium carbonate (2.44 g, 17.69 mmol) is
added in one portion and stirred at room temperature for 1.5 hours under nitrogen.
2,2,3,3-Tetrafluoropropyl tnfluoromethanesulfonate (2.02 g, 7.67 mmol) is added drop
wise and the mixture is stirred for 2 hours. The reaction mixture is diluted with ethyl
acetate and saturated NH4C 1and extracted with ethyl acetate (3 times). The combined
organic extracts are washed with brine, dried over Na2S0 4, filtered, and the solvent
removed in vacuo. The crude product is purified by silica gel flash chromatography,
eluting with a gradient of 0-20% ethyl acetate in dichloromethane to give the title
compound (1.047 g, 66%). ES/MS (m/e): 268.0 (M+l).
Preparation 29
5-(2,2,3,3-Tetrafluoropropoxy)pyridine-2-carboxylic
Lithium hydroxide (469 mg, 19.6 mmol) is added to a solution of methyl 5-
(2,2,3,3-tetrafluoropropoxy)pyridine-2-carboxy late (1.047 mg, 3.92 mmol) in THF (7
mL) and water (7 mL). The reaction mixture is stirred for 1 hour at 60 °C, cooled to
ambient temperature, quenched with 1M HCl (20 mL), diluted with brine and extracted
with dichloromethane (3 times). The organic layers are combined, dried over MgS0 4,
filtered, and concentrated under reduced pressure to give the title compound (921 mg,
93%). ES/MS (m/e): 254.0 (M+l).
Preparation 30
Ethyl 5-(2,2-difluoroethoxy)-3-fluoro-pyridine-2-carboxylate
Ethyl 3,5-difluoropyridine-2-carboxylate (0.98 g, 5.24 mmol) is dissolved in
acetonitrile (20 mL). Difluoroethanol (430 , 6.81 mmol) is added followed by
potassium carbonate (1.83 g, 13.09 mmol). The solution is stirred at room temperature
for 2 days then filtered and the filtrate is concentrated. The crude material is purified via
silica gel chromatography eluting with a 0-25-50% ethyl acetate / hexanes gradient to
give the title compound (242 mg, 18%). ES/MS (m/e): 250.0 (M+l).
Preparation 31
5-(2,2-Difluoroethoxy)-3-fluoro-pyridine-2-carboxylic
Sodium hydroxide (2 M in water, 2.43 mL, 4.86 mmol) is added to a solution of
ethyl 5-(2,2-difluoroethoxy)-3-fluoro-pyridine-2-carboxylate (242 mg, 0.97 mmol) in
THF (10 mL). The reaction is stirred at room temperature for 5 days. The reaction is
quenched by the addition of 4 M HCl in dioxane (1.25 mL, 5 mmol) and the solution is
concentrated to give the crude title compound (493 mg, 229%). ES/MS (m/e): 222.0
(M+l).
Preparation 32
2-Chloro-3-fluoro-5-(2,2,3,3-tetrafluoropropoxy)pyridine
6-Chloro-5-fluoro-pyridin-3-ol (300 mg, 2.03 mmol) is dissolved in DMF (10
mL). Potassium carbonate (562 mg, 4.07 mmol) is added followed by 2,2,3,3-
tetrafluoropropyl trifluoromethanesulfonate (591 mg, 2.24 mmol) (For preparation of this
reagent, see US20 13/143900, Ex 1). The reaction is stirred at room temperature for 18
hours then allowed to stand at room temperature for 4 days. The reaction is diluted with
aqueous NaHC0 3 and ethyl acetate. The layers are separated and the aqueous layer is
extracted with ethyl acetate (2*). The combined organic layers are washed with brine and
concentrated. The crude material is purified via silica gel chromatography using a 0-10%
ethyl acetate / hexanes gradient to give the title compound (440 mg, 83%). ES/MS (m/e):
262.0 (M+l).
Preparation 33
Methyl 3-fluoro-5-(2,2,3,3-tetrafluoropropoxy)pyridine-2-carboxylate
2-Chloro-3-fluoro-5-(2,2,3,3-tetrafluoropropoxy)pyridine (440 mg, 1.68 mmol) is
added to a Parr autoclave containing palladium (II) acetate (0.04 g, 0.18 mmol) and 1,1'-
bis(diphenylphosphino)ferrocene (0.12 g, 0.21 mmol). Acetonitrile (9 mL) is added
followed by methanol (6 mL). Triethylamine (0.6 mL, 4.3 mmol) is added and the
autoclave is sealed, purged with N2, purged with CO, and then pressurized with 100 psi
CO and heated at 100 °C for 18 hours. The solution is concentrated to give the crude
product that is purified via silica gel chromatography using a 0-25% ethyl acetate /
hexanes gradient to give the title compound (430 mg, 90%). ES/MS (m/e): 286.0 (M+l).
Preparation 34
3-Fluoro-5-(2,2,3,3-tetrafluoropropoxy)pyridine-2-carboxylic
Sodium hydroxide (2 M in water, 2 mL, 4.0 mmol) is added to a solution of
methyl 3-fluoro-5-(2,2,3,3-tetrafluoropropoxy)pyridine-2-carboxylate (430 mg, 0.1.51
mmol) in THF (15 mL). The reaction is stirred at room temperature for 18 hours. The
reaction is quenched by the addition of 4 M HC1 in dioxane (1.25 mL, 5 mmol) and the
solution concentrated to give the crude title compound (476 mg, 99%). ES/MS (m/e):
222.0 (M+l).
Preparation 35
(1-Fluorocyclopropyl)methanol
A 0 °C solution of 1-fluoro-cycloproanecarboxylic acid (0.78 g, 7.49 mmol) in
THF (8 mL) is treated drop wise with 1M borane-tetrahydrofuran complex (8.99 mL,
8.99 mmol) over 10 minutes. The reaction is warmed to room temperature and stirred
under nitrogen for 18 minutes. Additional 1M borane-tetrahydrofuran complex (3.75
mL, 3.75 mmol) is added and the reaction is stirred for 2 hours. The reaction is quenched
with water (exotherm observed) followed by 1N HC1 (25 mL). The mixture is extracted
with ethyl acetate and separated. The aqueous layer is extracted with ethyl acetate (2
times) and the organic layers combined. The combined organic layers are dried (MgS0 4),
filtered and the solvent is removed in vacuo to give the title product (0.848 g, 100%).
Preparation 36
5-(2,2,2-Trifluoroethoxy)pyrazine-2-carboxylic acid
To a solution of methyl 5-chloropyrazine-2-carboxylate (25 g, 144.87 mmol) in
DMF (250 mL) under nitrogen atmosphere is added cesium carbonate (47.2 g, 144.8
mmol) and 2,2,2-trifluoro-ethanol (15.7 mL, 217.3 mmol). The reaction mixture is stirred
72 hours at room temperature. The mixture is poured over water ( 1 L) and a pale brown
solid is collected by filtration. The solid is washed with water and dried under vacuum to
a constant weight. The dry crude material is recrystallized twice from a mixture of water
(200 mL) and isopropyl alcohol (40 ml) to yield the intermediate methyl 5-(2,2,2-
trifluoroethoxy)pyridine-2-carboxylate (15 g, 93%) as a pale cream solid and is used
without further purification. A solution of intermediate methyl 5-(2,2,2-
trifluoroethoxy)pyridine-2-carboxylate (5 g,21.17 mmol) in methanol (50 mL) and 1M
sodium hydroxide aqueous solution (42.3 mL, 42.3 mmol) is stirred at room temperature
for 2 hours. Hydrochloric acid 35% w/w is added to adjust the ph to 2. Methanol is
evaporated and a pale cream solid is isolated by filtration. The solid is washed with water
and dried under vacuum to give the title compound (3 g, 51%). ES/MS (m/z): 223.1
(M+l).
Preparation 37
5-(2,2,2-trifluoroethoxy)pyridine-2-carboxylic acid
To a solution of methyl 5-hydroxypyridine-2-carboxylate (10.1 g, 65.95 mmol)
and cesium carbonate (42.9 g, 131.9 mmol) in DMF ( 1 L) is added a solution of 2,2,2-
trifluoroethyl trifluoromethanesulfonate (22.96 g, 98.93 mmol) in 20 ml of DMF over 2
hours. The reaction is stirred 4 hours at room temperature and then poured over water ( 1
L) and stirred for additional 1 hour. A brown solid is collected by filtration and washed
with additional water. The solid is dried to a constant weight to give the intermediate
compound (10.3 g 66%) of methyl 5-(2,2,2-trifluoroethoxy)pyridine-2-carboxylate which
is used without further purification. To a solution of methyl 5-(2,2,2-
trifluoroethoxy)pyridine-2-carboxylate (4.5 g, 19.1 mmol) in methanol (45 mL) is added
sodium hydroxide 1M solution (38.2 ml, 38.2 mmol) and the reaction is stirred for 2
hours at room temperature. The pH of the reaction mixture is adjusted with HC1 35%
w/w to adjust pH=l and then the resulting solid is isolated by filtration. The solid is
washed with water and then dried under vacuum to give the title compound (3 g, 70%).
ES/MS (m z): 222.1 (M+l).
Preparation 38
[Benzoyl(phenoxycarbonyl)amino]potassium
Potassium t rt-butoxide 1.5 M solution (113.8 mL, 182 mmol) is added to a
solution of benzamide (20.36 g, 168 mmol) di-phenyl carbonate (30 g, 140 mmol) in
tetrahydrofuran (450 mL) under a nitrogen atmosphere. The reaction is stirred 16 hours
at 20 °C. A pale pink solid is collected by filtration and dried under reduced pressure to a
constant weight to give the title compound (29 g; 74 %). 1H NMR (300.16 MHz, d6-
DMSO) 7.88-7.85 (m, 2H), 7.55-7.40 (m, 3H), 7.15-7.10 (m, 2H), 6.77-6.67 (m, 3H).
Example 1
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7a-yl]-4-
fluoro-phenyl]-5-fluoro-pyridine-2-carboxamide hydrochloride
Scheme 2, step K, substep 2 (amidation): Oxalyl chloride (180 , 2.07 mmol) is
added to a solution of dimethylformamide (180 , 2.33 mmol) in acetonitrile (10 mL),
and the resulting reaction is stirred for 10 min. 5-Fluoropyridine-2-carboxylic acid (300
mg, 2.13 mmol) is added to the resulting solution. The resulting reaction is stirred for an
additional 40 minutes, and then 5.0 mL of this solution is removed via syringe and added
drop wise to a solution of (4aR,7aS)-7a-(5-amino-2-fluoro-phenyl)-4a-fluoro-5,7-
dihydro-4H-furo[3,4-d][l,3]thiazin-2-amine (330 mg, 1.04 mmol) in ethanol (6.0 mL)
and water (6.0 mL) at 50 °C. The resulting solution is heated at 50 °C for 50 minutes
before being purified by SCX columns (methanol, then 7 M ammonia in methanol) to
give a residue, which is purified again by silica gel flash chromatography, eluting with 7
M ammonia in methanol/dichloromethane (0/10) to 7 M ammonia in
methanol/dichloromethane (1/10) to give a residue, which is further purified by HPLC
using a high resolution CI8 column (Waters X-Bridge OBD 30 X 75 mm, 5 particle
size) eluting with a 15-40% gradient of acetonitrile in (10 mM ammonium bicarbonate
aqueous solution with 5% methanol). The eluent containing product is concentrated
under reduced pressure to -100 mL and is then lyophilized to give a white residue as the
free base of the desired product. This material is dissolved in 2 mL of
dichloromethane/methanol (1/1) and is treated with 1M HCI in ether (360 0.36
mmol). The sample is concentrated to give the title compound (177 mg, 38%). ES/MS
(m/e): 409.0 (M+l).
Example 2
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7a-yl]-4-
fluoro-phenyl]-5-methoxy-pyrazine-2-carboxamide hydrochloride
Scheme 2, step K (amide formation): Oxalyl chloride (127 , 1.46 mmol) is
added to a slurry of 5-methoxypyrazine-2-carboxylic acid (225 mg, 1.46 mmol) and
dimethylformamide (113 , 1.46 mmol) in acetonitrile (6 mL). The resulting reaction is
stirred for 90 min. This solution is added drop wise to a solution of (4aR,7aS)-7a-(5-
amino-2-fluoro-phenyl)-4a-iluoro-5,7-dihydro-4H-ftiro[3,4-d][l,3]thiazin-2-ami (320
mg, 1.12 mmol) in ethanol (5.5 mL) and water (5.5 mL) at 50 °C. The resulting solution
is heated at 50 °C for 5 hours. The reaction is poured into a separatory funnel containing
200 mL NaHC0 3 (aq). The sample is extracted with dichloromethane (3 200 mL). The
organic layers are combined, washed with brine, and concentrated. The crude product is
purified by silica gel flash chromatography, eluting with 7 M ammonia in
methanol/dichloromethane (0/10) to 7 M ammonia in methanol/dichloromethane (1/10).
This material is further purified by reverse phase flash chromatography using a 150 g
high resolution CI 8 column and eluting with a 5-60% gradient of ACN in (10 mM
ammonium bicarbonate aqueous solution with 5% MeOH). The eluent containing
product is isolated and extracted with a 4:1 chloroform: isopropanol solution (3 50 mL).
The organic layers are combined, washed with brine, dried over MgS0 4, filtered, and
concentrated to give the free base of the desired compound. This material is dissolved in
dichloromethane (15 mL) and is treated with 4 M HC1 in dioxane (900 , 3.6 mmol).
The sample is concentrated to give the title compound (160 mg, 31.2%). ES/MS (m/e):
422.0 (M+l).
Example 3
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-7a-yl]-4-
fluoro-phenyl]-5-cyano-pyridine-2-carboxamide hydrochloride
Scheme 2, step K (amide formation): Oxalyl chloride (60.0 , 692 ΐ ) is
added to a solution of dimethylformamide (60.0 , 776 ΐ) in acetonitrile (4.0 mL),
and the resulting reaction is stirred for 16 min. 5-Cyanopyridine-2-carboxylic acid (106
mg, 715 ΐ) is added to the resulting solution. The reaction is stirred for 33 minutes,
and 2.0 mL of this solution is removed via syringe and added drop wise to a solution of
(4aR,7aS)-7a-(5-amino-2-fluoro-phenyl)-4a-fluoro-5 ,7-dihydro-4H-furo [3,4-
d][l,3]thiazin-2 -amine ( 110 mg, 347 umol) in ethanol (2.0 mL) and water (2.0 mL) at 50
°C. The resulting solution is heated at 50 °C for 44 minutes followed by purification by
SCX columns (methanol to 7 M ammonia in methanol) to give a residue, which is
purified again by silica gel flash chromatography, eluting with 7 M ammonia in
methanol/dichloromethane (0/10) to 7 M ammonia in methanol/dichloromethane (1/10) to
give a residue as the free base of the desired product (120 mg, 83%). This material is
dissolved in 5 mL of dichloromethane/methanol (1/1) and is treated with 1M HC1 in
ether (300 , 0.30 mmol). The sample is concentrated to give the title compound (128
mg, 81.6%). ES/MS (m/e): 416.1 (M+l).
Example 4
N-[3- [(4aR,7aS)-2-Aniino-4a-fluoro-5,7-dihydro-4H-furo [3,4-d] [1,3]thiazinfluoro-
phenyl]-5-(oxetan-2-ylmethoxy)pyrazine-2-carboxamide
1-Propanephosphonic acid cyclic anhydride 50 wt% solution in ethyl acetate (8.90
1.50 mmol) is added to a microwave vial containing a mixture of (4aR,7aS)-7a-(5-
amino-2-fluoro-phenyl)-4a-iluoro-5,7-dihydro-4H-furo[3,4-d][l,3]thiazin-2-am^ (81.2
mg, 0.285 mmol), 5-(oxetan-2-ylmethoxy)pyrazine-2-carboxylic acid (140 mg, 0.300
mmol) and anhydrous dichloromethane (10 mL). The vial is sealed and the mixture
stirred at room temperature overnight. The mixture is then partitioned between water and
dichloromethane and the layers separated through a Phase Separating cartridge. Organics
are combined and the solvent evaporated under reduced pressure. The resulting oil is
dissolved in methanol, filtered, and purified by preparative-HPLC (Phenomenex Gemini
10 50*150mm C-18) (CH3CN and water with 10 mM ammonium bicarbonate, 10%
to 100% CH3CN over 10 minutes at 120 ml/min) ( 1 injection). Fractions bearing product
are concentrated to dryness overnight in a centrifugal evaporator to give the title
compound as a white solid (40 mg, 28%). ES/MS (m/e): 478.2 (M+l).
The following compounds in Table 2 are prepared in a manner essentially
analogous to the method set forth in Examples 1 to 3 utilizing the appropriately
substituted carboxylic acid for the amide formation reaction. Each of the examples
shown in Examples 1 to 3 and in Table 2 can be prepared as the free base or as a
pharmaceutically acceptable salt, such as the HC1 salt, as described in Example 3.
Table 2

Example 34
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-
fluoro-phenyl]-5-cyano-pyridine-2-carboxamide hydrochloride
Method A
The free base N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-
d][l,3]oxazin-7a-yl]-4-fluoro-phenyl]-5-cyano-pyridine-2-carboxarnide (458 mg, 1.15
mmol, prepared in preparation 15) is dissolved in dichloromethane (3 mL) and methanol
(3 mL). Hydrochloric acid (4 M in 1,4-dioxane, 380 , 1.52 mmol) is added. The
solution is evaporated to dryness to provide the title compound (380 mg, 76%) as a pale
yellow solid. ES/MS (m/z): 400 (M+l).
Method B Example 34
To a solution of N-[3-[(4aR,7aS)-2-amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-
d][l,3]oxazin-7a-yl]-4-fluoro-phenyl]-5-cyano-pyridine-2-carboxamide (9.1 g, 22.7
mmol) in methanol (182 mL) is added a solution of hydrogen chloride 1.2 M in isopropyl
alcohol (18.9 mL, 22.7 mmol). The mixture is stirred for 15 minutes. The solvent is
evaporated to give the title compound as white crystalline solid (9.8 g, 99%). ES/MS
(m/z): 400 (M+l).
Example 35
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-
fluoro-phenyl]-5-cyano-3-fluoro-pyridine-2-carboxamide hydrochloride
Scheme 3, step M, substep 2 (amidation): Dimethylformamide (10 0.14
mmol) and oxalyl chloride (119 , 1.38 mmol) is added to acetonitrile (3.7 mL) and
stirred at room temperature for 10 minutes. 5-Cyano-3-fluoro-pyridine-2-carboxylic acid
(213 mg, 1.28 mmol) is added and the mixture is stirred for another 10 minutes. This
mixture is then added in a single portion to a solution of (4aR,7aS)-7a-(5-amino-2-fluorophenyl)-
4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-2-amine (247 mg, 0.917 mmol)
in ethanol (3.7 mL) and water (3.7 mL) heated to 55 °C. The reaction mixture is stirred
for 1.5 hours and then concentrated under reduced pressure. The residue is diluted with
ethyl acetate, washed with ½ saturated sodium bicarbonate solution. The aqueous layer is
extracted with ethyl acetate, and the combined organic layers are dried over sodium
sulfate, filtered, and concentrated to give a residue, which is purified by silica gel flash
chromatography eluting with a gradient of 7 M ammonia in methanol/dichloromethane
(1/99) to 7 M ammonia in methanol/dichloromethane (10/90) to give the free base of the
title compound (328 mg, 0.786 mmol). The free base is dissolved in dichloromethane (5
mL) and methanol (0.2 mL), and treated with hydrochloric acid ( 1 M in diethyl ether, 865
x , 0.865 mmol), and concentrated under reduced pressure. Diethyl ether (3 mL) is
added to the residue and concentrated and this is repeated a second time to give the title
compound (349 mg, 0.769 mmol, 83.8%). ES/MS (m/z): 418.0 (M+l).
The following compounds listed in Table 3 are prepared in a manner essentially
analogous to the method set forth in Example 35 utilizing the appropriately substituted
carboxylic acid in the amide formation reaction. In addition, the HCI salt is prepared
from the corresponding free base in a manner analogous to the method described in
Example 35.
Table 3
ase s prepare n

Example 57
N-[3-[(4aR,7aS)-2-Aniino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-
fluoro-phenyl]-5-[(l-fluorocyclopropyl)methoxy]pyrazine-2-carboxamide hydrochloride,
N-[3-[(4aR,7aS)-2-Amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7ayl]-
4-fluoro-phenyl]-5-chloro-pyrazine-2-carboxamide (110 mg, 268. ΐ), (1-
fluorocyclopropyl)methanol (73 mg, 805 ΐ) and potassium carbonate (111 mg, 805.31
ΐ) are combined in a microwave vial. Acetonitrile (3 mL) is added and the reaction
mixture is heated at 150 °C for 1.5 hours in a microwave reactor. The reaction mixture is
diluted with ethyl acetate and the organic layer is washed with saturated aqueous
NaHC0 3 and water. The combined aqueous layers are extracted twice with ethyl acetate
dried with MgS0 4 and the solvent removed in vacuo to give the crude product. The crude
product is purified by silica gel flash chromatography, eluting with 0-3% (7 N NH3-
methanol) in dichloromethane to give the free base of the title product (37 mg, 30%). The
free base is dissolved in dichloromethane (2 mL) and treated with hydrochloric acid ( 1 M
in diethyl ether, 80 80 ΐ), and concentrated under reduced pressure to give the
title product (39 mg, 29%). ES/MS (m/e): 464 (M+l)
The following compound shown in Table 4 is prepared in a manner essentially
analogous to the method set forth in Example 57 utilizing 2-fluoroprop-2-en-l-ol. In
addition, the HC1 salt is prepared from the corresponding free base in a manner analogous
to the method described in Example 35.
Table 4
In vitro Assay Procedures:
For in vitro enzymatic and cellular assays, test compounds are prepared in DMSO
to make up a 10 mM stock solution. The stock solution is serially diluted in DMSO to
obtain a ten-point dilution curve with final compound concentrations ranging from 10 
to 0.05 nM in a 96-well round-bottom plate before conducting the in vitro enzymatic and
whole cell assays.
In vitro protease inhibition assays:
Expression and Purification of BACEl :Fc.
Human BACE1 (accession number: AF190725) is cloned from total brain cDNA
by RT-PCR. The nucleotide sequences corresponding to amino acid sequences # 1 to 460
are inserted into the cDNA encoding human IgGi (Fc) polypeptide (Vassar et al., Science,
286, 735-742 (1999)). This fusion protein of BACE1(1-460) and human Fc, named
BACEl :Fc, is constructed into the pJB02 vector. Human BACEl(l-460):Fc
(AwBACEl:Fc)is transiently expressed in HEK293 cells. 250 g cDNA of each
construct is mixed with Fugene 6 and added to 1 liter HEK293 cells. Four days after the
transfection, conditioned media are harvested for purification. AwBACEl:Fcis purified by
Protein A chromatography. The enzyme is stored at - 80 °C in small aliquots. (See Yang,
et. al., J. Neurochemistry, 91(6) 1249-59 (2004)
BACE1 FRET Assay
Serial dilutions of test compounds are prepared as described above. Compounds
are further diluted 20 in KH2PO4 buffer. Ten ΐ of each dilution is added to each well
on row A to H of a corresponding low protein binding black plate containing the reaction
mixture (25 of 50 mM KH2P0 4, pH 4.6, 1mM TRITON® X-100, 1 mg/mL Bovine
Serum Albumin, and 15 of FRET substrate) (See Yang, et. a , J. Neurochemistry,
91(6) 1249-59 (2004)). The content is mixed well on a plate shaker for 10 minutes.
Fifteen of two hundred pM human BACEl(l-460):Fc (See Vasser, et a , Science,
286, 735-741 (1999)) in the KH2P0 4 buffer is added to the plate containing substrate and
test compounds to initiate the reaction. The RFU of the mixture at time 0 is recorded at
excitation wavelength 355 nm and emission wavelength 460 nm, after brief mixing on a
plate shaker. The reaction plate is covered with aluminum foil and kept in a dark
humidified oven at room temperature for 16 to 24 h. The RFU at the end of incubation is
recorded with the same excitation and emission settings used at time 0. The difference of
the RFU at time 0 and the end of incubation is representative of the activity of BACE1
under the compound treatment. RFU differences are plotted versus inhibitor
concentration and a curve is fitted with a four-parameter logistic equation to obtain the
IC50 values. (May, et al., Journal of Neuroscience, 3_1 , 16507- 16516 (20 11)).
The compounds of Examples 1-58 herein are tested essentially as described above
and exhibit an IC50 for BACE1 of lower than about 1 , with the compounds of
Examples 1, 2, 3, 34, and 57 exhibiting the following activity as shown in Table 5.
Table 5
Mean + SEM; SEM = standard error of the mean
This data demonstrates that the compounds of Examples 1 to 58 inhibit purified
recombinant BACE1 enzyme activity in vitro.
PDAPP Primary Neuronal Assay
A confirmatory whole cell assay is also run in primary neuronal cultures generated
from PDAPP transgenic embryonic mice (May, et al., Journal of Neuroscience, 3_ ,
16507-16516 (201 1)). Primary cortical neurons are prepared from Embryonic Day 16
PDAPP embryos and cultured in 96 well plates (15 x 104 cells/well in DMEM/F12 (1:1)
plus 10% FBS). After 2 days in vitro, culture media is replaced with serum free
DMEM/F12 (1:1) containing B27 supplement and 2 (final) of Ara-C (Sigma, C1768).
At day 5 in vitro, neurons are incubated at 37 °C for 24 h in the presence/absence of
inhibitors (diluted in DMSO) at the desired concentration. At the end of the incubation,
conditioned media are analyzed for evidence of beta-secretase activity, for example, by
analysis of Abeta peptides 1-40 and 1-42 by specific sandwich ELISAs. To measure these
specific isoforms of Abeta, monoclonal 2G3 is used as a capture antibody for Abeta 1-40,
and monoclonal 2IF12 as a capture antibody for Abeta 1-42. Both Abeta 1-40 and Abeta
1-42 ELISAs use biotinylated 3D6 as the reporting antibody (for description of
antibodies, see Johnson-Wood, et al., Proc. Natl. Acad. Sci. USA 94, 1550-1555 (1997)).
The concentration of Abeta released in the conditioned media following the compound
treatment corresponds to the activity of BACE1 under such conditions. The 10-point
inhibition curve is plotted and fitted with the four-parameter logistic equation to obtain
the IC50 values for the Abeta-lowering effect. The following exemplified compounds are
tested essentially as described above and exhibit the following activity for Abetalowering
effect:
Tab
Mean + SEM; SEM = standard error of the mean
This data demonstrates that the compounds of Table 6 inhibit Abeta production in
whole cells
In vivo Inhibition of Beta-Secretase
Several animal models, including mouse, guinea pig, dog, and monkey, may be
used to screen for inhibition of beta-secretase activity in vivo following compound
treatment. Animals used in this invention can be wild type, transgenic, or gene knockout
animals. For example, the PDAPP mouse model, prepared as described in Games et al.,
Nature 373, 523-527 (1995), and other non-transgenic or gene knockout animals are
useful to analyze in vivo inhibition of Abeta and sAPPbeta production in the presence of
inhibitory compounds. Generally, 2 month old PDAPP mice, gene knockout mice or nontransgenic
animals are administered compound formulated in vehicles, such as corn oil,
beta-cyclodextran, phosphate buffers, PHARMASOLVE®, or other suitable vehicles via
oral, subcutaneous, intra-venous, feeding or other route of administration. One to twentyfour
hours following the administration of compound, animals are sacrificed, and brains
are removed for analysis of Abeta 1-x. "Abeta 1-x" as used herein refers to the sum of
Abeta species that begin with residue 1 and end with a C-terminus greater than residue
28. This detects the majority of Abeta species and is often called "total Abeta". Total
Abeta peptides (Abeta 1-x) levels are measured by a sandwich ELISA, using monoclonal
266 as a capture antibody and biotinylated 3D6 as reporting antibody. {See May, et a ,
Journal of Neuroscience, 3_1 , 16507- 16516 (20 11)).
For acute studies, compound or appropriate vehicle is administered and animals
are sacrificed at about 3 hours after dosing. Brain tissue, is obtained from selected
animals and analyzed for the presence of Abeta 1-x. After chronic dosing brain tissues of
older APP transgenic animals may also be analyzed for the amount of beta-amyloid
plaques following compound treatment.
Animals (PDAPP or other APP transgenic or non-transgenic mice) administered
an inhibitory compound may demonstrate the reduction of Abeta in brain tissues, as
compared with vehicle-treated controls or time zero controls. For example, three hours
following a 30 mg/kg oral dose of the compound of Example 1 to young female PDAPP
mice, Abeta 1-x peptide levels are reduced approximately 37% in brain hippocampus, and
approximately 48% in brain cortex, p<0.01, compared to vehicle-treated mice. For
Example 2, a 10 mg/kg oral dose to young female PDAPP mice, Abeta 1-x peptide levels
are reduced approximately 40% in brain hippocampus and approximately 45% in brain
cortex, p<0.01, compared to vehicle-treated mice three hours after dosing. For a 30
mg/kg oral dose of Example 2 to young female PDAPP mice, Abeta 1-x peptide levels
are reduced approximately 52% in brain hippocampus, and approximately 54% in brain
cortex, p<0.01, compared to vehicle-treated mice three hours after dosing. For Example
3, a 10 mg/kg oral dose to young female PDAPP mice, Abeta 1-x peptide levels are
reduced approximately 34% in brain hippocampus and approximately 46% in brain
cortex, p<0.01, compared to vehicle-treated mice three hours after dosing. For Example
34, three hours following a 10 mg/kg oral dose of the compound of Example 34 to young
female PDAPP mice, Abeta 1-x peptide levels are reduced approximately 26%, p<0.05, in
brain hippocampus, and approximately 36% and 24 % in brain cortex for n=2 and p<0.01,
compared to vehicle-treated mice.
Given the activity of Examples 1, 2, 3, and 34 against the BACE enzyme in vitro,
these Abeta- lowering effects are consistent with BACE inhibition in vivo, and further
demonstrate CNS penetration of Examples 1, 2, 3, and 34.
These studies show that compounds of the present invention inhibit BACE and
are, therefore, useful in reducing Abeta levels.
WE CLAIM:
1. A compound of the formula:
Z is O or S;
R1 is H, F, CI, CN, OCH3, OCH2CH2OCH3,
R2 is H, F, CI, or CH3;
R3 is H, F, CI, CH3, CF3, C1-C3 alkoxy, OCH2CH2OCH3,
R4 is H, F, CI, or OCH3;
or a pharmaceutically acceptable salt thereof.
2. The compound or salt accordin to claim 1 in the (cis)-configuration:
The compound or salt according to either claim 1 or claim 2 wherein A
4. The compound or salt according to any one of claims 1 to 3 wherein A is:
The compound or salt according to any one of claims 1 to 4 wherein A is
The compound or salt according to any one of claims 1 to 5 wherein A is
The compound or salt according to any one of claims 1 to 4 wherein R3
8. The compound or salt according to any one of claims 1 to 4 and 7 wherein R3
is OCH3.
9. The compound or salt according to any one of claims 1 to 8 wherein Z is O.
10. The compound or salt according to any one of claims 1 to 8 wherein Z is S.
11. The compound or salt according to claim 1 which is N-[3-[(4aR,7aS)-2-
amino-4a-fluoro-5,7-dihydro-4H-furo[3,4-d][l,3]oxazin-7a-yl]-4-fluorophenyl]
-5-cyano-pyridine-2-carboxamide.
12. The compound according to claim 11 which is N-[3-[(4aR,7aS)-2-amino-4afluoro-
5,7-dihydro-4H-furo [3,4-d] [1,3]oxazin-7a-yl] -4-fluoro-phenyl]-5 -
cyano-pyridine-2-carboxamide.
13. A method of treating Alzheimer's disease in a patient, comprising
administering to a patient in need of such treatment an effective amount of a
compound of any one of claims 1-12, or a pharmaceutically acceptable salt
thereof.
14. A compound or pharmaceutically acceptable salt thereof according to any one
of claims 1-12 for use in therapy.
15. A compound or pharmaceutically acceptable salt thereof according to any one
of claims 1-12 for use in the treatment of Alzheimer's disease.
16. A pharmaceutical composition, comprising a compound or a pharmaceutically
acceptable salt thereof according to any one of claims 1-12 with one or more
pharmaceutically acceptable carriers, diluents, or excipients.