The present invention relates to a process for the preparation of phenyloxazolidinone derivatives. The compounds are useful antimicrobial agents, effective against a number of human and veterinary pathogens, including gram-positive aerobic bacteria such as multiply-resistant staphylococci, streptococci and enterococci as well as anaerobic organisms such as Bacterioides spp. and Clostridia spp. species, and acid fast organisms such as Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium spp.
This invention also relates to pharmaceutical composition containing the compounds of the present invention as potential antimicrobials.
Increasing antibacterial resistance in Gram-positive bacteria has presented a formidable treatment problem. The enterococci, although traditionally non-virulent pathogens, have been shown, when associated with Vancomycin resistance, to have an attributable mortality of approximately 40%. Staphylococcus aureus, the traditional pathogen of postoperative wounds has been resistant to Penicillin due to production of penicillinases. This resistance was overcome by the development of various penicillinase stable p lactams. But the pathogen responded by synthesizing modified target penicillin binding protein- 2' leading to less affinity for p lactam antibiotics and a phenotype known as Methicillin Resistant S. aureus (MRSA). These strains, till recently were susceptible to Vancomycin, which inspite of its various drawbacks, has become the drug of choice for MRSA infections. Streptococcus pneumoniae is a major pathogen causing pneumonia, sinusitis and meningitis. Until very recently it was highly susceptible to penicillin. Consequent upon acquiring a different PBP 2' strains with different susceptibility to penicillin have been reported from across the globe.
Oxazolidinones are a new class of synthetic antimicrobial agents, which kill gram-positive pathogens by inhibiting a very early stage of protein synthesis. The Oxazolidinones inhibit the formation of ribosomal initiation complex involving 30S and 50S ribosomes leading to prevention of initiation complex formation. Consequent to their novel mechanism of action, these compounds would be active against pathogens resistant to other clinically useful antibiotics.
The objectives of this invention was to synthesize, identify and profile oxazolidinone molecules which have good activity against multiply resistant gram positive pathogens like MRSA, VRE and PRSP. Some of these molecules have activity against MDR-TB and MAI strains, while others have significant activity against important anaerobic bacteria.
The compounds of the present invention are related by their substituted phenyl oxazolidinone ring structure in the compounds disclosed to the publications below except that the subject compounds have a diazine moiety attached to the phenyloxazolidinone which is further substituted by heterocyclic, aryl, substituted aryl, heteroaroamatic ring therefore the compounds are unique and have superior antibacterial activity.
W093/23384 application discloses phenyloxazolidinones containing a substituted diazine moiety and their uses as antimicrobials.
WO93/09103 application discloses substituted aryl and heteroaryl- phenyl-oxazolidinones useful as antibacterial agents
WO90/02744 application discloses 5-indolinyl-5P-amidomethyloxazolidinones, 3-(fused ring substituted) phenyl-5p-amidomethyl oxazolidinones which are useful as antibacterial agents.
European Patent Publication 352,781 discloses phenyl and pyridyl substituted phenyl oxazolidinones.
European Patent Application 312,000 discloses phenylmethyl and pyridinylmethyl substituted phenyl oxazolidinones.
U.S. Pat No. 5,254,577 discloses nitrogen heteroaromatic rings attached to phenyloxazolidinone .
U.S. Pat No. 5,547,950 and 5,700,799 also disclose the phenyl piperazinyl oxazolidinones.
Other references disclosing various phenyloxazolidinones include U.S. Pat. Nos. 4,801,600, 4,921,869, Gregory W.A., et. al., J.Med.chem., 32, 1673-81 (1989); Gregory W.A., et al.,
J.Med.Chem., 33, 2569-78 (1990); Wang C, et. al. Tetrahedron, 45, 1323-26 (1989); and Brittelli, etl. al, J.Med. Chem, 35, 1156 (1992) and Bioorganic and Medicinal Chemistry Letters, 9, p 2679-2684, 1999.
An object of the present invention is to provide processes for the novel phenyloxazolidinones derivatives that exhibit significantly greater antibacterial activity, than available with the present compounds against multiply resistant gram positive pathogens like MRSA, VRE and PRSP against MDR-TB and MAI strains, in order to provide safe and effective treatment of bacterial infections.
In order to achieve the above-mentioned objectives and in accordance with the purpose of the invention as embodied and broadly described herein, there is provided a process for the preparation of phenyloxazolidinone derivatives represented by the Formula XII, as shown in the accompanied drawings wherein
(Formula Removed)
The most preferred compounds in this series would be prepared as the optically pure enantiomers having the (S)-configuration according to the Cahn-Ingold-Prelog notation at C5 of the oxazolidinone ring. Athough, the (S)-enantiomer of this series of compounds is preferred since the (S)-enantiomer has two times antibacterial than the corresponding compound racemic is active. When a chiral center exists in any of the substituents bonded to phenyl oxazolidinone the diastereomers are possible. The scope of the individual isomers and mixture of enantiomers of the structural Formula XII also included.
The compounds of the present invention are useful as antimicrobial agents, effective against a number of human and veterinary pathogens, particularly aerobic Gram-positive bacteria, including multiply-antibiotic resistant staphylococci and streptococci, as well as anaerobic organisms such as Mycobacterium tuberculosis and other mycobacterium species.
For preparing pharmaceutical compositions from the compounds described by this invention, inert, pharmaceutically acceptable carriers can be either solid or liquid. Solid form preparations
include powders, tablets, dispersible granules, capsules, cachets, suppositories, and ointments. A solid carrier can be one or more substances which may also act as diluents, flavouring agents, solubilizers, lubricants, suspending agents, binders, or tablets disintegrating agents; it can also be as finely divided solid which is in admixture with the finely divided active compound. For the preparation of tablets, the active compound is mixed with carrier having the necessary binding properties in suitable proportions and compacted in the shape and size desired. The powders and tablets preferably contain from about 5 to about 70 percent of the active ingredient. Suitable solid carriers are lactose, pectin, dextrin, starch, gelatin, tragacanth, low melting wax, cocoa butter, and the like. The term "preparation" is intended to include the formulation of the active compound with encapsulating material as carrier providing a capsule in which the active component (with or without other carriers) is surrounded by carrier, which is thus in association with it. Similarly, capsules can be used as solid dosage forms suitable for oral administration.
Liquid form preparations include solutions, suspensions, and emulsions. As an example may be mentioned water or water-propylene glycol solutions for parenteral injection. Such solutions are prepared so as to be acceptable to biological systems (isotonicity, pH, etc.). Liquid preparations can also be formulated in solution in aqueous polyethylene glycol solution. Aqueous solutions suitable for oral use can be prepared by dissolving the active component in water and adding suitable colorants, flavours, stabilizing, and thickening agents as desired. Aqueous suspension suitable for oral use can be made by dispersing the finely divided active component in water with viscous material, i.e., natural or synthetic gums, resins, methylcellulose, sodium carboxymethyl cellulose, and other well-known suspending agents.
Ointment preparations contain heavy metal salts of a compound of Formula XII with a physiologically acceptable carrier. The carrier is desirably a conventional water-dispersible hydrophilic or oil-in-water carrier, particularly a conventional semi-soft or cream-like water-dispersible or water soluble, oil-in-water emulsion infected surface with a minimum of discomfort. Suitable compositions may be prepared by merely incorporating or homogeneously admixing finely divided compounds with the hydrophilic carrier or base or ointment.
Preferably, the pharmaceutical preparation is in unit dosage form. In such form, the preparation is subdivided into unit doses containing appropriate quantities of the active component. The unit dosage form can be a packaged preparation, the package containing discrete capsules, powders in
vials or ampoules, and ointments capsule, cachet, tablet, gel, or cream itself or it can be the appropriate number of any of these packaged forms.
The quantity of active compound in a unit dose of preparation may be varied or adjusted from less than 1 mg to 100 mg according to the particular application and the potency of the active ingredient.
In therapeutic use as agents for treating bacterial infections the compounds utilized in the pharmaceutical method of this invention are administered at the initial dosage of about 3 mg to about 40 mg per kilogram daily. The dosages, however, may be varied depending upon the requirements of the patient and the compound being employed. Determination of the proper dosage for a particular situation is within the smaller dosages, which are less than the optimum dose. Small increments until the optimum effect under the daily dosage may be divided and administered in portions during the day if desired.
In order to achieve the above mentioned objects in accordance with the purpose of the invention as embodied and broadly described herein, there is provided process for the preparation of compounds of Formula XII as shown in Scheme-IIIB of the accompanied drawings. Phamiaceutically acceptable non-toxic acid addition salts of the compounds of the present invention of Formula XII as shown in the accompanied drawings may be formed with inorganic or organic acids, by methods well known in the art.
The present invention also includes within its scope prodrugs of the compounds of Formula XII. In general, such prodrugs will be functional derivatives of these compounds, which readily get converted in vivo into defined compounds. Conventional procedures for the selection and preparation of suitable prodrugs are known.
The invention also includes phamiaceutically acceptable salts, the enantiomers, diastereomers, N-oxides, prodrugs, metabolites in combination with phamiaceutically acceptable carrier and optionally included excipient.
Other objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention. The objects and the advantages of the invention may be released and obtained by means of the mechanism and combination pointed out in the appended claims.
SCHEME- IIIB
The compounds of Formula XII can be prepared by following the reaction sequences depicted in
Scheme-IIIB, as shown in the accompanied drawings, which method comprises reacting a
compound of Formula IX with hydroxylamine hydrochloride, hydrazine hydrate or 1,3-propane
diol in a solvent such as pyridine or ethanol to give phenyloxazolidinone derivatives of Formula
XII (wherein R17
(Formula Removed)
which (when Rn is\ =ZN-OH ) on reaction
(Formula Removed)
with isocyanate or triflic anhydride in the presence of a base such as triethylamine in a solvent
such as dichloromethane gives phenyloxazolidinone derivatives of Formula XII (wherein R17 is
(Formula Removed)
The transformations effected are described in the experimental section. In the above synthetic
methods where specific bases, solvents, etc. are mentioned, it is to be understood that the other
bases, solvents etc. may be used. Similarly, the reduction temperature and duration of the
reaction may be adjusted according to the need. An illustrative list of particular compounds
according to the invention and capable of being produced by the above mentioned schemes
include:
Compound No. Chemical Name
60. (S)-N-[[3-[3-Fluoro-4-[N-l-[4-(2-furyl-(5-aldoxime)methyl}] piperazinyl] phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide
61. (S)-N-[[3-[3-Fluoro-4-[N-l[4-{2-furyl(5-aldoxime(methyl-4-(N-carboxyaminophenyl acetate) methyl}]piperazinyl]phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide
62. (S)-N-[[3-[3-Fluoro-4[N-l-[4-{2-furyl-(5-hydrazone)-methyl}]-piperazinyl]-phenyl]-2-oxo-5-oxazolidinyl]-methyl]acetamide
64. (S)-N-[[3-[3-Fluoro-4-[N-l[4-{2-furyl(5-cyano)methyl}] piperazinyljphenyl] -2-oxo-5-oxazolidinyl]methyl]acetamide
66. (S)-N-[[3-Fluoro-4-[N-l[5-(l,3-dioxane)-2-furylmethyl]piperazinyl]phenyl]-2-oxo-5-oxazolidinyl]methyl] acetamide

Pharmacological Testing
The compounds of the invention display antibacterial activity when tested by the agar incorporation method. The following minimum inhibitory concentrations (µg/ml) were obtained for representative compounds of the invention, which are given below in Table I.
TABLE 1
MIC of compounds and standard antibiotics against important pathogens

(Table Removed)
The in vitro antibacterial activity of the compounds were demonstrated by the agar incorporation method (NCCLS M 7 and M 100-S8 documents). Briefly, the compounds were dissolved in DMSO and doubling dilution of the compounds were incorporated into Meuller Hilton agar before solidification. Inoculum was prepared by suspending 4 to 5 colonies into 5 ml of normal saline solution and adjusting the turbility to 0.5 Macfarland turbidity standard tables (1.5 x 10^ CFU/ml), after appropriate dilutions, 10^ CFU/spot was transfered into the surface of dried plate and incubated for 18 hours (24 hours for MRSN studies). The concentration showing no growth of the inoculated culture was recorded as the MIC. Appropriate ATCC standard strains were simultaneously tested and result recorded only when the MIC's against standard antibiotics were within the acceptable range.
ABERIVATIONS:
1) S.aureus ATCC 25923 Staphylococus aureus ATCC 25923
2) MRSA 15187 -Methicillin Resistant Staphylococcus aureus
3) Ent.faecalis ATCC 29212 —Enterococcus faecalis ATCC 29212
4) Ent. faecium 6A ~ Enterococcus faecium 6A Vanr, Cipro r
5) Strep, pne. ATCC 6303 —Streptococcus pneumoniae ATCC 6303
6) Strep.pyog. ATCC 19615 Streptococcus pyogenes
7) S. epidermidis - Staphylococcus epidermidis ATCC 12228
The examples mentioned below demonstrate the general synthetic procedure as well as the specific preparation for the preparation for the preferred compound. The examples are given to illustrate the details of the invention and should not be constrained to limit the scope of the present invention.
Most of the compounds were characterized using NMR, IR and were purified by chromatography. Crude products were subjected to column chromatography purification using silica gel (100-200 or 60-120 mesh) as secondary phase.
EXAMPLE
Preparation of (S)-N-[[3-[3-Fluoro-4-[N-l-[4-(2-furyI-(5-aldoxime)methyl}]
piperazinyl] phenyl] -2-oxo-5-oxazolidinyl] methyl] acetamide (Compound No. 60)
To a solution of (S)-N-[[3-[3-Fluoro-4-[N-l-[4-(2-furyl-(5-formyl)methyl}] piperazinyl] phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide (140 mg 0.31 mmol) in dry pyridine was added hydroxylamine hydrochloride (26 mg, 0.38 mmol). The whole reaction mixture
was stirred at 25°C for about 4 hours. TLC of the reaction mixture was monitored. A slower moving spot was observed compare to starting compound. Pyridine was removed under reduced pressure and traces of pyridine were removed with toluene to yield title compound of 140 mg.
1HNMR(DMSO-d6);8.70(d,2H),8.08-8.03(m,lH),7.65-7.61(m,lH),7.78(d,lH),7.24 7.1 l(m,2H),4.70(d,lH),4.49(s,2H),4.07(t,lH),1.82(s,3H), 3.72 (m, 2H), 3.53-2.88 (m, 9H).
EXAMPLE
Preparation of (S)-N-[[3-[3-Fluoro-4-[N-l [4-{2-furyl(5-cyano)methyl}]
piperazinyl] phenyl] -2-oxo-5-oxazolidinyl] methyl] acetamide (Compound No. 64)
(S)-N- [ [3 -[3 -Fluoro-4- [N-1 [4- {2-furyl(5 -aldoxime)methyl} ]piperazinyl] phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide (6126, 3.5g,0.76 mmol) was taken in dichloromethane (5 mL) and triethylamine(1.5g, 1.5 mmol) was added and the reaction mixture was maintained at -78°C. Triflic anhydride (4.3g, 1.5 mmol) in dichloromethane (2 mL) was added dropwise after complete addition, the temperature of the reaction mixture was allowed to rise to room temperature in 2 hours. The reaction mixture was concentrated
under vacuum, water (10 mL) was added and extracted with dichloromethane (3x10 mL). The combined organic layer was dried over anhydrous sodium sulphate, filtered and concentrated to obtain the title compound.
NMR(CDCB); 7.44-6.10(m, 6H), 4.74(m,lH), 4.00(t, 2H), 3.73-3.62(m,5H), 3.09-2.68(m, 8H,), 2.01(s,3H)
(S)-N-[[3-[3-Fluoro-4-[N-l[4-{2-furyl(5-aldoxime(methyl-4-(N-carboxyamino phenylacetate) methyl} ] piperazinyl] phenyl] -2-oxo-5-oxazolidinyl] methyl] acetamide (Compound No. 61)
The title compound was prepared by using the procedure.
EXAMPLE
Preparation of (S)-N-[[3-[3-Fluoro-4[N-l-[4-{2-furyl-(5-hydrazone)-methyl}]-piperazinyl]-phenyl]-2-oxo-5-oxazolidinyl]-methyl]acetamide (Compound No. 62)
To a solution of (S)-N-[[3-[3-Fluoro-4-[N-l-[4-(2-furyl-(5-formyl)methyl}] piperazinyl] phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide (140 mg, 0.31 mmol) in ethanol (4.0 ml) was added hydrazine hydrate (100mg) and catalytic amount of concentrated sulfuric acid.
The whole reaction mixture was stirred at 25°C for 48 hours. TLC of the reaction mixture showed no changes. Stirring was continued for another 12 hours, no change in TLC was observed. Solvent was evaporated to dryness and the solid residue was digested
with ether to give 100 mg of title compound of m.p. 78-181°C.
1HNMR(CDC13): 8=7.6 1(S,1H),7.42 (dd,lH),7.04 (t,lH), 6.92(t,lH), 6.44(d,lH), 6.28 (bs,2H), 5.60 (bs,2H), 4.77 (bs,lH), 4.02 (t,lH), 3.77-3.61(m,8H), 3.10 (bs,lH), 2.71(bs,lH),2.02(s,3H).
EXAMPLE
Preparation of (S)-N-[[3-Fluoro-4-[N-l[5-(l,3-dioxane)-2-
furylmethyl] piperazinyl] phenyl]-2-oxo-5-oxazolidinyl] methyl] acetamide
(Compound No. 66)
The title compound was made using (S)-N-[[3-Fluoro-4-[N-l[4-{2-furyl(5-formyl)methyl}]piperazinyl]phenyl]-2-oxo-5-oxazolidinyl]methyl] acetamide with 1,3-propane diol and boron trifluoride etherate using standard literature procedures.

WE CLAIM:
1. A process for the preparation of phenyloxazolidinone derivative of Formula XII as
shown in Scheme IIIB of the accompanied drawings and its pharmaceutically acceptable
salts, enantiomers, diastereomers, N-oxides, prodrugs or metabolites, wherein
(Formula Removed)
which method comprises reacting a compound of Formula IX with hydroxylamine
hydrochloride, hydrazine hydrate or 1,3-propane diol in a solvent such as pyridine or
ethanol to give phenyloxazolidinone derivatives of Formula XII (wherein R17 is
(Formula Removed)
which (when R17 is
(Formula Removed)
on reaction with isocyanate or
(Formula Removed)
triflic anhydride in the presence of a base such as triethylamine in a solvent such as
dichloromethane gives phenyloxazolidinone derivatives of Formula XII (wherein R17 is
(Formula Removed)
2. The process according to claim 1 wherein phenyloxazolidinone derivatives are namely,
63.(S)-N-[[3-[3-Fluoro-4-[N-l-[4-(2-furyl-(5-aldoxime)methyl}]piperazinyl] phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide,
64. (S)-N-[[3-[3-Fluoro-4-[N-l[4-{2-furyl(5-aldoxime(methyl-4-(N-
carboxyaminophenyl acetate) methyl}]piperazinyl]phenyl]-2-oxo-5-
oxazolidinyl]methyl]acetamide,
65.(S)-N-[[3-[3-Fluoro-4[N-l-[4-{2-furyl-(5-hydrazone)-methyl}]-piperazinyl]-phenyl]-2-oxo-5-oxazolidinyl]-methyl]acetamide,
65. (S)-N-[[3-[3-Fluoro-4-[N-l[4-{2-furyl(5-cyano)methyl}] piperazinyljphenyl] -2-
oxo-5-oxazolidinyl]methyl]acetamide and
67. (S)-N-[[3-Fluoro-4-[N-l[5-(l,3-dioxane)-2-furylmethyl]piperazinyl]phenyl]-2-oxo-5-oxazolidinyl]methyl] acetamide.
3. A process for the preparation of pharmaceutical composition comprising the compound
of claim 1 and a pharmaceutically acceptable carrier.
4. The process for the preparation of phenyloxazoHdinone derivatives of Formula XII, substantially as herein described and illustrated by examples herein.