Description:FIELD OF THE INVENTION
[0001] The present disclosure generally relates to pharmaceutical organic compounds. Specifically, the present disclosure provides compounds of Formula (A), its stereoisomers, tautomers, pharmaceutically acceptable solvates or pharmaceutically acceptable salts thereof and pharmaceutical compositions comprising them. The present disclosure also provides a method for synthesizing the compounds of Formula (A), its stereoisomers, tautomers, pharmaceutically acceptable solvates or pharmaceutically acceptable salts thereof.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] The arthropod-borne dengue virus (DENV) is a life-threatening illness that is transmitted to humans by Aedes mosquitoes. DENV infections have rapidly increased with an estimated 390 million infections per year, of which 96 million manifest into clinical infections (S. Bhatt, P. W. Gething, O. J. Brady, J. P. Messina, A. W. Farlow, C. L. Moyes, J. M. Drake, J. S. Brownstein, A. G. Hoen and O. Sankoh, Nature, 2013, 496, 504). Over the past 50 years, DENV has seen widespread infections in over one hundred tropical and subtropical countries. For example, according to the World Health Organization (WHO), dramatic increases in dengue rates were reported in 2016 in countries like India (15,000 cases only in Delhi), Philippines (169,000 cases), Brazil (1.5 million cases), and Malaysia (111,000 cases)( W. H. Organization, World health statistics 2016: monitoring health for the SDGs sustainable development goals, World Health Organization, 2016). Different factors like climate change, migration, and unplanned rapid urbanization, have fashioned a perfect storm for dengue growth (C. P. Simmons, J. J. Farrar, N. van Vinh Chau and B. Wills, N. Engl. J. Med., 2012, 366, 1423–1432). Based on the WHO’s reports from the 2015-2016 period, half of the world’s population is now at risk of contracting dengue infection.
[0004] The first dengue vaccine Dengvaxia® was introduced in 2015 by Sanofi Pasteur (K. S. Vannice, A. Durbin and J. Hombach, Vaccine, 2016, 34, 2934–2938) and in endemic countries it has been employed to inoculate individuals between the ages of 9 to 45 years. Therapeutically there is no approved antiviral treatment for tackling fast-growing dengue outbreaks. Multiple cell-based and target-based approaches have been conducted by both academia and industry to identify DENV specific inhibitors with dissimilar mechanisms of action (L. Wang, Z. Feng, X. Wang, X. Wang and X. Zhang, Bioinformatics, 2009, 26, 136–138, and R. Zhou, I. Hotta, A. M. Denli, P. Hong, N. Perrimon and G. J. Hannon, Mol. Cell, 2008, 32, 592–599). Despite the improved rational approaches for developing novel anti-DENV drugs, no clinical candidates have emerged from those classes of molecules (S. Lim, J. Kwak, M. Kim and D. Lee, Nat. Commun., 2013, 4, 2641).
[0005] Thus, currently, there are no specific therapeutics available, and the only licensed vaccine encompasses risk of hospitalization in immunologically naive individuals. There is a need in the art to look for pharmaceutical compounds with anti-dengue activity.

OBJECTS OF THE INVENTION
[0006] An object of the present disclosure is to provide compounds for effective management of dengue and associated symptoms.
[0007] An object of the present disclosure is to provide compounds with enhanced inhibitory activity against the dengue virus type 2 (DENV2).
[0008] Another object of the present disclosure is to devise a method for synthesizing the compounds.

SUMMARY OF THE INVENTION
[0009] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0010] Aspects of the present disclosure provide 3-chlorobenzyl moiety linked diazaspiro[5.5]undecane compounds and a synthetic scheme for the compounds that have inhibitory activity against Dengue virus.
[0011] In an aspect, the present disclosure provides anti-dengue compounds of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof,

Formula (A)
wherein L may be selected from -CO- or -SO¬2-;
wherein R1 may be selected from -(C1-C6)alkyl, -(C3-C7)cycloalkyl, -CH2-(C3-C7)cycloalkyl, (C6-C14)aryl, -CH2-(C6-C14)aryl, (C5-C10)heterocyclyl, or -CH2-(C5-C10)heterocyclyl;
wherein R1 may be unsubstituted or substituted with halogen, -(C1-C6)alkyl, (C1-C6)alkoxy, -NH2, -NR2R3, -OH, cyano, nitro, -COOH, -OR2, -SO2, and -COOR2; and
wherein R2 and R3 may independently be selected from hydrogen or (C1-C6)alkyl.
[0012] In an embodiment, when L is -CO-, R1 may be selected from -(C1-C6)alkyl, -(C3-C7)cycloalkyl, or (C6-C14)aryl; wherein R1 may be unsubstituted or substituted with halogen, -(C1-C6)alkyl, or (C1-C6)alkoxy.
[0013] In an embodiment, when L is -SO2-, R1 may be selected from -(C1-C6)alkyl, -CH2-(C6-C14)aryl or -(C6-C14)aryl; wherein R1 may be unsubstituted or substituted with cyano, -(C1-C6)alkyl, or (C1-C6)alkoxy.
[0014] In an embodiment, the compound of Formula (A) may be selected from:
9-acetyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(cyclopropanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(cyclohexanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-benzoyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(2-fluorobenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(2-methylbenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-(4-bromobenzyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(4-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(3-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(4-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(methylsulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-tosyl-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
4-((1-(3-chlorobenzyl)-2-oxo-4-oxa-1,9-diazaspiro[5.5]undecan-9-yl)sulfonyl) benzonitrile;
1-(3-chlorobenzyl)-9-((4-methoxyphenyl)sulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-(benzylsulfonyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof.
[0015] In an aspect, the present disclosure provides a pharmaceutical composition comprising a compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof, and a pharmaceutically acceptable excipient.
[0016] In another aspect, the present disclosure provides a method of treating, alleviating or preventing dengue in a subject by administering a therapeutically effective amount of a compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof.
[0017] In yet another aspect, the present disclosure provides a method of synthesizing a compound of Formula (A), as shown in General Scheme I.


Formula A
Scheme I
wherein L and R1 are as defined earlier.
[0018] In an embodiment, the method comprises the steps of: (a) treating 4-amino-1-(tert-butoxycarbonyl) piperidine-4-carboxylic acid (I) with BH3-THF in THF to obtain compound (II); (b) reacting compound (II) with chloroacetyl chloride using Et3N to give a compound (III); (c) cyclizing compound (III) using potassium carbonate to give compound (IV); (d) treating compound (IV) with 3-chlorobenzyl bromide by using NaH to obtain compound (V); (e) deprotecting Boc from compound (V) by using a deprotecting agent to give a compound (VI); and (f) reacting the compound (VI) with R1-L-Cl to give compound of Formula (A).
[0019] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0021] Figure 1 provides the cytotoxicity (CC50) (Figures (a), (c) and (e)) and efficacy (EC50) (Figures (b), (d) and (f)) of compounds as per an embodiment of the present disclosure. Compounds SPO-6 (a,b), SPO-7 (c,d), and SPO-13 (e,f) were tested in Vero cells (Figures (a), (c) and (e)) and in DENV2-infected Vero cells (Figures (b), (d) and (f)), respectively. Data reports the mean ± standard error of the mean (SEM) of three independent experiments.

DETAILED DESCRIPTION OF THE INVENTION
[0022] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0023] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0024] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0025] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0026] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0027] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0028] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0029] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0030] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0031] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0032] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0033] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0034] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0035] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0036] The term "or", as used herein, is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.
[0037] The term, “(C1-C6)alkyl”, as used herein, refers to the radical of saturated aliphatic groups, including straight or branched-chain alkyl groups having six or fewer carbon atoms in its backbone, for instance, C1-C6 for straight chain and C3-C6 for branched chain. As used herein, (C1-C6)alkyl refers to an alkyl group having from 1 to 6 carbon atoms. Representative examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, 2-methylbutyl and 3-methylbutyl.
[0038] Furthermore, unless stated otherwise, the alkyl group can be unsubstituted or substituted with one or more substituents, for example, from one to four substituents, independently selected from the group consisting of halogen, hydroxy, cyano, nitro and amino. Examples of substituted alkyl include, but are not limited to hydroxymethyl, 2-chlorobutyl, trifluoromethyl and aminoethyl.
[0039] The term, “(C3-C7)cycloalkyl”, as used herein, refers to the radical of saturated cyclic groups having carbon atoms in its backbone. As used herein, (C3-C7)cycloalkyl refers to a cyclic alkyl group having from 3 to 7 carbon atoms. Representative examples of cycloalkyl include, but are not limited to, cyclohexyl, cyclopropyl, and cyclobutyl.
[0040] Furthermore, unless stated otherwise, the cycloalkyl group can be unsubstituted or substituted with one or more substituents, for example, from one to four substituents, independently selected from the group consisting of halogen, hydroxy, cyano, nitro and amino. Examples of substituted alkyl include, but are not limited to, methylcyclohexyl, chlorocycloheptyl, or ethylcycloheptyl.
[0041] The term,“(C1-C6)alkoxy" refers to a (C1-C6)alkyl having an oxygen radical attached thereto. Representative examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy and tert-butoxy. Furthermore, unless stated otherwise, the alkoxy groups can be unsubstituted or substituted with one or more groups. A substituted alkoxy refers to a (C1-C6)alkoxy substituted with one or more groups, particularly one to four groups independently selected from the groups indicated above as the substituents for the alkyl group.
[0042] The term "(C6-C14)aryl" or "aryl" as used herein refers to monocyclic, bicyclic, or tricyclic hydrocarbon groups having 6 to 14 ring carbon atoms, wherein at least one carbocyclic ring is having a p electron system. Examples of (C6-C14) aryl ring systems include, but are not limited to, phenyl and naphthyl.
[0043] The term, “(C5-C10)heterocyclyl”, as used herein refers to a 5- to 10-membered, saturated, partially unsaturated or unsaturated monocyclic or bicyclic ring system containing 1 to 4 heteroatoms independently selected from the group consisting of oxygen, nitrogen and sulfur. Saturated heterocyclic ring systems do not contain any double bond, whereas partially unsaturated heterocyclic ring systems contains at least one double bond, and unsaturated heterocyclic ring systems form an aromatic system containing heteroatom(s). The oxidized form of the ring nitrogen and sulfur atom contained in the heterocyclyl to provide the corresponding N-oxide, S-oxide or S,S-dioxide is also encompassed in the scope of the present disclosure. Representative examples of heterocyclyls include, but are not limited to, tetrahydrofuran, tetrahydrothiophene, pyrrolidine, dihydropyran, tetrahydropyran, thio-dihydropyran, thio-tetrahydropyran, piperidine, piperazine, morpholine, 1,3-oxazinane, 1,3-thiazinane, 4,5,6-tetrahydropyrimidine, 2,3-dihydrofuran, dihydrothiene, dihydropyridine, tetrahydropyridine, isoxazolidine, pyrazolidine, furan, pyrrole, thiophene, imidazole, oxazole, thiazole, triazole, tetrazole, benzofuran, indole, benzoxazole, benzothiazole, isoxazole, triazine, purine, pyridine, pyrazine, quinoline, isoquinoline, phenazine, oxadiazole, pteridine, pyridazine, quinazoline, pyrimidine, isothiazole, benzopyrazine and tetrazole.
[0044] The term, "halogen" as used herein refers to chlorine, fluorine, bromine or iodine atom.
[0045] The term, "therapeutically effective amount" as used herein refers to an amount of a compound of Formula A, a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof or a composition comprising a compound of Formula A, a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof, effective in producing the desired therapeutic response in a particular subject suffering from a disease or disorder.
[0046] The term, "subject" as used herein refers to an animal, preferably a mammal, and most preferably a human. The term "mammal" used herein refers to warm-blooded vertebrate animals of the class 'mammalia' , including humans, characterized by a covering of hair on the skin and, in the female, milk-producing mammary glands for nourishing the young, the term mammal includes animals such as cat, dog, rabbit, bear, fox, wolf, monkey, deer, mouse, pig and human.
[0047] The terms, “treatment", "treat" and "therapy" and the like as used herein refer to alleviate, slow the progression, attenuation, prophylaxis or as such treat the existing diseases or condition (e.g., dengue). Treatment also includes treating, preventing development of, or alleviating to some extent, one or more of the symptoms of the diseases or condition.
[0048] Aspects of the present disclosure provide 3-chlorobenzyl moiety linked diazaspiro[5.5]undecane compounds and a synthetic scheme for the compounds, wherein the compounds have inhibitory activity against Dengue virus.
[0049] In an embodiment, the present disclosure provides anti-dengue compounds of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof,

Formula (A)
wherein L may be selected from -CO- or -SO¬2-;
wherein R1 may be selected from -(C1-C6)alkyl, -(C3-C7)cycloalkyl, -CH2-(C3-C7)cycloalkyl, (C6-C14)aryl, -CH2-(C6-C14)aryl, (C5-C10)heterocyclyl, or -CH2-(C5-C10)heterocyclyl;
wherein R1 may be unsubstituted or substituted with halogen, -(C1-C6)alkyl, (C1-C6)alkoxy, -NH2, -NR2R3, -OH, cyano, nitro, -COOH, -OR2, -SO2, and -COOR2; and
wherein R2 and R3 may independently be selected from hydrogen or (C1-C6)alkyl.
[0050] In an embodiment, when L is -CO-; R1 may be selected from -(C1-C6)alkyl, -(C3-C7)cycloalkyl, or (C6-C14)aryl; wherein R1 may be unsubstituted or substituted with halogen, -(C1-C6)alkyl, or (C1-C6)alkoxy.
[0051] In a preferred embodiment, when L is -CO-; R1 may be selected from -methyl, cyclopropyl, cyclohexyl, or phenyl; wherein R1 may be unsubstituted or substituted with fluoro, bromo, chloro, methoxy or methyl.
[0052] In an embodiment, when L is -SO2-; R1 may be selected from -(C1-C6)alkyl, -CH2-(C6-C14)aryl or -(C6-C14)aryl; wherein R1 may be unsubstituted or substituted with cyano, -(C1-C6)alkyl, or (C1-C6)alkoxy.
[0053] In an embodiment, when L is -SO2-; R1 may be selected from methyl, phenyl, or benzyl; wherein R1 may be unsubstituted or substituted with cyano, methyl, -or methoxy.
[0054] In an embodiment, R1 may be selected from methyl, phenyl, benzyl, cyclopropyl, cyclohexyl, fluorophenyl, chlorophenyl, methoxyphenyl, bromophenyl, cyanophenyl, or methylphenyl.
[0055] In an embodiment, the compound of Formula (A) may be selected from:
9-acetyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(cyclopropanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(cyclohexanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-benzoyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(2-fluorobenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(2-methylbenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-(4-bromobenzyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(4-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(3-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(4-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(methylsulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-tosyl-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
4-((1-(3-chlorobenzyl)-2-oxo-4-oxa-1,9-diazaspiro[5.5]undecan-9-yl)sulfonyl) benzonitrile;
1-(3-chlorobenzyl)-9-((4-methoxyphenyl)sulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-(benzylsulfonyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof.
[0056] In an embodiment, the compound of Formula (A) can be converted into a pharmaceutically acceptable salt. The pharmaceutical acceptable salts of the compound of Formula (A) according to the disclosure are prepared in a manner known to one skilled in the art. Pharmaceutically acceptable salts of the compound of the present disclosure include but are not limited to, an acid salt of a compound of the present disclosure containing an amine or other basic group can be obtained by reacting the compound with a suitable organic or inorganic acid, resulting in pharmaceutically acceptable anionic salt forms. Examples of anionic salts include the acetate, benzenesulfonate, benzoate, bicarbonate, bitartrate, bromide, calcium edetate, camsylate, carbonate, chloride, citrate, dihydrochloride, edetate, edisylate, estolate, esylate, fumarate, glyceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate, hydrobromide, hydrochloride, hydroxynaphthoate, iodide, isethionate, lactate, lactobionate, malate, maleate, mandelate, mesylate, methylsulfate, mucate, napsylate, nitrate, pamoate, pantothenate, phosphate/diphosphate, polygalacturonate, salicylate, stearate, subacetate, succinate, sulfate, tannate, tartrate, teoclate, tosylate, and triethiodide salts.
[0057] In yet another embodiment, the pharmaceutically acceptable salts of the compound of the present disclosure containing acidic functional group can be prepared by reacting with a suitable base. Such a pharmaceutically acceptable salt may be made with a base which affords a pharmaceutically acceptable cation, which includes alkali metal salts (especially sodium and potassium), alkaline earth metal salts (especially calcium and magnesium), aluminum salts and ammonium salts, as well as salts made from physiologically acceptable organic bases such as trimethylamine, triethylamine, morpholine, pyridine, piperidine, picoline, dicyclohexylamine, N,N'-dibenzylethylenediamine, 2-hydroxyethylamine, bis-(2-hydroxyethyl)amine, tri-(2-hydroxyethyl)amine, procaine, dibenzylpiperidine, dehydroabietylamine, N,N'-bisdehydroabietylamine, glucamine, N-methylglucamine, collidine, quinine, quinoline, and basic amino acids such as lysine and arginine.
[0058] In an embodiment, the solvates include hydrates such as monohydrate, dihydrate, sesquihydrate, tetrahydrate, or combinations thereof. The terms tautomers and stereisomers have the meaning as well-defined in the art.
[0059] Compounds of the present disclosure have inhibitory activity against dengue virus type 2 (DENV2).
[0060] The compounds possess enhanced bioactivity and low cytotoxicity therefore can be formulated suitably for patients.
[0061] In an embodiment, the present disclosure provides a pharmaceutical composition comprising a compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof, and a pharmaceutically acceptable excipient.
[0062] In an embodiment, the excipient may be selected from diluent, carrier, binder, disintegrant, glidant, lubricant, coating material, filler, solvent, surfactants, solubilizers, emulsifier, preservatives, coloring agent, flavoring agent, or combinations thereof. However, a person of skill in the art would appreciate that any other excipient(s) may be employed without deviating from the spirit and scope of the disclosure.
[0063] In an embodiment, the pharmaceutical composition may be in the form of a tablet, pill, sachet, capsule, solution, suspensions, elixirs, cream, paste, gel, lotion, suspension, suppositories, emulsion, powder, nanoparticles, patches, aerosols, nasal sprays, microparticles, or nanoemulsion.
[0064] In an embodiment, the composition may be administered orally, bucally, intraperitonially, parenterally, intravenously, intramuscularly, subcutaneously, topically, transdermally, rectally, intramuscularly, or their combinations.
[0065] In an embodiment, the pharmaceutical compositions can be administered orally, for example in the form of pills, tablets, coated tablets, capsules, granules or elixirs. Administration, however, can also be carried out rectally, for example in the form of suppositories, or parenterally, for example intravenously, intramuscularly or subcutaneously, in the form of injectable sterile solutions or suspensions, or topically, for example in the form of ointments or creams or transdermally, in the form of patches, or in other ways, for example in the form of aerosols or nasal sprays.
[0066] For the production of oral dosages form of the compound of Formula (A) such as the pills, tablets, coated tablets and hard gelatin capsules, it is possible to use, for example, lactose, corn starch or compounds thereof, gum arabica, magnesia or glucose, etc. Pharmaceutically acceptable excipients that can be used for soft gelatin capsules and suppositories are, for example, fats, waxes, natural or hardened oils, etc. Suitable pharmaceutically acceptable excipients for the production of solutions, for example injection solutions, or of emulsions or syrups are, for example, water, physiological sodium chloride solution or alcohols, for example, ethanol, propanol or glycerol, sugar solutions, such as glucose solutions or mannitol solutions, or a mixture of the said solvents.
[0067] In an embodiment, the pharmaceutical compositions normally contain about 1% to 99%, for example, about 5% to 70%, or from about 10% to about 30% by weight of the compound of Formula (A) or its pharmaceutically acceptable salt. The amount of the compound of Formula (A) or its pharmaceutically acceptable salt in the pharmaceutical compositions normally is from about 5 to 500 mg or may be lower than or higher than the lower and the upper limit respectively.
[0068] The selected dosage level will depend upon a variety of factors including the activity of a compound of the present disclosure, or its salt employed, the route of administration, the time of administration, the rate of excretion of the particular compound being administered, the duration of the treatment, other concurrently administered drugs, compounds and/or materials, the age, sex, weight, condition, general health and prior medical history of the patient (subject) being treated, and other factors well known in medical arts. The dosage level may be determined by a physician.
[0069] In an embodiment, the present disclosure provides a compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof for use in management of dengue.
[0070] In an embodiment, the combination of compound of present disclosure with another therapeutic agent or treatment includes co-administration of a compound of Formula (A) with the other therapeutic agent or treatment as either a single combination dosage form or as multiple, separate dosage forms, administration of the compound of the present invention first, followed by the other therapeutic agent or treatment and administration of the other therapeutic agent or treatment first, followed by the compound of present disclosure. Further therapeutic agents are administered either simultaneously or sequentially.
[0071] In another embodiment of the present disclosure, the other therapeutic agent may be any agent that is known in the art to treat, prevent, or reduce the symptoms of a disease or disorder. The selection of other therapeutic agent(s) is based upon the particular disease or disorder being treated. Such choice is within the knowledge of a treating physician. Furthermore, the additional therapeutic agent may be any agent when administered in combination with the administration of a compound of the present disclosure provides benefit to the subject in need thereof.
[0072] In another embodiment, the present disclosure provides a method of treating, alleviating or preventing dengue in a subject by administering a therapeutically effective amount of a compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof.
[0073] In yet another aspect, the present disclosure provides a method of synthesizing a compound of Formula (A), as shown in General Scheme I.


Formula A
Scheme I
wherein L and R1 are as defined earlier.
[0074] In an embodiment, the method comprises the steps of: (a) treating 4-amino-1-(tert-butoxycarbonyl) piperidine-4-carboxylic acid (I) with BH3-THF in THF to obtain compound (II); (b) reacting compound (II) with chloroacetyl chloride using Et3N to give a compound (III); (c) cyclizing compound (III) using potassium carbonate to give compound (IV); (d) treating compound (IV) with 3-chlorobenzyl bromide by using NaH to obtain compound (V); (e) deprotecting Boc from compound (V) by using a deprotecting agent to give a compound (VI); and (f) reacting the compound (VI) with R1-L-Cl to give compound of Formula (A).
[0075] In an embodiment, deprotecting the Boc may be performed by acidic hydrolysis. In an embodiment, the deprotecting agent may be selected from an acid selected from hydrochloric acid, trifluoroacetic acid, 2,2,2-trifluoroethanol or trimethylsilyl chloride.
[0076] In some embodiments, the method provides high yield of compounds. In a preferred embodiment, the yields of compound (A) may be in the range of about 90% to about 95%.
[0077] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXAMPLES
[0078] The present disclosure is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the disclosure.
[0079] Material and methods: All chemicals were procured from Sigma-Aldrich (St Louis, MO, USA), Lancaster (Alfa Aesar, Johnson Matthey Co, Ward Hill, MA, USA), and Spectrochem Pvt. Ltd. (Mumbai, India). Silica gel-based TLC technique was used to monitor the reaction progress. Ethyl acetate (EtOAc) and pet ether mixture were used as the eluent and visualization on TLC were accomplished by UV light. Avance (300 MHz); Bruker, Fallanden, Switzerland instruments were used to record the 1H NMR spectra. Chemical shifts values were described in ppm downfield from internal TMS standard. On Micro mass, Quattro LC using ESI þ software with capillary electrical energy of 3.98 kV and ESI mode positive ion trap detector was used to record the ESI spectra. Melting points were calculated in open capillary tubes and results exposed were uncorrected. FT-IR spectrometer (Shimadzu FT-IR8300 spectrophotometer) was used to record the IR spectra and only major peaks are given in cm-1. All other reagents were available commercially with standard quality. All the prepared compounds were characterized by their spectral data (1H NMR, Mass, 13C NMR and IR) and physical nature. Elemental analyses of synthesized compounds were performed on a vario EL 111 CHN analyzer.
[0080] Example 1: Synthesis of compound of Formula (A)
[0081] The Scheme II below shows the method of synthesis of compounds of Formula (A). In the last step for synthesizing compounds of Formula (A), depending on what group ‘L’ is, i.e., -CO- or -SO2-, the compound (VI) is treated.

Scheme II
[0082] Preparation of t-Butyl 4-amino-4-(hydroxymethyl)piperidine)-1-carboxylate (II)
[0083] A clear solution of I (5.00 g, 20.4 mmol) in THF (50 mL) at 0°C was charged with 1.0 M borane tetrahydrofuran complex solution in THF (61.2 mL, 61.2 mmol) and stirred at room temperature for 16 h under N2 atmosphere. After completing the reaction, quenched with CH3OH (50 mL) and heated up to 75 °C. The reaction mixture was cooled to room temperature, concentrated under reduced pressure and azeotropes with CH3OH (50mL) to afford II (4.80 g, crude) as a colorless liquid (TLC Rf: 0.5 in 30% EtOAc in hexanes) and directly used as such in the next step without further purification. LC-MS (APCI + ESI) m/z: 231 [M + H]+.
[0084] Preparation of t-Butyl 4-(2-chloroacetamido)-4-(hydroxymethyl)piperidine-1-carboxylate (III)
[0085] A solution of II (4.00 g, 17.3 mmol) in THF (50 mL) at room temperature was added with Et3N (4.8 mL, 34.7 mmol), followed by the addition of chloro acetyl chloride (1.38 mL, 17.3 mmol) at 0 °C and stirred at room temperature for 3 h under N2 atmosphere. Upon reaction completion, the reaction mixture was quenched with H2O (20 mL) and extracted with EtOAc (2 × 20 mL). The combined organic layers were dried over anhydrous Na2SO4 and concentrated under reduced pressure to afford III (5.0 g, crude) as a colorless liquid (TLC Rf: 0.4 in 70% EtOAc in hexanes); LC-MS (APCI + ESI) m/z: 307 [(M+H]+.
[0086] Preparation of t-Butyl 2-oxo-4-oxa-1,9-diazaspiro[5.5]undecane-9-carboxylate (IV)
[0087] A clear solution of III (5.00 g, 16.3 mmol) in THF (50 mL) was charged with K2CO3 (4.49 g, 32.6 mmol) and continued stirring at room temperature for 16 h under N2 atmosphere. Upon reaction completion, the reaction mixture was quenched with H2O (20 mL) and extracted with EtOAc (2 × 20 mL). The combined organic layers were dried over anhydrous Na2SO4 and concentrated under reduced pressure to obtain crude products. The crude product was purified by column chromatography to obtain IV (3.5 g, 79%) as an off white solid (TLC Rf: 0.3 in 10% CH3OH in CH2Cl2). LC-MS (APCI + ESI) m/z:271 [M + H]+.
[0088] Preparation of t-Butyl 1-(3-chlorobenzyl)-2-oxo-4-oxa-1,9-diazaspiro[5.5]undecane-9-carboxylate (V):
[0089] A suspension of NaH (619 mg, 15.5 mmol) in THF (20 mL) was added with compound IV (3.50 g, 12.96 mmol) in THF (10 mL) dropwise at 0 °C and continued stirring for 15 min at 0 °C. 1-(bromomethyl)-3-chlorobenzene (2.0 mL, 15.5 mmol) was added and stirred at room temperature for 3 h. Upon reaction completion, the reaction mixture was quenched with H2O (20 mL) and extracted with EtOAc (2 × 20 mL). The organic layers were combined, dried over anhydrous Na2SO4, and concentrated under reduced pressure. The residue obtained was purified by combi flash column chromatography to afford V (4.00 g, 78%) as a white solid (TLC Rf: 0.4 in 80% EtOAc in n-hexanes). LC-MS (APCI + ESI) m/z:395 [M + H]+.
[0090] Preparation of 1-(3-Chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one hydrochloride (VI)
[0091] A suspension of V (4.00 g, 10.1 mmol) in 1,4-dioxane (40 mL) was charged with 4.0 M HCl in 1,4- dioxane (12.6 mL, 50.5 mmol) at 0°C and stirred at room temperature for 16 h. Upon reaction completion, the reaction mixture concentration was reduced to afford VI (3.00 g, 90%) as an off white solid (TLC Rf: 0.1 in 80% EtOAc in n-hexanes). LC-MS (APCI + ESI) m/z:295 [M + H]+.
[0092] Preparation of compound of Formula A
[0093] To a stirred solution of compound VI (0.303 mmol) in CH2Cl2 (10 mL) was added R1-SO2-Cl or R1-CO-Cl (0.454 mmol) at 0 °C, followed by Et3N (1.515 mmol) added and stirred at room temperature for 16 h. The reaction contents were quenched with water (10 mL), extracted with CH2Cl2 (2 × 10 mL). The organic layers were combined, dried over anhydrous Na2SO4, and concentrated under reduced pressure. The residue obtained was purified by combi flash column chromatography to afford the product.
[0094] Fifteen compounds were synthesized using the above method and have been named SPO-1 to SPO-15 for the purposes of the examples. Table 1 below provides the name, structure and characterization data of these compounds.
Table 1: Name, Structure and characterization of compounds
Compound Characterization data

9-acetyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-1) Yield:94%; White solid; mp:135-139 °C;
IR (KBr): ? (cm-1) 3080, 2927, 1642, 1600, 1326, 1158, 1075, 883, 542;
1H NMR (400 MHz, DMSO): ?? ppm 7.34–7.30 (m, 1H), 7.27–7.25 (m, 2H), 7.17–7.16 (m, 1H), 4.59 (s, 2H), 4.28–4.23 (m, 3H), 4.04 (s, 2H), 3.72–3.68 (m, 1H), 3.15-3.07 (m, 1H), 2.63–2.56 (m, 1H), 1.96 (s, 3H), 1.88-1.80 (m, 1H), 1.68-1.59 (m, 3H);
13CNMR (100 MHz, DMSO d6):?ppm???????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:391 [M + H]+; Anal. Calcd for C17H21ClN2O3: C, 60.62; H, 6.28; N, 8.32. Found: C, 60.58; H, 6.18; N, 8.29.

1-(3-chlorobenzyl)-9-(cyclopropanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-2) Yield: 92%; Off White solid; mp:145-149 °C;
IR (KBr): ? (cm-1) 2955, 1650, 1627, 1449, 1359, 1140, 980, 682, 480, 433;
1H NMR (400 MHz, CDCl3): ??? ppm 7.24–7.16 (m, 2H), 7.16 (s, 1H), 7.06 (d, J = 7.2 Hz, 1H), 4.62 (br s, 3H), 4.37 (s, 2H), 4.16–4.14 (m, 1H), 4.03–3.95 (m, 2H), 3.17 (br s, 1H), 2.61 (br s, 1H), 1.84–1.68 (m, 3H), 1.19–1.15 (m, 2H), 1.05–1.01 (m, 2H), 0.80-0.79 (m, 2H);
13CNMR(100MHz,DMSO-d6):??ppm??????? ?????? ?????? ?????? ?????? ?????? ?????? ?????? ?????? ????? ????, ????? ????? ????? ???? ???? ???;
LC-MS (APCI + ESI) m/z:363 [M + H]+; Anal. Calcd for C19H23ClN2O3 : C, 62.89; H, 6.39; N, 7.72. Found: C, 62.91; H, 6.42; N, 7.59.
1-(3-chlorobenzyl)-9-(cyclohexanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one(SPO-3) Yield: 94%; Off-White solid; mp:139-141 °C;
IR (KBr): ? (cm-1) 3005, 2362, 1745, 1642, 1458, 1326, 1158, 1112, 883, 514;
1H NMR (400 MHz, CDCl3): ?? ppm?7.26–7.23(m, 2H), 7.15 (s, 1H), 7.05 (d, J = 6.4 Hz, 1H), 4.60–4.57 (m, 3H), 4.36 (s, 2H), 4.05–3.83 (m, 3H), 3.10–3.05 (m, 1H), 2.56–2.40 (m, 2H), 1.69–1.66 (m, 2H), 1.53–1.45 (m, 3H), 1.15–1.26 (m, 5H), 0.88–0.83 (m, 2H);
13C NMR (100 MHz, DMSO-d6): ?? ppm ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:405 [M + H]+; Anal. Calcd for C22H29ClN2O3 : C, 65.25; H, 7.22; N, 6.92. Found: C, 65.34; H, 7.42; N, 6.90.
9-benzoyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-4) Yield: 93%; Off-White solid; mp:145-148 °C;
IR (KBr): ? (cm-1) 2958, 2362, 1627, 1416, 1188, 882, 682;
1H NMR (400 MHz, DMSO-d6): ?? ppm 7.44–7.40(m, 5H), 7.35–7.26 (m, 3H), 7.21–7.19 (m, 1H), 4.67 (s, 2H), 4.14 (br s, 1H), 4.23 (s, 2H), 4.06 (s, 2H), 3.39 (br s, 1H), 3.16 (br s, 1H), 2.89 (br s, 1H), 1.83 (br s, 2H), 1.66–1.53 (m, 2H);
13C NMR(100 MHz, DMSOd6): ??ppm??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:399 [M + H]; Anal. Calcd for C22H23ClN2O3: C, 66.24; H, 5.81; N, 7.02. Found: C, 66.14; H, 5.91; N, 6.99
1-(3-chlorobenzyl)-9-(2-fluorobenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-5) Yield: 95%; Off-White solid; mp: 130-132 °C;
IR (KBr): ? (cm-1) 3095, 2564, 1787, 1613, 1592, 1409, 1247, 1110, 1006, 741;
1H NMR (400 MHz, DMSO-d6): ?? ppm 7.48–7.47(m, 1H), 7.33–7.27 (m, 5H), 7.20–7.18 (m, 1H), 4.63 (br s, 2H), 4.44–4.41 (m, 1H), 4.23 (s, 2H), 4.12–4.06 (m, 2H), 3.22 (br s, 2H), 2.89 (t, J = 14.8 Hz, 1H), 1.85–1.71 (m, 3H), 1.52–1.49 (m, 1H);
13C NMR (100 MHz, DMSO-d6):??? ppm???????163.7, 158.7, 156.2, 141.9, 132.9, 131.3, 131.2, 130.0, 128.6, 126.4, 126.1, 125.0, 124.7, 124.1, 115.8, 115.6, 67.6, 67.5, 57.7, 42.5, 37.5, 30.9, 30.2; LC-MS (APCI + ESI):?m/z417 [M + H]+; Anal. Calcd for C22H22ClFN2O3 : C, 63.39; H, 5.32; N, 6.72. Found: C, 63.42; H, 5.42; N, 6.68.
1-(3-chlorobenzyl)-9-(2-methylbenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-6) Yield: 93%; Off-White solid; mp:145-149 °C;
IR (KBr): ? (cm-1) 2924, 2878, 1650, 1627, 1449, 1416, 1359, 1112, 980, 770;
1H NMR (400 MHz, DMSO-d6): ?? ppm 7.34–7.21(m, 7H), 4.67 (br s, 2H), 4.47–4.44 (m, 1H), 4.23 (s, 2H), 4.06 (s, 2H), 3.13–3.07 (m, 2H), 2.86 (t, J = 10.8 Hz, 1H), 2.23–1.14 (m, 3H), 1.87–1.85 (m, 1H), 1.68–1.42 (m, 3H);
13CNMR(100MHz,CDCl3): ??ppm????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:363 [M + H]+; Anal. Calcd for C23H25ClN2O3: C, 66.90; H, 6.10; N, 6.78. Found: C, 66.95; H, 6.14; N, 6.72.
9-(4-bromobenzyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-7) Yield: 94%; Yellow solid; mp:138-142 °C;
IR (KBr): ? (cm-1) 2927, 2886, 1665, 1625, 1430, 1272, 1110, 1007, 927, 840, 755;
1H NMR (400 MHz, CDCl3):?? ppm7.48 (d, J = 8.4 Hz, 2H), 7.19–7.10 (m, 5H), 7.01–7.00 (m, 2H), 4.56 (s, 2H), 4.29 (s, 2H), 3.92 (br s, 2H), 3.63–3.57 (m, 2H), 3.01–2.72 (m, 2H), 1.97–1.66 (m, 4H);
13C NMR(100 MHz, DMSo-d6): ?? ppm????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:477 [M + H]+; Anal. Calcd for C22H22BrClN2O3: C, 55.30; H, 4.64; N, 5.86. Found: C, 55.26; H, 5.90; N, 5.81.
1-(3-chlorobenzyl)-9-(4-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-8) Yield: 93%; White solid; mp:142-145 °C;
IR (KBr): ? (cm-1) 3095, 2880, 1927, 1787, 1722, 1647, 1613, 1434, 1409, 1284, 1247, 1085, 838, 741;
1H NMR (400 MHz, CDCl3):??? ppm 7.43–7.40 (m, 2H), 7.24–7.12 (m, 4H), 7.10–7.08 (m, 2H), 4.75 (d, J = 12 H, 1H), 4.63 (s, 2H), 4.36 (s, 2H), 3.98 (s, 2H), 3.49 (d, J = 12 Hz, 1H), 3.10 (br s, 1H), 2.79 (t, J = 12 Hz, 1H), 2.04–1.88 (m, 1H), 1.83–1.79 (m, 1H), 1.66–1.63 (m, 2H);
13C NMR (100 MHz, DMSOd6): ?? ppm????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:419 [M + H]+; Anal. Calcd for C22H22Cl2N2O3: C, 60.98; H, 5.12; N, 6.46. Found: C, 61.13; H, 5.08; N, 6.42.

1-(3-chlorobenzyl)-9-(3-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-9) Yield: 94%; Off-White solid; mp: 147-150 °C;
IR (KBr): ? (cm-1) 2927, 1658, 1624, 1466, 1288, 1110, 1036, 974, 750, 682;
1H NMR (400 MHz, DMSO-d6): ?? ppm7.35–7.25 (m, 4H), 7.21–7.19 (m, 1H), 6.99–6.93 (m, 3H), 4.68 (s, 2H), 4.39 (d, J = 14.4 Hz, 1H), 4.24 (s, 2H), 4.05 (d, J = 14.4 Hz, 2H), 3.75 (s, 3H), 3.41–3.38 (m, 1H), 3.13 (br s, 1H), 2.84 (t, J = 11.6 Hz, 1H), 1.88–1.66 (m, 3H), 1.49–1.46 (m, 1H);
13C NMR (100 MHz, DMSO-d6): ?? ppm???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z: 429 [M + H]+; Anal. Calcd for C23H25ClN2O4: C, 64.41; H, 5.88; N, 6.53. Found: C, 64.38; H, 5.91; N, 6.51.

1-(3-chlorobenzyl)-9-(4-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-10) Yield: 95%; Off-White solid; mp:134-138 °C;
IR (KBr): ? (cm-1) 2931, 2872, 1651, 1625, 1602, 1422, 1254, 1174, 763;
1H NMR (300 MHz, DMSO-d6): ? ppm7.33–7.21 (m, 4H), 7.19–7.17 (m, 1H), 6.97–6.92 (m, 3H), 4.66 (s, 2H), 4.32 (d, J = 14.4 Hz, 1H), 4.21 (s, 2H), 4.02 (d, J = 14.2 Hz, 2H), 3.74 (s, 3H), 3.39–3.36 (m, 1H), 3.09 (br s, 1H), 2.83 (t, J = 11.5 Hz, 1H), 1.84–1.66 (m, 3H), 1.47–1.44 (m, 1H);
13C NMR (100 MHz, DMSO-d6): ?? ppm?????????????????????????????????????????????????????????????; LC-MS (APCI + ESI) m/z: 429 [M + H]+; Anal. Calcd for C23H25ClN2O4: C, 64.41; H, 5.88; N, 6.53. Found: C, 64.45; H, 5.92; N, 6.55.
1-(3-chlorobenzyl)-9-(methylsulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-11) Yield: 90%; Off-White solid; mp: 142-145 °C;
IR (KBr): ? (cm-1) 2927, 2850, 1745, 1642, 8, 1418, 1347, 1326, 1158, 1112, 921, 771;
1H NMR (400 MHz, DMSO): ?? ppm 7.35–7.31 (m, 3H), 7.28–7.19 (m, 1H), 4.63 (s, 2H), 4.25 (s, 2H), 4.03 (s, 2H), 3.45–3.41 (m, 2H), 2.89–2.83 (m, 2H), 2.32 (s, 3H), 1.93–1.85 (m, 2H), 1.67–1.64 (m, 2H);
13CNMR(100MHz,DMSOd6): ? ppm?????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:372 [M + H]+; Anal. Calcd for C16H21ClN2O4S: C, 51.54; H, 5.68; N, 7.51. Found: C, 51.58; H, 5.64; N, 7.48.

1-(3-chlorobenzyl)-9-tosyl-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-12) Yield: 92%; Off-White solid; mp:147-150 °C;
IR (KBr): ? (cm-1) 3020, 2932, 2360, 1929, 1662, 1620, 1436, 1410, 1277, 1113, 981, 833, 757;
1H NMR (300 MHz, DMSO-d6): ?? ppm 7.69–7.67 (m, 2H), 7.54–7.48 (m, 2 H), 7.46–28 (m, 2H), 7.21 (s, 1H), 7.18–7.12 (m, 2H), 4.48 (s, 2H), 4.18 (s, 2H), 3.78 (s, 2H), 3.58 (d, J = 10.4 Hz, 2H), 2.48 (br s, 5H), 1.84–1.76 (m, 2H), 1.57–1.50 (m, 2H);
13C NMR (100 MHz, DMSO-d6): ?ppm 169.1, 167.7, 142.0, 139.0, 133.1, 132.9, 130.0, 129.2, 128.8, 128.5, 126.7, 126.4, 126.2, 125.0, 67.8, 67.6, 57.8, 42.6, 21.0, 20.8;
LC-MS (APCI + ESI) m/z:449 [M + H]+; Anal. Calcd for C22H25ClN2O4S : C, 58.85; H, 5.61; N, 6.24. Found: C, 58.78; H, 5.65; N, 6.19.
4-((1-(3-chlorobenzyl)-2-oxo-4-oxa-1,9-diazaspiro[5.5]undecan-9-yl)sulfonyl) benzonitrile (SPO-13) Yield: 94%; Off White solid; mp:155-160 °C;
IR (KBr): ? (cm-1) 3067, 2848, 1752, 1658, 1418, 1353, 1165, 916, 623;
1H NMR (400 MHz, DMSO-d6): ?? ppm?7.68-7.66 (m, 2H), 7.34-7.26 (m, 2 H), 7.20 (s, 1H), 7.14-7.11 (m, 3H), 4.47 (s, 2H), 4.18 (s, 2H), 3.78 (s, 2H), 3.58 (d, J=10.4 Hz, 2H), 2.45-2.41 (m, 2H), 1.84-1.76 (m, 2H), 1.60-1.57 (m, 2H);
13CNMR (100MHz, DMSO d6): ??ppm??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:460 [M + H]+; Anal. Calcd for C22H22ClN3O4S: C, 57.45; H, 4.82; N, 9.14. Found: C, 57.55; H, 4.79; N, 9.18.
1-(3-chlorobenzyl)-9-((4-methoxyphenyl)sulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-14) Yield: 95%; Off White solid; mp: 185-190 °C;
IR (KBr): ? (cm-1) 2854, 1653, 1642, 1598, 1348, 1157, 915, 728, 569;
1H NMR (400MHz, DMSO-d6): ? ppm7.68–7.66 (m, 2H), 7.34-7.26 (m, 2 H), 7.20 (s, 1H), 7.14-7.11 (m, 3H), 4.47 (s, 2H), 4.18 (s, 2H), 3.86 (s, 3H), 3.78 (s, 2H), 3.58 (d, J = 10.4 Hz, 2H), 2.45–2.41 (m, 2H), 1.84-1.76 (m, 2H), 1.60-1.57 (m, 2H);
13C NMR(100MHz, DMSO d6): ??ppm?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z:465 [M + H]+; Anal. Calcd for C22H25ClN2O5S: C, 56.83; H, 5.42; N, 6.02. Found: C, 56.79; H, 5.47; N, 5.98.
9-(benzylsulfonyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one (SPO-15) Yield: 95%; White solid; mp: 176-185 °C;
IR (KBr): ? (cm-1) 2927, 2853, 1750, 1648, 1417, 1347, 1113, 919, 698; 1H NMR (400 MHz, DMSO-d6): ? ppm?????-7.18 (m, 8H), 4.59 (d, J = 8.8 Hz, 2H), 4.39 (s, 1H), 4.23 (d, J = 11.6, 2H), 3.99 (d, J = 9.2 Hz, 2H), 3.46-3.44 (m, 2 H), 2.91-2.81 (m, 2H), 2.61-2.55 (m, 1H), 1.80-1.75 (m, 2H), 1.62-1.59 (m, 1H), 1.50-1.47 (m, 1H);
13C NMR (100 MHz, DMSO-d6): ?? ppm?????????????????????????????????????????????????
?????????????????????????????????????????????????????????????????????;
LC-MS (APCI + ESI) m/z: 485 [M + H]+; Anal. Calcd C22H25ClN2O4S: C, 58.85; H, 5.61; N, 6.24. Found: C, 58.76; H, 5.65; N, 6.28.

[0095] EXAMPLE 2: Antiviral efficacy of synthesized compounds
[0096] LLC/MK2 (ATCC® CCL-7) and Vero (ATCC® CCL-81) cells were sustained in M199 and MEM media, respectively, supplemented with fetal bovine serum and other reagents as previously described (S. Boonyasuppayakorn, A. Suroengrit, P. Srivarangkul, W. Yuttithamnon, S. Pankaew, T. Saelee, E. Prompetchara, S. Salakij and P. Bhattarakosol, J. Virol. Methods, 2016, 237, 25–31, and A. Suroengrit, W. Yuttithamnon, P. Srivarangkul, S. Pankaew, K. Kingkaew, W. Chavasiri and S. Boonyasuppayakorn, Sci. Rep., 2017, 7, 13696). A reference strain DENV2 (New Guinea C strain) was propagated in Vero cells as previously described. All compounds were primarily screened for the inhibitory effect against DENV2 (New Guinea C strain) and cytotoxicity. Compounds with viral inhibition and cell viability that exceeded 90 percent were selected for further investigation.
[0097] The compound efficacy against DENV2 infectivity was analyzed using 8-12 different concentrations of the selected compounds prepared in DMSO. The compound was added to DENV2-infected Vero cells (M.O.I of 0.1) and incubated for 3 days. Supernatants were collected for plaque titration and data were plotted and calculated to effective concentrations (EC50) from the non-linear regression analysis. The cytotoxic concentration of each compound was also analyzed using 8-12 different concentrations prepared in DMSO. Cells were incubated for 2 days before the addition of MTS reagent as previously described. Data were analyzed and cytotoxic concentration (CC50) was calculated from non-linear regression. Selectivity index (SI) was the ratio of CC50/EC50 representing the safety range of the particular compound.
[0098] From the primary screening, two compounds, SPO-6 and SPO-7, showed the strongest inhibitory effect at 10 µM against DENV2-infected cells at 92% and 97.7%, respectively. Compound SPO-13 showed moderate inhibition of 76% (refer Table 2).
Table 2: Primary screening result in DENV2-infected Vero cells at 10 µM concentration.
Compound % inhibition
SPO-3 59.22±0.022
SPO-5 47±0.042
SPO-6 92±0.003
SPO-7 97.7±0.005
SPO-8 59.9±0.019
SPO-9 67.85±0.011
SPO-10 71±0.016
SPO-11 20±0.022
SPO-12 87±0.010
SPO-13 76.82±0.450
SPO-14 82.85±0.003
SPO-15 95±0.482
Means and standard error of the means were calculated from
triplicate results

[0099] Further analysis, as in Table 3 and Figure 1, showed that SPO-6 with a 2-methyl substituent and SPO-7 with a bromo substituent was active against DENV2 with EC50 values of 11.43 ± 0.87 µM and 14.15 ± 0.50 µM, respectively. SPO-13 (4-cyano) was less active with an EC50 of 20.77 ± 1.92 µM. SPO-6 showed a strikingly mild cytotoxic effect with a CC50 of 155.53 ± 18.06 µM, while SPO-7 and SPO-13 were moderately toxic to Vero cells with CC50 values of 61.65 ± 2.55 µM and 90.46 ± 4.38 µM, respectively. Therefore, amongst the compounds of Table 1 SPO-6 was the most effective compound with the highest selectivity index (CC50/EC50) of 13.61.
Table 3: CC50 and EC50 of selected compounds.
Compound CC50 (µM) EC50 (µM) SI
SPO-6 155.53±18.06 11.43±0.87 13.61
SPO-7 61.65±2.55 14.15±0.50 4.36
SPO-13 90.46±4.38 20.77±1.92 4.36
Data represents mean ± standard error of the mean (SEM) of three independent experiments. SI = selectivity index (CC50/EC50)

[00100] Compound SPO-6 with 2-methylbenzoyl was found to be the most potent (Table 3), which may be correlated to the electron-donating effect of 2-methylbenzoyl group. In comparison, compounds SPO-7 (with a Br) and SPO-13 (with a CN) were also found to be active, potentially due to the polar hydrophobicity provided from the groups.
[00101] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

ADVANTAGES OF THE INVENTION
[00102] The present disclosure provides novel compounds that have inhibitory activity against dengue virus type 2 (DENV2).
[00103] The present disclosure also provides a method of synthesis of these anti-dengue compounds.

We Claims:

1. An anti-dengue compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof,

Formula (A)
wherein L is selected from -CO- or -SO¬2-;
wherein R1 is selected from -(C1-C6)alkyl, -(C3-C7)cycloalkyl, -CH2-(C3-C7)cycloalkyl, (C6-C14)aryl, -CH2-(C6-C14)aryl, (C5-C10)heterocyclyl, or -CH2-(C5-C10)heterocyclyl;
wherein R1 is unsubstituted or substituted with halogen, -(C1-C6)alkyl, (C1-C6)alkoxy, -NH2, -NR2R3, -OH, cyano, nitro, -COOH, -OR2, -SO2, and -COOR2; and
wherein R2 and R3 is independently selected from hydrogen or (C1-C6)alkyl.
2. The compound as claimed in claim 1, wherein L is -CO-; R1 is selected from -(C1-C6)alkyl, -(C3-C7)cycloalkyl, or (C6-C14)aryl; and wherein R1 is unsubstituted or substituted with halogen, -(C1-C6)alkyl, or (C1-C6)alkoxy.
3. The compound as claimed in claim 1, wherein L is -CO-; R1 is selected from -methyl, cyclopropyl, cyclohexyl, or phenyl; and wherein R1 is unsubstituted or substituted with fluoro, bromo, chloro, methoxy or methyl.
4. The compound as claimed in claim 1, wherein L is -SO2-; R1 is selected from -(C1-C6)alkyl, -CH2-(C6-C14)aryl or -(C6-C14)aryl; and wherein R1 is unsubstituted or substituted with cyano, -(C1-C6)alkyl, or (C1-C6)alkoxy.
5. The compound as claimed in claim 1, wherein L is -SO2-; R1 is selected from methyl, phenyl, or benzyl; and wherein R1 is unsubstituted or substituted with cyano, methyl, -or methoxy.
6. The compound as claimed in claim 1, wherein the compound of Formula (A) is selected from:
9-acetyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(cyclopropanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(cyclohexanecarbonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-benzoyl-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(2-fluorobenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(2-methylbenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-(4-bromobenzyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(4-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(3-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(4-methoxybenzoyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-(methylsulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
1-(3-chlorobenzyl)-9-tosyl-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
4-((1-(3-chlorobenzyl)-2-oxo-4-oxa-1,9-diazaspiro[5.5]undecan-9-yl)sulfonyl) benzonitrile;
1-(3-chlorobenzyl)-9-((4-methoxyphenyl)sulfonyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
9-(benzylsulfonyl)-1-(3-chlorobenzyl)-4-oxa-1,9-diazaspiro[5.5]undecan-2-one;
a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof.
7. A pharmaceutical composition comprising a compound of Formula (A), a stereoisomer, a tautomer, a pharmaceutically acceptable salt or a pharmaceutically acceptable solvate thereof, and a pharmaceutically acceptable excipient.
8. A method of synthesizing a compound of Formula (A), wherein the method comprises the steps of: (a) treating 4-amino-1-(tert-butoxycarbonyl) piperidine-4-carboxylic acid (I) with BH3-THF in THF to obtain compound (II); (b) reacting compound (II) with chloroacetyl chloride using Et3N to give a compound (III); (c) cyclizing compound (III) using potassium carbonate to give compound (IV); (d) treating compound (IV) with 3-chlorobenzyl bromide by using NaH to obtain compound (V); (e) deprotecting Boc from compound (V) by using a deprotecting agent to give a compound (VI); and (f) reacting the compound (VI) with R1-L-Cl to give compound of Formula (A).


Formula A