WO2006018682A2

WO2006018682A2 - Oxazolidinone derivatives as antimicrobials

Info

Publication number: WO2006018682A2
Application number: PCT/IB2005/002226
Authority: WO
Inventors: Biswajit Das; Shahadat Ahmed; Ajay Singh Yadav; Soma Ghosh; Ashok Rattan
Original assignee: Ranbaxy Laboratories Limited
Priority date: 2004-08-11
Filing date: 2005-07-27
Publication date: 2006-02-23
Also published as: WO2006018682A3

Abstract

The present invention relates to certain substituted phenyl oxazolidinones and to process for the synthesis of the same. This invention also relates to pharmaceutical compositions containing the compounds of the present invention as antimicrobials. The compounds are useful antimicrobial agents, effective against a number of human and veterinary pathogens, including gram-positive aerobic bacteria such as multiple-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.

Description

OXAZOLIDINONE DERIVATIVES AS ANTIMICROBIALS

Field of the Invention

The present invention relates to certain substituted phenyl oxazolidinones and to processes for the synthesis of the same. This invention also relates to pharmaceutical compositions containing the compounds of the present invention as antimicrobials. The compounds are useful antimicrobial agents, effective against a number of human and veterinary pathogens, including gram-positive aerobic bacteria such as multiple-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.

Background of the Invention

Increasing antibacterial resistance in Gram-positive bacteria has presented a formidable treatment problem. The enterococci, although traditionally not 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 β lactams. But the pathogen responded by synthesizing modified target penicillin binding protein- 2' leading to less affinity for β 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. Recently though, 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. Oxazolidinones inhibit the formation of ribosomal initiation complex involving 3OS and 5OS ribosomes leading to prevention of initiation complex formation. These compounds are active against pathogens resistant to other clinically useful antibiotics. WO 04/14392 discloses substituted phenyl oxazolidinone derivatives which are described as antimicrobials. WO 03/97059 discloses polymorphic forms of phenyl oxazolidinone derivatives. WO 03/08389 discloses substituted phenyl oxazolidinone derivatives described as potential antimicrobials. WO 03/07870 discloses oxazolidinone derivatives which are described as antimicrobials. WO 04/14392 discloses substituted phenyl oxazolidinone derivatives which are described as antimicrobials. WO 93/09103 discloses substituted aryl and heteroaryl phenyl oxazolidinone said to be useful as antibacterial agents. WO 98/54161 and US 6255304 disclose oxazolidinone antibacterial agents having a thiocarbonyl functionality.

WO 00/29396 discloses substituted phenyloxazolidione derivatives for producing antibacterial medicament for treating human being and animals. WO 01/80841 discloses use of thioamide oxazolidinones allegedly useful for the treatment of bone resorption and osteoporosis. WO 01/94342 and US6, 689,779 disclose oxazolidinone derivatives having pyridine or pyrimidine moieties and a process for the preparation thereof. WO 03/022824 discloses oxazolidione and/or isoxazoline described as antibacterial agents. WO

03/072553 discloses N-aryl-2-oxazolidinone-5-carboxamides and their derivatives and their use as antibacterial agents. WO 03/006447 discloses oxazolidione compounds having thiocarbonyl functionality which are described as antibacterial agents.

US 5,565,571, US 5,801,246, US 5,756,732, US 5,654,435, US 5,654,428 disclose substituted aryl and heteroaryl phenyloxazolidinones which are described as antibacterial agents.

Summary Of The Invention

Oxazolidinone derivatives which have a good activity against multiple resistant gram positive pathogens like methicilline resistant Staphylococcus aureus (MRSA), Vancomycin- resistant Enterococci (VRE) and Streptococcus pneumonia are disclosed.

Some of these molecules have activity against multiple drug resistant tuberculosis (MDR- TB) strain, while others have significant activity against important anaerobic bacteria.

Phenyloxazolidinone derivatives exhibiting good antibacterial activity against Gram-positive pathogens like MRSA, VRE and PRSP against MDR-TB and MAI strains and Gram-negative pathogens like morazella catarrhalis and Haemophilus influenza in order to provide safe and effective treatment of bacterial infection are provided.

Processes for the synthesis of phenyloxazolidinones derivative represented by Formula I are also provided,

as well as their pharmaceutically acceptable salts, pharmaceutically acceptable solvates, esters, enantiomers, diastereomers, N-oxides, polymorphs, prodrugs or metabolites, wherein

V can be hydrogen or fluorine; and A can be

with the provisio that when A is pyridinyl then V is fluorine.

Compounds disclosed herein can be useful antimicrobial agents, effective against a number of human and veterinary pathogens, particularly aerobic and Gram-positive bacteria, including multiply-antibiotic resistant Staphylococci and Streptococci, as well as anaerobic organisms such as Mycobacterium tuberculosis and other Mycobacterium species.

Pharmaceutical compositions comprising the compounds disclosed herein, their enantiomers, diastereomers, polymorphs, pharmaceutically acceptable salts, pharmaceutically acceptable solvates, N-oxides or metabolites in combination with pharmaceutically acceptable carriers and optionally included excipients are also provided herein.

For preparing pharmaceutical compositions from the compounds described herein, 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, flavoring 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, flavors, 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, methyl cellulose, sodium carboxymethyl cellulose and other well-known suspending agents.

Ointment preparations contain heavy metal salts of a compound of Formula I 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.

The pharmaceutical preparation can be in unit dosage form. In such forms, 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 several grams 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 another aspect, processes for the synthesis of compounds of Formula I are provided. Pharmaceutically acceptable acid addition salts of the compounds of Formula I may be formed with inorganic or organic acids, by methods well known in the art.

Prodrugs of the compounds of Formula I are also included. 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 to the artisan of ordinary skill in the art.

Other 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. Detailed Description of the Invention

The compounds described herein are represented by general Formula I, and may be prepared by techniques well known in the art and familiar to the skilled synthetic organic chemist. In addition, the compounds disclosed herein may be prepared, for example, by the following reaction sequence as depicted in Scheme I.

SCHEME I

Formula Il Formula I

The compounds of Formula I can be prepared, for example, following Scheme I. Thus, a compound of Formula II, wherein V is same as defined earlier (prepared as per the procedure described in WO 93/09103) is reacted with a compound of Formula III (wherein A is same as defined earlier) to yield a compound of Formula I.

The reaction of a compound of Formula II with a compound of Formula III to yield a compound of Formula I, is carried out in an organic solvent for example dimethyl formamide, acetonitrile, dimethylacetamide or dimethylsulfoxide and an organic base for example triethylamine, diisopropoylethylamine, pyridine or 1 ,2-ethylenediamine in the presence of a palladium catalyst for example tetrakistriphenylphosphine palladium (0) or dichlorobistriphenylphosphine palladium (II).

Illustrative compounds prepared following Scheme I, are;

N-({3-[2,3'-difluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 1),

N-({3-[2,6-difluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 4),

N-({2-oxo-3-[2,3',6-trifluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 6), Λ^L[(3-{3,5-difluoro-4-[6-(lH-tetrazol-l-yl)pyridin-3-yl]phenyl}-2-oxo-l,3-oxazolidin- 5-yl}methyl)acetamide (Compound No. 8),

N-[(3-{3-fluoro-4-[2-(lH-tetrazol-l-yl)pyrimidin-5-yl]phenyl}-2-oxo-l,3-oxazolidin- 5-yl}methyl)acetamide (Compound No. 9),

N-[(3-{3,5-difluoro-4-[2-(lH-tetrazol-l-yl)pyrimidin-5-yl]phenyl}-2-oxo-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 10),

Illustrative compounds which can be prepared following Scheme I, are;

N-({2-oxo-3-[2,3',5'-trifluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 2),

N-({3-[2-fluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 3),

N-( {2-0X0-3 -[2,3 ' ,5 ' 6-tetrafluoro-4 ' -( 1 H-tetrazol- 1 -yl)biphenyl-4-yl] - 1 ,3 -oxazolidin- 5-yl}methyl)acetamide (Compound No. 5),

N-[(3-{3,5-difluoro-4-[5-fluoro-6-(lH-tetrazol-l-yl)pyridin-3-yl]phenyl}-2-oxo-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 7),

N-[(3-{3,5-difluoro-4-[5-(lH-tetrazol-l-yl)-2-furyl]phenyl}-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 11),

N-[(3-{3-fluoro-4-[5-(lH-tetrazol-l-yl)-2-furyl]phenyl}-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 12),

N-[(3-{3,5-difluoro-4-[5-(lH-tetrazol-l-yl)-2-thienyl]phenyl}-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 13),

N-[(3-{3-fluoro-4-[5-(lH-tetrazol-l-yl) -2-thienyl]phenyl}-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 14).

Table I presents exemplary compounds according to Formula I

Formula I

TABLE I

Examples set forth below demonstrate general synthetic procedures for the preparation of representative compounds. The examples are provided to illustrate particular aspects of the disclosure and do not constrain the scope of the present invention as defined by the claims.

EXAMPLES

Synthesis of the starting compounds Synthesis of 2-bromo- 5 -tetrazol-1 -yl-pyrimidine.

To 2-chloro-5-bromopyrimidine (1.15 gm) was added lH-tetrazole (420 mg) and potassium carbonate (1.66 gm). The reaction mixture was stirred at elevated temperature for about 2-5 hours in the presence of N-methyl -2- pyrrolidone (NMP) (10 ml). The reaction mixture was diluted with dichloromethane, washed with water and dried over anhydrous sodium sulphate. The solvent was evaporated to yield a yellowish liquid. The product was kept over ethanol in cold to obtain a pure solid. (400 mg).

EIMS (m/z): 215.32 (M+H)

Analogues of 2-bromo-5-tetrazol-l-yl-pyrimidine viz l-(5-bromo-2-thienyl) 1-H- tetrazole andl-(5-bromo-2-furyl) 1-H-tetrazole were prepared by replacing 2-chloro-5- bromopyrimidine with appropriate thiophene and furan derivatives as applicable in each case.

Synthesis of 5-Bromo-2-tetrazol-l-yl-pyήdine.

To 5-bromo-2-aminopyridine (3.0 gm), was added sodiumazide (1.39 gm) and triethylortho formate (4.14 gm) and was stirred at elevated temperature for about 4-5 hours in the presence of acetic acid (50 ml). The solvent was evaporated under reduced pressure and residue was diluted with dichloromethane, washed with water and dried over anhydrous sodium sulphate. The solvent was evaporated to yield yellowish solid, which was recrystallized from hexane to obtain pure product (3.1 gm).

EIMS (m/z) 226.39 (M+H) Analogues of 5-bromo-2-tetrazol-l-yl-pyridine viz 5-Bromo — 3-fluoro- 2-(1H- tetrazol-1-yl) -pyridine were prepared by replacing 5-bromo-2-aminopyridine with appropriate pyridines as applicable in each case. Synthesis of 1 (4-bromo-2-fluorphenyl) lH-tetrazole.

To 4-bromo-2-fluoroaniline (25 gm) was added sodiumazide (12.5 gm) and triethylorthoformate (35 gm). The reaction mixture was stirred at elevated temperature for about 4-7 hours presence of in acetic acid (250 ml). The solvent was evaporated under reduced pressure and residue was diluted with dichloromethane, washed with water and dried over anhydrous sodium sulphate. The solvent was evaporated under reduced pressure to yield yellowish solid, which was recrystallized from hexane to obtain pure product (22 gm)

EIMS (m/z) 243.23 (M+H) Analogues of 1 (4-bromo-2-fluorphenyl) wiz 1- (4-bromophenyl) lH-tetrazole and l-(4-bromo-2, 6-difiuorphenyl) lH-tetrazole were prepared by replacing 4-bromo-2- fluoroaniline with appropriate phenyl aniline as applicable in each case.

Example 1: Synthesis of N-d3-r23'-difluoro-4VlH-tetrazol-l-yl)biphenyl-4-yll-2-oxo- l,3-oxazolidin-5-vUmethyl^*)acetamide (Compound No. 1)

To l-(4-bromo-2-fiuorphenyl) -lH-tetrazole (2.42g) and N-({3-[3-fluoro-4-

(trimethylstannyl) phenyl]-2-oxo-l,3-oxazolidin-5-yl}methyl) acetamide (4.14gm) (synthesised following the procedure as described in WO 93/09103) in presence of triethylamine (1.4ml) in dried dimethylformamide (50ml) ,purged with Argon for 15 minutes was added bisdiphenyl phosphine palladium dichloride (2.3gm) and stirred at 90- 110 ° C for about 4-5 hours. The volatiles were evaporated under reduced pressure and chromatographed using 3% methanol - dichloromethane as eluent to obtain the title compound as white solid (2.1 mg).

¹HNMR(CDCB): δ ppm δ 9.16 (s, IH), 8.04 (t, IH), 7.55 (m, 4H), 7.34 (m, IH), 6.06 (bs, IH), 4.84 (m, IH), 4.11 (m, IH), 3.86 (m, IH), 3.72 (m, 2H), 2.04 (s, 3H); Mass: 415.18 (M+H)

Analogues of N-({3-[2,3'-difluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 1) described below were prepared similarly N-CIS-^^-difluoro^'-ClH-tetrazol-l-yObiphenyM-yη^-oxo-l^-oxazolidin-S- yl}methyl)acetamide (Compound No. 4)

¹HNMR(DMSO d6): δ ppm 8.25 (s, IH), 8.06 (m, 2H), 7. 73 (m, IH), 7.50 (m, 3H), 4.79 (m, IH), 4.15 (m, IH), 3.79 (m, IH), 3.42 (m, 2H), 1.85 (s, 3H);

Mass: 415.19 (M+H).

N-( {2-0X0-3 - [2,3 ' ,6-trifluoro-4 '-( 1 H-tetrazol- 1 -yl)biphenyl-4-yl] - 1 ,3 -oxazolidin-5 - yl}methyl)acetamide (Compound No. 6)

N-[(3-{3,5-difluoro-4-[6-(lH-tetrazol-l-yl)pyridin-3-yl]phenyl}-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 8)

¹HNMR(DMSO d6): δ ppm 10.23 (s, IH), 8.77 (s, IH), 8.25 (m, 3H), 7.55 (m, 2H, 4.81 (m, IH), 4.23 (m, IH), 4.08 (m, IH), 3.80 (m, 2H), 1.85 (s, 3H);

Mass: 416.25(M+H)

N-[(3-{3-fluoro-4-[2-(lH-tetrazol-l-yl)pyrimidin-5-yl]phenyl}-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 9)

¹HNMR(DMSO d6): δ ppm 9.99 (s, IH), 8.27 (bs, IH), 8.03 (m, IH), 7.83 (m, IH), 7.61 (m, IH), 7.49 (m, 2H), 4.80 (m, IH), 4.19 (m, IH), 3.79 (m, IH), 3.51 (m, 2H), 1.85 (s, 3H);

Mass: 433.20 (M+H).

N-[(3-{3,5-difluoro-4-[2-(lH-tetrazol-l-yl)pyrimidin-5-yl]phenyl}-2-oxo-l,3-oxazolidin- 5-yl}methyl)acetamide (Compound No. 10)

¹HNMR(DMSO d6): δ ppm 10.28 (s, IH), 9.24 (s, IH), 8.27 (m, IH), 7.59 (m, 2H), 7.41 (bs, IH), 4.82 (m, IH), 4.20 (m, IH), 3.81 (m, IH), 3.44 (m, 2H), 1.85 (s, 3H);

Mass: 417.12 (M+H) Following analogues ofN-({3-[2,3'-difluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo- l,3-oxazolidin-5-yl}methyl)acetamide (Compound No. 1) described below can be prepared similarly:

N-({2-oxo-3-[2,3',5'-trifluoro-4'-(lΗ-tetrazol-l-yl)biphenyl-4-yl]-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 2),

N-( {2-0X0-3 - [2,3 ' ,5 ' 6-tetrafluoro-4 ' -( 1 H-tetrazol- 1 -yl)biphenyl-4-yl] - 1 ,3-oxazolidin-5 - yl}methyl)acetamide (Compound No. 5),

Assay for in vitro Antibacterial Activity

Compounds disclosed herein display antibacterial activity when tested by the agar incorporation method. The following ranges of minimum inhibitory concentrations (μg/ml) were obtained for representative compounds, which are given below.

S.aureus ATCC 29213 - Staphylococcus aureus ATCC 29213; MIC was 0.25 - 4 μg/ml, with linezolid 2 μg/ml and vancomycin 1 μg/ml. S.aureus MRSA ATCC 562 —Methicilline Resistant Staphylococcus aureus ATCC562; MIC was 0.25 - 2 μg/ml, with linezolid 2 μg/ml and vancomycin 1 μg/ml.

S. aureus MRSA ATCC33-- Methicilline Resistant Staphylococcus aureus ATCC33; MIC was 0.25 - 2 μg/ml, with linezolid 2 μg/ml and vancomycin 1 μg/ml. E.faecalis ATCC 29212 -Enterococcus faecalis ATCC 29212; MIC was 0.125 - 2 μg/ml, with linezolid 2 μg/ml, and vancomycin 4 μg/ml.

E.faecalis 6A F/?E ~ Vancomycin-Resistant enterococci 6A; MIC was 0.125 - 0.5 μg/ml, with linezolid 2 μg/ml, and vancomycin >16 μg/ml.

E. faecalis SP 346 A VRE — Vancomycin-Resistant enterococci SP 346A; MIC was 0.125 - 1 μg/ml, with linezolid 2 μg/ml, and vancomycin >16 μg/ml.

5. pneum. ATCC 6303 -Streptococcus pneumoniae ATCC 6303; MIC was 0.125 - 1 μg/ml, with linezolid 1 μg/ml, and vancomycin 0.5 μg/ml.

S. pneum. ATCC 49619 -Streptococcus pneumoniae ATCC 49619; MIC was 0.125 - 0.5 μg/ml, with linezolid 1 μg/ml, and vancomycin 0.25 μg/ml. 5. p«e«m. AB34 DRSP -Streptococcus pneumoniae AB34 DRSP; MIC was 0.125 - 1 μg/ml, with linezolid 1 μg/ml, and vancomycin 0.25 μg/ml.

5. pyogenes. ATCC 19615 -Streptococcus pyogenes ATCC 19615; MIC was 0.06 - 0.25 μg/ml, with linezolid 0.5 μg/ml, and vancomycin 0.5 μg/ml.

B.fragillus ATCC 25285 - Bacillus fragillus ATCC 25285 ; MIC was 2 - 8 μg/ml, with linezolid 4 μg/ml, and vancomycin not determined.

For Linezolid resistant strains

S.aureus ATCC 13709 - Staphylococcus aureus ATCC 13709; MIC was 2 - 8 μg/ml, with linezolid >64 μg/ml, and vancomycin 1 μg/ml.

S.aureus MRSA 32 —Methicilline Resistant Staphylococcus aureus 32; MIC was 2 - 8 μg/ml, with linezolid >64 μg/ml, and vancomycin 0.5 μg/ml.

E.faecalis 427 —Enterococcus faecalis 427; MIC was 1 - 16 μg/ml, with linezolid >64 μg/ml, and vancomycin 1 μg/ml.

E.faecalis 303 —Enterococcus faecalis 303; MIC was 0.125 - 4 μg/ml, with linezolid >64 μg/ml, and vancomycin 1 μg/ml. -S. pneum. ATCC 6303 -Streptococcus pneumoniae ATCC 6303; MIC was 1 - 32 μg/ml, with linezolid >16 μg/ml, and vancomycin 0.5 μg/ml.

The in vitro antibacterial activity of the compounds was demonstrated by the agar dilution method (NCCLS M 7-A5 and M 100-S8 documents). Briefly, the compounds were dissolved in dimethylsulphoxide and doubling dilution of the compounds was made in distilled water/ dimethylsulphoxide as per NCCLS method, dilutions were incorporated into Muller Hinton agar before solidification. Inoculum was prepared by direct colony suspension in normal saline solution and adjusting the turbidity to 0.5 McFarland turbidity and subsequently diluting as per NCCLS guidelines in order to obtain 10^ CFU/spot. CFU/ml of few randomly selected cultures was performed. The cultures were replicated on agar plates using Denley's multipoint replicator. The agar plates were incubated for 18 hours-24 hours (24 hours for MRSA studies) at 35+ 2⁰C. Q. C. strains were also included in each run of the study.

The in vitro activity for Haemophilus MICs were performed by using Micro broth dilution method as follows:

Media used : Mueller Hinton Broth ( MHB-DIFCO) - Cation adjusted + 5 grams per liter Yeast extract + supplements

Preparation of drug concentrations in 96 well microtitre plates was done as per the NCCLS method. Inoculum was prepared by direct colony suspensions in normal saline and adjusted to 1 McFarland turbidity and subsequently diluted in broth 100 times as per NCCLS guidelines in order to obtain 105 CFU/spot.

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 MICs against standard antibiotics were within the acceptable range. While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are included within the scope of the present invention.

Claims

We Claim: 1. Compounds having the structure of Formula I

Formula I and their pharmaceutically acceptable salts, pharmaceutically acceptable solvates, esters, enantiomers, diastereomers, N-oxides, polymorphs, prodrugs or metabolites, wherein V is selected from hydrogen and fluorine; and A is selected from the group consisting of:

with the provisio that when A is pyridinyl, then V is fluorine. 2. A compound selected from the group consisting of: N-({3-[2,3'-difluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 1),

N-({2-oxo-3-[2,3',5'-trifluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-l,3-oxazolidin- 5-yl}methyl)acetamide (Compound No.

2),

Λ/-({3-[2-fluoro-4'-(lH^"-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 3), N-({3-[2,6-difluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-2-oxo-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 4),

N-({2-oxo-3-[2,3',5'6-tetrafluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 5),

N-({2-oxo-3-[2,3',6-trifluoro-4'-(lH-tetrazol-l-yl)biphenyl-4-yl]-l,3-oxazolidin-5- yl}methyl)acetamide (Compound No. 6),

N-[(3-{3,5-difluoro-4-[5-fluoro-6-(lH-tetrazol-l-yl)pyridin-3-yl]phenyl}-2-oxo- l,3-oxazolidin-5-yl}methyl)acetamide (Compound No. 7),

N-[(3-{3,5-difluoro-4-[6-(lH-tetrazol-l-yl)pyridin-3-yl]phenyl}-2-oxo-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 8),

N-[(3-{3-fluoro-4-[2-(lH^"-tetrazol-l-yl)pyrimidin-5-yl]phenyl}-2-oxo-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 9),

N-[(3-{3,5-difluoro-4-[5-(lH-tetrazol-l-yl)-2-furyl]ρhenyl}-2-oxo-l,3-oxazolidin- 5-yl}methyl)acetamide (Compound No. 11),

^[(S-IS-fluoro^-fS^lH-tetrazol-l-yO^-furylJphenylj^-oxo-l^-oxazolidin-S- yl}methyl)acetamide (Compound No. 12),

N-[(3-{3,5-difluoro-4-[5-(lH-tetrazol-l-yl)-2-thienyl]phenyl}-2-oxo-l,3- oxazolidin-5-yl}methyl)acetamide (Compound No. 13),

N-[(3-{3-fluoro-4-[5-(lH-tetrazol-l-yl) -2-thienyl]phenyl}-2-oxo-l,3-oxazolidin- 5-yl}methyl)acetamide (Compound No. 14), or their their pharmaceutically acceptable salts, pharmaceutically acceptable solvates, esters, enantiomers, diastereomers, N-oxides, polymorphs, prodrugs or metabolites.

3. A pharmaceutical composition comprising a pharmaceutically effective amount of compound according to claim 1 or pharmaceutically acceptable salt(s) thereof with a pharmaceutical acceptable carrier for treating microbial infections.

4. A method of treating or preventing microbial infections in a mammal comprising administering to the mammal, the pharmaceutical composition according to claim 3.

5. The method according to claim 4 wherein the microbial infections are caused by gram-positive and gram-negative bacteria.

6. The method according to claim 5, wherein the gram-positive bacteria are selected from the group consisting of Staphylococcus spp., Streptococcus spp., Bacillus spp., Corynebacterum spp., Clostridia spp., Peptostreptococus spp., Listeria spp. and Legionella spp.

7. A method of treating or preventing aerobic and anaerobic bacterial infections in a mammal comprising administering to said mammal, a therapeutically effective amount of a compound according to claim 1.

8. A process of preparing a compound of Formula I,

SCHEME I

Formula Il Formula I

wherein V is selected from hydrogen and fluorine; and A is selected from the group consisting of:

with the provisio that when A is pyridinyl then V is fluorine, the process comprising reacting a compound of Formula II with a compound of Formula III to yield a compound of Formula I.

9. The process according to claim 8 wherein the reaction of a compound of Formula - II with compound of Formula III to yield a compound of Formula I, is carried out in an organic solvent selected from dimethyl formamide, acetonitrile, dimethylacetamide and dimethylsulfoxide.

10. The process according to claim 9 wherein the reaction is carried out in dimethyl formamide.

11. The process according to claim 8 wherein the reaction of a compound of Formula II with compound of Formula III to yield a compound of Formula I is carried out in the presence of an organic base selected from triethylamine, diisopropoylethylamiine, pyridine and 1,2-ethylenediamine.

12. The process according to claim 11 wherein the reaction is carried out in the presence of triethylamine.

13. The process according to claim 8 wherein the reaction of a compound of Formula II with compound of Formula III to yield a compound of Formula I is carried out in the presence of palladium catalyst dichlorobistriphenylphosphine palladium (II) and tetrakistriphenylphosphine palladium (0).

14. The process according to claim 13 wherein the reaction is carried out in the presence of dichlorobistriphenylphosphine palladium (II).

15. The process according to claim 8, wherein the reaction of a compound of Formula II with compound of Formula III to yield a compound of Formula I is carried out at a temperature range of about -70⁰C to about 18O⁰C.