Synthesis and Antimicrobial Evaluation of Substituted Oxazolidinones Moieties

 

Pankaj Kumar*, Jennifer Fernandes, Abhishek Kumar

Department of Pharmaceutical Chemistry, NGSM Institute of Pharmaceutical Sciences, Nitte University, Paneer, Deralakatte-575018, Mangalore, Karnataka.

 

ABSTRACT:

In order to develop relatively small molecules as pharmacologically active molecules, a series of oxazolidinones having benzo thiazinen moieties and their derivatives were synthesized, and characterized by IR, ¹H NMR and Mass spectral studies. Oxazolidinones were prepared from R-glycidylbutarate and Para bromo aniline. Various substituted oxazolidinones benzo thiazinen were prepared by simple reflux in the presence of acetonitrile. Treatment of these oxazolidinones benzo thiazinen deravatives with methanesulfonyl gives its sulphonates derivatives on further treatment with sodium azide and tri phenyl phosphine in acetic anhydride to give its acetamide derivatives. All the newly synthesized compounds were evaluated for antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa.

 

 

 

INTRODUCTION:

The appearance to bacterial resistance to the antibiotics has become a matter of high concern for health care professionals since last ten years¹ . In particular, multi-drug-resistant Gram-positive bacteria including Methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis (MRSE)² and vancomycin-resistant Enterococci (VRE) are matter of high concern³ . A new class of synthetic antibiotic was developed which contain a heterocyclic ring as oxazolidinone, and showed much better effect against a large number of Gram-positive organisms. The first molecule was linezolid which contains oxazolidinone and was approved for the treatment of Gram-positive bacterial infections in humans ⁴ . 

 

Due to resistance to certain type of bacterial strain, difficulty in dose regimen and certain life threatening side effect back up the research to molecule containing oxazolidinone. Literature also shows enormous progress to oxazolidinone posing molecule⁵ . At the top now maximum focus is done on substituted phenyl oxazolidinone.

 

MATERIALS AND METHODS:

All the chemicals were of analytical grade: R-glycidyl butarate and Para bromo aniline, substituted benzothiazine, sodium azide and tri phenyl phosphine in acetic anhydride. Melting points were determined by open capillary method and are uncorrected. The purity of the compounds was monitored by thin layer chromatography (TLC) using silica gel G plates. The spots were visualized under UV light and by the exposure to iodine vapors. The homogeneity of the compounds were checked on silica gel-G coated plate by using Ethylacetate: cyclohexane as solvent. IR spectra were recorded in Alpha Bruker using ATR method. ¹H NMR spectra were recorded on Bruker spectrophotometer (400 MHz) in DMSO-d₆ solvent using tetra methyl silane (TMS) as an internal standard. Mass spectra was recorded by LCMS method.

General Procedure:

The synthesis consists of the four major steps which are as follows:

1.    Synthesis of 5-(hydroxymethyl)-3-(4-(4-methyl-3,4dihydro-2H-benzo[b][1,4]thiazin-3-ylamino)    phenyl) oxazolidin-2-one derivatives from benthiazine amines derivatives and (3-(4-fluropheny)methylene oxazolidine-5yl by simple reflux for three hours using acetonitrile solvent ⁶.

2.    Conversion of 5-(hydroxymethyl)-3-(4-(4-methyl-3,4dihydro-2H-benzo[b][1,4]thiazin-  3-ylamino) phenyl) oxazolidin-2-one derivatives to its methane  sulfonate derivatives by using triethylamine in DCM later methanesulfonyl chloride added drop wise under vigorous stirring. Stirring for an additional 10–15 min completed the reaction ⁷ .

3.    3-(4-(3,4dihydro-2h-benzo[b] [1,4] thiazin-3-ylamino) phenyl)-oxoxazolindin-5-yl) methyl methane sulfonate derivatives was convertated  to azido derivatives by treating with sodiumazide in N,N-dimethyl formamide (DMF)⁷

4.    5-(Azidomethyl)-3-(4-(4-Methyl-3,4dihydro-2h-Benzo[B][1,4]Thiazin3ylamino)Phenyl) Oxazolidin -2-one was convertated to its acetamide derivatives by treating with tri phenyl phosphine and hydrochloric acid later extracted with AcOEt ⁷.

 

 

Spectral Data:

N-((3-(4-((4-chlorophenyl) (3, 4-dihydro-2H-benzo[b][1,4]thiazin 3yl) amino) phenyl)-2-Oxooxazolidin-5-yl) methyl) acetamide (PKSN1B):

IR (KBr) cm^-1: 3389(N-H), 3050 (aromatic C-H stretching), 1612 (aromatic C=C stretching), 824 (aromatic C-H deformation),

¹H NMR (d) in ppm 8.03 (1H, s, NH), 6.58-7.33 (9H, d, Ar-H), 6.66-7.21 (4H, d, Ar-H in Benzothiazine ring), 3.31(1H, d, N-C-H in Benzothiazine ring),

MS m/z (M⁺) 523.

 

N-((3-(4-((4-methoxyphenyl)(3,4-dihydro-2H benzo[b][1,4]thiazin-3-yl)amino)phenyl)2-Oxooxazolidin-5-yl) methyl) acetamide (PKSN1E):

IR (KBr) cm^-1:3386 (N-H stretching), 3002 (aromatic C-H stretching), 1670 (C=O stretching in Oxoazolidine ring)

¹H NMR (d) in ppm 8.03 (1H, s, NH), 6.58-7.27 (8H, d, Ar-H), 6.66-7.21 (4H, d, Ar-H in Benzothiazine ring), 3.31(1H, d, N-C-H in Benzothiazine ring),

MS m/z (M⁺)519.

 

Antimicrobial Activity:

All the synthesized compounds were evaluated for their minimum inhibitory concentration by tube dilution method ⁸. The synthesized test compounds were tested at different concentrations and linezolid was used as standard. Serial dilutions of the test compound was made in a liquid medium which was inoculated with a standardized number of organisms and incubated for 24 hrs. The lowest concentration of test compound preventing appearance of turbidity is considered to be the minimal inhibitory concentration (MIC). After preparation of different concentrations of the antimicrobial agent in brain heart infusion broth (by using the broth dilution method), we inoculate them with the tested organism. Then after incubation we can determine the MIC by choosing the lowest concentration in which no growth occurs.

RESULTS AND DISCUSSION:

Table 1: Physicochemical data of synthesized compound

S. No	Comp. Code	Mol. Formula	Mol. Wt	M.P0C	Rf value (solvent system)	Physical Nature	% Yield
1	PKSN1 A	C26H25FN4O3S	492	187-190	0.28  CH3COOC2H5:C6H12 20:80	White Crystal	65
2	PKSN1 B	C26H25ClN4O3S	508	190-193	0.26 CH3COOC2H5:C6H12 20:80	Yellow Crystal	67
3	PKSN1 C	C27H28N4O4S	504	172-175	0.34 CH3COOC2H5:C6H12 20:80	Pale Yellow Crystal	65
4	PKSN1 E	C27H28N4O3S	488	180-183	0.36 CH3COOC2H5:C6H12 95:5	Pale Yellow Crystal	74
5	PKSN1 F	C26H26N4O3S	477	158-160	0.24 CH3COOC2H5:C6H12 95:5	White Crystal	62

 

 

Table 2: Antimicrobial Activity data of Synthesized Compounds.

Comp Code	Minimum inhibitory concentration (µg/ml)
	B.subtilis	S.aureus	E.coli	P.aeruginosa
PKSN A	3.1	3.1	6.25	6.25
PKSN B	3.1	3.1	12.5	12.5
PKSN C	6.2	6.2	12.5	12.5
PKSN D	12.5	12.5	25	25
PKSN E	12.5	12.5	25	25
linezolid	0.78	0.78	1.56	1.56

 

Antimicrobial Activity:

Among the screened compounds, PKSNA and PKSNB have shown good antibacterial activity against gram +ve and gram -ve bacteria compared to the standard drug.

 

CONCLUSION:

This study reports the successful synthesis of substituted oxazolidinine derivatives with moderate yields and most of the synthesized compounds showed promising antimicrobial activity.

 

ACKNOWLEDGEMENTS:

The authors are thankful to Nitte University for providing the necessary facilities to carry out this research. The authors are grateful to Sequent Research Ltd, Mangalore and Central Instrumentation Facility, MIT Manipal for providing spectroscopic data.

 

REFERENCES:

1.     Shinabarger D. Mechanism of action of the oxazolidinone antibacterial agents. Expert Opin Invest Drugs. 1999;8 :1195-02.

2.     Tomasz. Antibiotic Resistance in Streptococcus pneumonia. N Engl J Med. 1994; 330:1247-51.

3.     Cui Y, Dang Y. Synthesis of novel oxazolidinone derivatives for antibacterial investigation. Curr Sci. 2005; 89:531-34.

4.     Barbachyn MR, Ford CW. Oxazolidinone structure-activity leading to linezolid. Angew Chem. 2003; 42:2010-12.

5.     Griera R, Lcopart CC, Amat M, Bosch J, Castillo JC, Huguet. Synthesis of a new series of oxazolidinones having spiro[2,4]heptane moieties. J Med Chem Lett. 2005; 15:2515-17.

6.     Arora V, Salunkhe MM, Sinha N, Sinha RK, Jain S. Synthesis and antibacterial activity of some aryloxy/thioaryloxy oxazolidinone derivative. Bioorg Med Chem Lett. 2004;14(18):4647-50.

7.     Tokuyama R, Takahashi Y, Tomita Y, Suzuki T, Yoshida T, Iwasaki N, et al. Structure-activity relationship (SAR) studies on oxazolidinone antibacterial agents. Conversion of 5-substituent on oxazolidinone. Chem Pharm Bull. 2001;49(4):347-52.

8.     Andrews JM. Determination of minimum inhibitory concentrations. J Antimicrob Chemother 2001; 48(S1): 5-16.

 

 

 

 

Received on 10.10.2016          Modified on 11.11.2016

Accepted on 21.12.2016        © RJPT All right reserved