INTRODUCTION:

A number of poly substituted, poly hetrocyclic compounds display significant pharmacological activities. Among those 1, 4 Benzothiazine have been extensively investigated¹. The literature survey reveals that 1, 4 thiazine comprises an important moiety and their pharmacological activity reported as antibacterial antifungal and antifungal agent^2-4.

The proposed work involves the synthesis of (3-oxo-3, 4-dihydro-2H-1,4-benzothiazin-2-yl)acetic acid form reaction of O-Amino Thiophenol and maleic anhydride. (3-oxo-3, 4-dihydro-2H-1,4-benzothiazin-2-yl) acetate prepared by Esterification of (3-oxo-3, 4-dihydro-2H-1, 4-benzothiazin-2-yl) acetic acid. Further Mannich base condensation of these moieties along with Aromatic amines has been carried out.

Antimicrobial activity:

A. Antibacterial activity:

All synthesized compounds were screened for their antibacterial activity against strains viz. E. coli, E.fecalis, Klebshilla and S. aureus. The antibacterial activity is performed using Tube Dilution method for determination of Minimum inhibitory concentration (MIC). Streptomycin was used as standard drug.

B. Anti fungal activity:

All synthesized compounds were screened for their antifungal activity against strains viz. C. albican and Aspergillus Niger. The antifungal activity is performed using Tube Dilution method for determination of Minimum inhibitory concentration (MIC). Fluconazole was used as standard drug⁵.

MATERIAL AND METHOD:

Melting points were determined in open capillary method and are uncorrected. IR spectra were recorded on Shimadzu IR 200 spectrometer using KBr pellets method. The ¹H NMR spectra were recorded on Bruker AC 400 MHz using DMSO as solvent and tetra methyl silane as internal standard.

Proposed scheme:

General Procedure

1. Synthesis of (3-oxo-3, 4-dihydro-2H-1, 4-benzothiazin-2-yl) acetic acid⁶

To a solution of Maleic anhydride (0.05 mol) in diethyl ether (20 ml) a solution of o-Amino thiophenol (0.05 mol) in diethyl ether (20 ml) was added. The reaction mixture was stirred at room temperature for 2 hrs. The precipitate was filtered and washed with diethyl ether and crystallized with ethanol to get needle shape crystals of pure compound yield is 96 % and m.p. is 201⁰C

2. Synthesis of ethyl (3-oxo-3, 4-dihydro-2H-1, 4-benzothiazin-2-yl) acetate⁷:

(3-oxo-3, 4-dihydro-2H-1, 4-benzothiazin-2-yl) acetic acid (2.0 mol) was added in sufficient amount of alcohol to dissolve, 3-4 drops of Conc. H₂SO₄ was added and Refluxed the reaction mixture for 6-7 hours. The content was evaporated to remove alcohol, the ppt. occurs; to this 5-10 % sodium bicarbonate was added till effervescence ceases. Further, reaction mixture was extracted with Diethyl Ether. Ethereal layer was dried over anhydrous Sodium Sulphate. Ether was evaporated, Ester appears, m. p. 125⁰C, yield 80 %

3. General Procedure for Mannich base condensation⁸:

A mixture of compound (3-oxo-3, 4-dihydro-2H-1, 4-benzothiazin-2-yl) acetic acid (0.01 mol) in ethanol, formaldehyde (0.02 mol) and substituted Sulphonamide was added. The reaction mixture was refluxed for 4-5 hrs. The solvent was poured in ice water, resulting solid were filtered off dried and recrystallized using appropriate solvent.

Analytical data of the synthesized compounds:

BSN IR (KBr) cm^-1: 3317 (-OH str), 3120 (NH str), 3068 (Ar C-H), 1666 (C=O), 655(C-S str)

BSC IR (KBr) cm^-1: 3282 (-OH str), 3101 (NH str), 3051 (Ar C-H), 1668 (C=O), 655(C-S str)

BSM IR (KBr) cm^-1: 3320 (-OH str), 3203 (NH str), 3065 (Ar C-H), 16687 (C=O), 684(C-S str). ¹H NMR: 2.282- (m, 3H, -CH₃), 2.661-2.532-( s, 1H, -NH), 2.90 (m, 2H, -CH₂-), 3.357- (s, 2H, -CH₂), 3.86-( s, 2H, -CH₂).

BSP IR (KBr) cm^-1: 3317 (-OH str), 3120 (NH str), 3068 (Ar C-H), 1666 (C=O), 655(C-S str)

BESC IR (KBr) cm^-1: 3207 (NH str), 2984 (Ar C-H), 1667 (C=O), 655(C-S str)

BESP IR (KBr) cm^-1: 3242 (NH str), 3070 (Ar C-H), 1664 (C=O), 655(C-S str)

BESM IR (KBr) cm^-1: 3205 (NH str), 3072 (Ar C-H), 1667 (C=O), 655(C-S str)

BESN IR (KBr) cm^-1: 3203 (NH str), 3068 (Ar C-H), 1666 (C=O), 655(C-S str)

Antimicrobiological screening:

All synthesized compounds were screened for their antibacterial activity against strains viz. E. coli, E.fecalis, Klebshilla and S. aureus and antifungal activity against strains viz. C. albican and Aspergillus Niger.

Comp ound	E. Coli	Kleb siella	E. Fecaelis	S. Aureus	C. Albican	A. Niger
BSN	50	50	12.5	25	50	50
BSC	50	50	25	20	50	50
BSM	6.25	6.25	3.125	3.125	6.25	6.25
BSP	25	25	25	12.5	25	12.5
BESN	50	50	12.5	50	50	25
BESC	50	50	50	25	50	50
BESM	12.5	12.5	6.25	6.25	12.5	12.5
BESP	25	25	6.25	25	25	25

RESULT AND DISCUSSION:

Antibacterial Activity:

Synthesized compounds from (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2-yl)acetic acid and (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2-yl)acetate were screened for their antibacterial activity against S aureus, Klebsiella, E.fecaelis and E. coli. Amongst them BSM and BESM show very significant activity at concentraion at 3.15 µg/ml and 6.125 µg/ml respectively. Compounds BSP and BESP shows moderate antibacterial activity. For the antibacterial activity streptomycin used as a internal standard.

Antifungal Activity:

Synthesized compounds from (3-oxo-3, 4-dihydro-2H-1,4-benzothiazin-2-yl)acetic acid and (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2-yl)acetate were screened for their antifungal activity against C. albican and Aspergillus Niger. Amongst them compound BSM and BESM shown significant activity at concentration 6.25 µg/ml and 12.5 µg/ml respectively. Compounds BSP and BESP shows moderate antifungal activity. For the antifungal activity, Fluconazole used as a internal standard.

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Received on 13.09.2011 Modified on 24.09.2011

Asian J. Research Chem. 4(11): Nov., 2011; Page 1661-1663