Two substituted acrylic acids, β-(2,4-dimethylbenzoyl) acrylic acid and β-(2,5-diisopropylbenzoyl) acrylic acid were reacted with six 5-substituted 2-aminobenzenethiols, in dry ethanol containing trifluroacetic acid to obtain ten new compounds, 8-substituted 4-(2,4-dimethylphenyl/2,5-diisopropylphenyl)-2,3-dihydro-1,5-benzothiazepine-2-carboxylic acids in 53-63 % yields. The products were characterized on the basis of micro analytical data and spectral analysis comprising IR, 1 H NMR and mass studies. All the synthesized compounds have been screened for their antimicrobial activity against the Gram-positive bacteria, Staphylococcus aureus and Gramnegative bacteria, Enterobacter cloacae, Klebsiella aerogenes and fungus, Candida albicans with respective reference compounds. Keywords: Acrylic acids, 5-Substituted 2-aminobenzenethiols, Antimicrobial activity.Asian Journal of Chemistry; Vol. 29, No. 10 (2017), 2221-2223 containing trifluoroacetic acid to obtain the final compounds in single step in 53-63 % yields. The purity of the final products was checked by TLC. The structures of the final products were ascertained by elemental and spectral analyses comprising IR, 1 H NMR and mass spectral studies. All the compounds 3a-l were evaluated for their antimicrobial activity, comprising antibacterial and antifungal.General procedure for the syntheses of 8-substituted 4-(2,4-dimethylphenyl/2,5-diisopropylphenyl)-2,3-dihydro-1,5-benzothiazepine-2-carboxylic acids (3a-l): To a solution of β-(2,4-dimethylbenzoyl/2,5-diisopropylbenzoyl) acrylic acid (1, 0.001 mol) in dry ethanol (5 mL) containing trifluoroacetic acid, was added the ethanolic solution of 5-substituted 2-aminobenzenethiols (2, 0.001mol) with continuous stirring. The reaction mixture after refluxing for 3-4 h followed by cooling, afforded the crude, which was filtered and crystallized from ethanol to give coloured crystals of the target compounds (3a-l).Antimicrobial activity: The antimicrobial activity of all newly synthesized compounds 8-substituted 2,3-dihydro-4-(2,4-dimethylphenyl/2,5-diisopropylphenyl)-1,5-benzothiazepine-2-carboxylic acids (3a-l), were carried out using paper disc method [11] against the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Enterobacter cloacae, Klebsiella aerogenes and antifungal activity against the fungus, Candida albicans at the concentration of 200 µg/disc, with vancomycin and polymixin B and fluconazole as the reference drugs, respectively. The reference compounds were used to evaluate the activity in the form of activityScheme-I index. Zones of inhibition, exhibited by the reference and test compounds, were measured and compared to show relative activities in the form of activity index. The physical constants and the antimicrobial activity is given in Table-1. Detection method: All the reported melting points are uncorrected. Purity of the compounds were checked by TLC on glass plates coated with silica gel 'G' as absorbent, using benzene : ethanol : aq. ammonia (50 %) in the ratio 7:2:1 as so...

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