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Sixteen compounds of 2-aminobenzothiazole derivatives were synthesized from alkyl (C1-5) p-aminosalicylate by thiocyanation reaction. The NMR spectra of synthesized compounds showed that they were actually mixture of 5-hydroxy-6-alkoxycarbonyl-2-aminobenzothiazole [alkoxy=methoxy (Ia), ethoxy (IIa), n-propoxy (IIIa), iso-propoxy (IVa), n-butoxy (Va), iso-butoxy (VIa), n-amoxy (VIIa), iso-amoxy (VIIIa)] and 7-hydroxy-6-alkoxycarbonyl-2-aminobenzothiazole [alkoxy=methoxy (Ib), ethoxy (IIb), n-propoxy (IIIb), iso-propoxy (IVb), n-butoxy (Vb), iso-butoxy (VIb), n-amoxy (VIIb), iso-amoxy (VIIIb)]. The mixtures of two isomeric benzothiazole were separated by way of preparative TLD. The formation ratio of these two isomers varied with the kind of alkyl chain in alkyl p-aminosalicylate. These compounds were subjected to the test for antimicrobial activities using Staphylococcus aureus and Escherichia coli by tube dilution method. The seven compounds, Ia, IIa, IIIa, VIa, IIIb, IVb and Vb, showed inhibition of the growth of S. aureus at the concentration of 10mcg/ml and Ib, IIb, IVa, VIIa, and VIIIa exhibited antimicrobial activities against S. aureus at the concentration of 100mcg/ml. As to the growth of E. coli, IVb, VIb, VIIb, and VIIIb were observed inhibition at the concentration of 1mcg/ml. Ia, IIa, IIIa, VIIa, Va, VIIIa, and IIb exhibited potential antimicrobial activities against E. coli at the concentration of 10mcg/ml. Ib, IIIb, IVa, and VIa showed inhibition of the growth of E. coli at the concentration of 100mcg/ml.
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