SYNTHESIS OF S-(-PYRIDYL -N-OXIDE)N-SUBSTITUTED OR -N,N'-DISUBSTITUTED ISOTHIOUREA HYDROBROMIDES ANDTHEIRANTIM ICKOBIALACTIVITY

To obtain more potent and wide-spectrum antimicrobial agent,twenty S-(2-pyridyl-N-oxide)-N一substituted or -N’-disubstituted isothiourea hydrobromides were synthesized, nineteen of which were new。The minimum inhibitory concentrations(MICs )of these compounds against Aspergillus niger,Penicillium citrinum, Trichoderma sp.,Escherichia coli and Bacillus subtilis eere tested with the method of liquid shake culture and the antimicrobial activities were observed.The best compound was found to beS-(2-pyridyl-N-oxide)-N,N’-1,3- ethylene isothiourea hydrobromide (IIIa),and its antimicrobial　activity(MIC0.5～5ppm)was shown to be superior to that of MI861(Ia,lead compound).The　antimicrobial activities of the nine target compounds were found to be superior to that of Ia against E.coli and B.subtilis.Further research showed that IIIa is a wide-spectrum anti-microbial agent.