New 2-methylisothiazolones

New N,N-bis(alkoxycarbonyl)-L-cystine bis(methylamides) 4a, 4b and N,N-bis( benzyloxycarbonyl)-L-cystine bis(methylamide) Ic have been synthesized by m ixed anhydride method from the essential amino acid L-cystine 1 in good yie ld. These cystine bis(methylamides) 4a,b,c have been cyclized with sulfuryl chloride. New 2-methyl-4-amino-3-isothiazolone and 5-chloro-2-methyl-4-ami no-3-isothiazolone hydrobromide salts 7, 8 have been obtained by deacylatio n of 2-methyl-4-(benzyloxycarbonyl)amino-3-isothiazolone 5c and 5-chloro-2- methyl-4-(benzyloxycarbonyl)amino-3-isothiazolone 6c with hydrogen bromide in acetic acid. The microbicidal effect of the new 2-methyl-3-isothiazolone s Sa,b,c; 6a,b,c; 7 and 8 compounds obtained by the above method has been i nvestigated.