Syntheses of some thiol esters for acylation of proteins

A series of thiol esters, and S -esters of thiocarbamic acid, has been prepared by making mercapto-acetic acid or 2-mercaptoethanesulfonic acid react with carboxylic acid chlorides or with isocyanates. Aqueous solutions of these products are stable to hydrolysis but rapidly acylate amines. Azo-dyes that incorporate these reactive groups have been synthesized.