To a solution of 1,2-aminothiol and Na 2 CO 3 in a minimum volume of water, a previously prepared solution of acetic anhydride (1.05 equiv.) and formic acid (1.2 equiv.) was added. The pH of the solution was kept alkaline by addition of solid Na 2 CO 3 and the solution was stirred for 60 min. The remaining solids were removed by filtration and the cake washed three times with CHCl 3 . The organic phase was neutralized (6N HCl) and concentrated. The residue was ...