By treating β‐mercaptopropionic acid with aryl (aralkyl) isothiocyanates in weak alkaline medium, the authors have obtained the corresponding β‐(N‐aryl(aralkyl)‐thiocarbamoylthio)‐propionic acids which, heated 2 hours at 120°, yield the corresponding 3‐aryl(aralkyl)‐4‐oxo‐2‐thiono‐tetrahydrothiazines.

2-(N-phenylthiocarbamoylthio)-l-diethylamino-ethanies obtained by treating 1-diethylamino-2-mercapto-ethane with phenyl isothiocyanate in hydrogenocarbonate + pyridine medium.

Cysteine (K or Na salts) reacted with 2 molecules of an aryl isothiocyanate in alcohol-pyridine medium at room temperature yields the corresponding N, S-diarylthiocarbamoylated derivatives which, treated with glacial acetic acid (10 vol.) + concentrated HCl (1 vol.), are transformed into the corresponding S-arylthiocarbamoylated derivatives of arylthiohydantoh-cysteine.