Dithio and thiono. Esters. 61. Synthesis of α-Amino Dithioesters and Endothiodipeptides

The α-amino ester hydrochlorides ( 1 ) are converted into N-protected α-amino amides ( 3 ), α-amino thioamides ( 4 ) and α-amino dithiomethylesters ( 5 ). Condensation of 5 with the alkali salts of α-amino acids gives rise to the endothiodipeptide alkali salts ( 7 ).