Synthese von Carbobenzoxy‐dipeptid‐p‐nitrophenylestern. Über aktivierte Ester IX

A study of the preparation of carbobenzoxy‐dipeptide p‐nitrophenyl esters revealed that partial racemization may occur depending on the structure of the dipeptide derivative used. Whereas carbobenzoxy‐S‐benzyl‐ L ‐cysteinyl‐ L ‐tyrosine yielded an optically pure ester employing the sulfite method, the synthesis of the ester of carbobenzoxy‐ L ‐tyrosine by various methods proceeded with partial racemization. The optically pure carbobenzoxy‐ L ‐seryl‐ L ‐tyrosine p‐nitrophenyl ester was obtained by condensation of carbobenzoxy‐ L ‐serine with p‐nitrophenyl L ‐tyrosinate.