Synthesis of (R)- and (S)-(glu)Thz and the Corresponding Bisthiazole Dipeptide of Dolastatin 3

Article abstract of DOI:10.1021/jo00374a019

Dolastatin 3 (1) has been reported to be a cyclic pentapeptide containing two thiazole amino acids, (gly)Thz (2) and (gln)Thz (3).The syntheses of (R)- and (S)-(glu)Thz (8a,b) and (glu)Thz-(gly)Thz (11a,b) derivatives suitable for elaboration to dolastatin 3 are described.A key feature of the (glu)Thz syntheses is the selective thiation of a primary amide with Lawesson's reagent in the presence of ester and urethane functionalities.