The reaction between 6-acetyl-3-alkyl-1-ethoxy-3, 4, 5a, 6, 11, 11a-hexahydro-10bH- pyrazino-[2′, 1′-5, 1] pyrrolo [2, 3-b] indole-1, 4-diones and anthranilic acid was studied from a stereochemical point of view. Various degrees of epimerization of the tryptophan and alanine stereocenters were observed in compounds with a cis relationship between their H- 3 and H-11a hydrogen atoms, and stereochemistry was retained in the trans compounds. ...