Abstract
A number of amino acid derivatives of DL-Zra/w-epoxysuccinic acid, with a general formula of R1O-ES-AA-OR2 (ES, DL-trans-epoxysuccinyl group; AA, amino acid residue) were newly synthesized and used for the study of structure-activity relationships of papain inhibition. Branched-alkyl amino acids, such as Leu, He and Val, as AA and hydrogen or an alkyl group substituted with a phenyl or cycloalkyl group as R1 were desirable for activity, respectively. However, R2 or the optical activities of ES and AA not so much influenced on the activity.