1,2-Pyrrolidinedicarboxylic acid, 5-oxo-, 1-(phenylmethyl) ester, (S)- 1-Benzyl hydrogen (S)-5-oxopyrrolidine-1,2-dicarboxylate 32159-21-0 EINECS 250-936-0 N(alpha)-Carbobenzoxypyroglutamic acid