Synonyms: Butanoicacid, 4-[(2,5-dioxo-1-pyrrolidinyl)oxy]-3-[[(9H-fluoren-9-ylmethoxy)carbonyl]amino]-4-oxo-,1,1-dimethylethyl ester, (3S)- (9CI); Butanoic acid,4-[(2,5-dioxo-1-pyrrolidinyl)oxy]-3-[[(9H-fluoren-9-ylmethoxy)carbonyl]amino]-4-oxo-,1,1-dimethylethyl ester, (S)-