5-methyl 1-hydrogen (S)-3-benzylaminoglutarate

1-benzyl 5-methyl (R)-3-tert-butoxycarbonylaminoglutarate

(S)-4-carboxymethyl-2-azetidinone

(R)-4-3'-diazo-3'-p-nitrobenzyloxycarbonyl-2'-oxopropyl-2-azetidinone

(4R) N-Benzyl-4-methoxycarbonylmethyl-azetidin-2-one