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

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

(S)-4-carboxymethyl-2-azetidinone

p-nitrobenzyl (diphenylmethyloxycarbonyl)acetate

(S)-N-(diphenylmethyloxycarbonyl)methyl-2-azetidinone