(2S)-2-[(tert-butoxycarbonyl)amino]pent-4-enoic acid
ethyl (R)-2-[(tert-butoxycarbonyl)amino]pent-4-enoate
methyl (2S)-2-tert-butoxycarbonylamino-4-pentenoate
t-butyl (2S,4S)-5-[N',N''-bis(benzyloxycarbonyl)guanidino]-2-N-(9-phenyl-9H-fluoren-9-yl)amino-4-N-(2-trimethylsilylethanesulfonyl)aminopentanoate