(3S,3'S)-2-(3-acetoxy-3-methoxycarbonylpropanamido)-3-t-butoxycarbonylpropionic acid

(2S,3'S)-2-(3-acetoxy-3-methoxycarbonylpropanamido)-3-benzyloxycarbonylpropionic acid t-butyl ester

methyl (S)-1-((S)-3-amino-4-methoxy-4-oxobutanoyl)azetidine-2-carboxylate

methyl (S)-1-((S)-3-((S)-3-acetoxy-4-methoxy-4-oxobutanamido)-4-methoxy-4-oxobutanoyl)azetidine-2-carboxylate

tert-butyl (2S,3'S)-2-(3'-acetoxy-N-tert-butoxycarbonyl-3'-tert-butoxycarbonylpropylamino)-4-oxobutanoate