(3S,4S)-4-((S)-sec-Butyl)-1-(tert-butyl-dimethyl-silanyl)-3-hydroxy-azetidin-2-one

(S)-2-(N'-tert-Butoxycarbonyl-N-{(S)-2-[(2S,3S)-2-((S)-sec-butyl)-1-(tert-butyl-dimethyl-silanyl)-4-oxo-azetidin-3-yloxy]-4-methyl-pentanoyl}-hydrazino)-4-methyl-pentanoic acid benzyl ester

(S)-2-(N'-tert-Butoxycarbonyl-N-{(R)-2-[(2S,3S)-2-((S)-sec-butyl)-1-(tert-butyl-dimethyl-silanyl)-4-oxo-azetidin-3-yloxy]-4-methyl-pentanoyl}-hydrazino)-4-methyl-pentanoic acid benzyl ester