(3R,5S)-5-((S)-1-Amino-2-phenyl-ethyl)-3-benzyl-dihydro-furan-2-one

(3S,5S)-3-benzyl-5-{(1S)-1-[(tert-butoxycarbonyl)amino]-2-phenylethyl}dihydrofuran-2-(3H)-one

{(1S)-1-[(4R)-4-(3-azido-propyl)-5-oxo-tetrahydro-furan-(2S)-2-yl]-2-phenyl-ethyl} carbamic acid tert-butyl ester

[(1S)-1-{(1S)-1-[(4R)-4-(3-azido-propyl)-5-oxo-tetrahydro-furan-(2S)-2-yl]-2-phenyl-ethylcarbamoyl}-2-(trityl-carbamoyl)-ethyl]-carbamic acid benzyl ester

(2R,4S,5S)-5-((S)-2-(((benzyloxy)carbonyl)amino)-4-oxo-4-(tritylamino)butanamido)-4-((tert-butyldimethylsilyl)oxy)-6-phenyl-2-(3-((triphenylphosphonio)amino)propyl)hexanoate