[(1S)-1-[(4R)-4-benzyl-5-oxotetrahydrofuran-(2R)-2-yl]-4-hydroxybutyl]carbamic acid tert-butyl ester

(4S)-4-[(4R)-4-benzyl-5-oxotetrahydrofuran-(2R)-2-yl]-4-[bis(tert-butoxycarbonyl)amino]butyric acid

[(1S)-1-[(4R)-4-benzyl-5-oxotetrahydrofuran-(2R)-2-yl]-4-(tert-butyldimethylsilanyloxy)butyl]carbamic acid tert-butyl ester

(2R,4R,5S)-2-benzyl-5-tert-butoxycarbonylamino-4,8-bis-(tert-butyldimethylsilanyloxy)octanoic acid