(4R,5S)-5-tert-butoxycarbonylamino-8-(tert-butyldimethylsilanyloxy)-4-hydroxyoctanoic acid methyl ester

(S)-2-[N-(tert-butoxycarbonyl)amino]-5-hydroxypentanoic acid benzyl 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