(2R,4R,5S)-2-benzyl-5-tert-butoxycarbonylamino-4-(tert-butyldimethylsilanyloxy)-7-(2,4,6-trimethoxybenzylcarbamoyl)heptanoic acid

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

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

5-tert-butoxycarbonylamino-8-(tert-butyldimethylsilanyloxy)-4-oxooctanoic acid methyl ester

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