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

(2S)-2-tert-butoxycarbonylamino-5-(tert-butyldimethyl-silanyloxy)-pentanoic acid

[(1S)-1-[(4R)-4-benzyl-5-oxotetrahydrofuran-(2R)-2-yl]-3-(2,4,6-trimethoxybenzylcarbamoyl)propyl]carbamic acid tert-butyl ester

(2S)-N'-[2-tert-butoxycarbonylamino-5-(tert-butyl-dimethyl-silanyloxy)-pentanoyl]-N-methyl-hydrazinecarboxylic acid benzyl ester