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

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

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

[3-tert-butoxycarbonylamino-6-(tert-butyldimethylsilanyloxy)-2-oxohexyl]phosphonic acid dimethyl ester