(2S,3R)-2-[(R)-2-tert-Butoxycarbonylamino-2-(4-methoxy-phenyl)-acetylamino]-3-(tert-butyl-dimethyl-silanyloxy)-3-(3-chloro-4-hydroxy-phenyl)-propionic acid ethyl ester

(2S,3R)-2-Benzyloxycarbonylamino-3-(4-benzyloxy-phenyl)-3-(tert-butyl-dimethyl-silanyloxy)-propionic acid ethyl ester

methyl (2R)-2-(tert-butoxycarbonyl)amino-2-(4-methoxyphenyl)acetate

(2S,3R)-2-Amino-3-(tert-butyl-dimethyl-silanyloxy)-3-(4-hydroxy-phenyl)-propionic acid ethyl ester