2-(R)-(tert-butyldimethylsilanoxy)-3-(4-triisopropylsilanyloxy-phenyl)-propionic acid

(R)-2-[(R)-2-(tert-Butyl-dimethyl-silanyloxy)-3-(4-triisopropylsilanyloxy-phenyl)-propionylamino]-4-methyl-pentanoic acid

(S)-2-[(R)-2-(tert-Butyl-dimethyl-silanyloxy)-3-(4-triisopropylsilanyloxy-phenyl)-propionylamino]-4-methyl-pentanoic acid