(R)-2-(4-Phenoxymethyl-benzyloxycarbonylamino)-3-phenyl-propionic acid methyl ester 6 (1.605 g, 3.83 mmol) was dissolved in methanol (40 ml) at room temperature. A solution of LiOH (177 mgs, 4.21 mmol) in 15 ml of H2O was then added and the mixture was stirred overnight. The mixture was diluted with H2O (50 ml). The methanol was then removed in vacuo. The aqueous residue was acidified with 4.5N HCl forming a precipitate that was filtered and dried. Recrystallization gave about 1.2 g of (R)-2-(4-phenoxymethyl-benzyloxycarbonylamino)-3-phenyl-propionic acid 7, mp. 115.9-116.7° C.
