In analogy with Example 5f), 5.0 g (7.85 mmol) of 5(S)-(Boc-amino)-4(S)-hydroxy-6-phenyl-2(R)-{[p-(2,6-dichlorobenzylsulfonyl)phenyl]methyl}hexanoic acid in 74 ml of DMF are silylated with 5.4 g (36.1 mmol) of tert-butyldimethylchlorosilane and 4.4 g (64.4 mmol) of imidazole. Hydrolysis of the silyl ester function with 6.5 g of potassium carbonate in 85 ml of methanol, 22 ml of THF and 22 ml of water yields the title compound after column chromatography (SiO2, hexane/ethyl acetate, 1:1) and stirring-up with DIPE: TLC Rf (C)=0.5; tRet (II)=21.0 min.
