4.76 g (37.5 mmol) of oxalyl chloride in 33.6 ml of methylene chloride are treated dropwise, at -60° C. and under a N2 atmosphere, with a solution of 3.5 ml (49 mmol) of DMSO in 60 ml of methylene chloride. After the mixture has been stirred for 15 min, 8.94 g (25 mmol) of (S)-N-Boc-(p-benzyloxyphenylalaninol) in 150 ml of methylene chloride are added, and this mixture is subsequently stirred for about 25 min. 14 ml (100 mmol) of triethylamine in 30 ml of methylene chloride are then added and the mixture is stirred for 30 min. 222 ml of a 20% of a KHSO4 solution and 187 ml of hexane are added, and the mixture is warmed to 0° C. The aqueous phase is separated off and extracted 2× with ethyl acetate. The organic phases are washed with saturated NaHCO3 solution and saline, dried with Na2SO4 and evaporated to give the title compound: TLC Rf (C)=0.71; 1H-NMR (200 MHz, CDCl3): 1.44 (s, 9H), 3.06 (d, J=6 Hz, 2H), 4.39 (m, 1H), 5.03 (s+sb, H2C--O+HN), 6.86-6.98 and 7.03-7.15 (2m, each 2H), 7.30-7.48 (m, 5H), 9.62 (s, 1H).
