DCC (1 g; 4.85 mmole) and N-hydroxy-succinimide acid (0.56 g; 4.85 mmole) were added to a solution of 2-ethoxy-3-[4-(2-{4-methanesulfonyloxyphenyl}ethoxy)phenyl]propanoic acid (described in Example 2) (1.65 g; 4.04 mmole) in acetonitrile (25 ml) at 0° C. After 1 hour a precipitate was filtered off and diisopropylethylamine (1.82 g; 14.1 mmole) and benzyl hydroxylamine (1.24 g; 8.08 mmole) dissolved in acetonitrile were added. After stirring overnight hydrochloric acid (2M) was added and the mixture was extracted with diethyl ether. The organic phase was washed with sodium carbonate solution and dried (magnesium sulfate). The solvent was removed and the crude product was purified by chromatography on silica gel using ethyl acetate:heptane (gradient 10-100% ethyl acetate) as eluant to give 1.36 g (yield 66%) of N-benzyloxy-2-ethoxy-3-[4-(2-{4-methanesulfonyloxy-phenyl}ethoxy)phenyl]propanoic amide.
