合成路线1

Reaction of chloroacetic acid (XXII) with sodium ethoxide (XXIII) in ethanol gives 2-ethoxyacetic acid ethyl ester (XXIV), which is condensed with 4-methoxybenz-aldehyde (XXV) by means of t-BuOK in THF to yield 2-ethoxy-3-(4-methoxyphenyl)-2-propenoic acid ethyl ester (XXVI). Hydrolysis of ester (XXVI) with NaOH in hot ethanol/water affords the propenoic acid derivative (XXVII), which is reduced with H2 over Pd/C in ethanol to provide racemic 2-ethoxy-3-(4-methoxyphenyl)propionic acid (XXVIII). Optical resolution of mixture (XXVIII) is performed by salt formation with 1(S)-(1-naphthyl)ethylamine (XXIX) followed by crystallization to give the diastereomeric salt (XXX), which is treated with NaOH, followed by acidification with HCl to yield 2(S)-ethoxy-3-(4-methoxyphenyl)propionic acid (XXXI). Demethylation of compound (XXXI) by reaction with NaOH and octanethiol in NMP affords 2(S)-ethoxy-3-(4-hydroxyphenyl)propionic acid (XXXII), which is esterified with ethanol/HCl to provide the corresponding ethyl ester (XXXIII). Condensation of ester (XXXIII) with the bismesylate (II) by means of either K2CO3 in 2-butanone or Na2CO3 in acetone provides 2(S)-ethoxy-3-[4-[2-[4-(methanesulfonyloxy)-phenyl]ethoxy]phenyl]propionic acid ethyl ester (XXI), which is finally hydrolyzed with NaOH or LiOH in acetone/water.