The pH dependence of the hydrolysis of 4-{2-[(methylsulfonyl) oxy] ethyl} phenyl methanesulfonate, 1, and two carboxylate esters, ethyl 2 (S)-ethoxy-3-(4-hydroxyphenyl) propionate, 2 and (2 S)-2-ethoxy-3-[4-(2-{4-[(methylsulfonyl) oxy] phenyl} ethoxy) phenyl] propanoate, 3, has been studied with a view to the selective removal of any remaining 1, following coupling with 2 to generate 3 in water at 95° C (Scheme 1). It is shown that ...