The (.+-.)-1-(4-Methoxyphenyl)ethyl Ester as a Carboxyl Protecting Group.

Abstract Unhindered carboxylic acids were converted to their (±)-1-(4-methoxyphenyl)ethyl (Mpe) esters in good yields by condensation with (±)-1-(4-methoxyphenyl)ethanol under mild conditions. The Mpe esters were rapidly and quantitatively cleavable by either 1% TFA in CH 2 Cl 2 or 10% DCA in CH 2 Cl 2 , conditions which leave Boc, t-butyl ester and ether intact. An Mpe ester was removed by hydrogenolysis much more slowly than the analogous benzyl ester.