A synthesis of terfenadine carboxylate, 1, a metabolite of terfenadine
2, is described. In the key step, the sodium salt of 2-(4-bromophenyl
)-2-methylpropionic acid, 7, was lithiated via a metal-halogen exchang
e using t-BuLi and subsequently condensed with ydroxydiphenylmethyl-pi
peridin-1-yl]butyraldehyde, 5, to afford terfenadine carboxylate, 1.