A process is provided for preparing a dipeptidyl peptidase IV inhibitor of the structure ##STR00001## is treated with TFAA in isopropyl acetate to protect the tertiary hydroxyl group as a trifluoroacetate group to form 4 ##STR00002## (which is a novel intermediate) which is converted to acid chloride compound 5 ##STR00003## (which is a novel compound) using Vilsmeier reagent or other chloro reaget and coupled with compound 6 in a heterogeneous mixture of ethyl acetate and aqueous bicabonate to give compound 7 ##STR00004## The N,O-bis(trifluoroacetyl) groups of compound 7 are deprotected to give free base compound 10.