(2S,4S)-1-[2-(1,1-Dimethyl-3-oxo-3-pyrrolidin-1-yl-propylamino)acetyl]-4-fluoro-pyrrolidine-2-carbonitrile: A potent, selective, and orally bioavailable dipeptide-derived inhibitor of dipeptidyl peptidase IV

A series of 2-[3-[2-[(2S)-2-cyano-1-pyrrolidinyl]-2-oxoethylamino]-3-methyl-1-oxobutyl]-based DPP-IV inhibitors with various monocyclic amines were synthesized. The structure-activity relationships (SAR) led to the discovery of potent DPP-IV inhibitors, having IC50 values of <100 nM with excellent selectivity over the closely related enzymes, DPP-II, DPP8, DPP9 and FAP (IC50 > 20 μM). Of these compounds, the analogues 12a, 12h and 12i exhibited a long-lasting ex vivo DPP-IV inhibition in rats.