Development of a Scalable Synthesis of Dipeptidyl Peptidase-4 Inhibitor ABT-279

A convergent, scalable synthesis of dipeptidyl peptidase-4 inhibitor, ABT-279, has been developed and demonstrated on multikilogram scale. The cis-2,5-disubstituted pyrrolidine is generated by cyclization of a Boc-amine onto an alkynyl ketone followed by stereospecific reduction of the resulting acyliminium intermediate. The amine coupling partner was prepared by a novel Hofmann rearrangement promoted by 1,3-dibromo-5,5-dimethylhydantoin. The final product was isolated as the l-malic acid salt. The scale-up campaign consisted of 15 steps and delivered 42 kg of ABT-279 in 14% overall yield. A second-generation synthesis that addresses some of the issues encountered during scale-up was developed and demonstrated on kilogram scale.