Short Synthesis of a Proline Amide Orexin Receptor Antagonist on the Pilot Plant Scale

A three-step fully telescoped synthesis of an N-sulfonyl proline amide, a nonpeptide antagonist of human orexin receptors, is described. The process development from the medicinal chemistry route up to the 240 kg production of 1 is discussed with a focus on an economical and efficient amide bond formation and identification of a new polymorph. The routes are compared using green metrics.