Total Synthesis of Leupyrrin B1: A Potent Inhibitor of Human Leukocyte Elastase.

The total synthesis of leupyrrin B1 was accomplished by an expedient strategy that involves an optimized HATU-mediated amide coupling protocol of elaborate substrates. The generally useful procedure was also successfully applied in an improved total synthesis of leupyrrin A1. Finally, leupyrrins A1 and B1 were evaluated toward a panel of proteases, and human leukocyte elastase was discovered as a molecular target of the leupyrrins.