Concise total synthesis of the prolyl endopeptidase inhibitor eurystatin A via a novel Passerini reaction–deprotection–acyl migration strategy

The Passerini reaction between suitably protected alaninal, leucine isonitrile, and ornithine components delivered adducts 10a,b in high yield. Orthogonal N-deprotection of 10a led, via a smooth O- to N-acyl migration, to 11, which constitutes the entire skeleton of the eurystatins. Subsequent deprotection, macrocyclization, elaboration, and final oxidation steps efficiently afforded eurystatin A 1a in high overall yield.