Total Synthesis of (−)-Colchicine by an Oxyallyl [4+3] Cycloaddition

An enantioselective synthesis of (−)-colchicine, free from isocolchicine, is delineated and features tandem application of the intramolecular Diels–Alder reaction of acetylene-tethered oxazoles and the [4+3] cycloaddition of oxyallyls. This work underscores the synthetic utility of little explored α-alkoxy substituted oxyallyls.