4-Hydroxy-
L-proline was converted into the tetrahydrooxepino[4,3-
b]pyrrole ring system characteristic of the potent antitumor agent MPC1001.Key steps were regioselective formation of a vinylogous amide by use of Bredereck's reagent and acid-induced cyclization of an alcohol ontothe carbon-carbon double bond of that amide by addition-elimination to generate the seven-membered oxacyclic subunit.