Chemistry of the Podocarpaceae. XX. Epoxides of ring-A-unsaturated 12-Methoxypodocarpa-8,11,13-trienes

Abstract

Selective epoxidation of the methoxy alkene mixture (IX) from oxidative decarboxylation of 12-methoxypodocarpa-8,11,13-trien-19-oic acid (I) provides a method of obtaining a high yield of the exocyclic alkene (VII) from the mixture. Isolation of the 3α,4α-epoxide (X) during the epoxidation allows the formation of C 3 oxygenated derivatives of 12- methoxypodocarpa-8,11,13-trien-19-oic acid.     Methods for opening the epoxide ring of (X) and of the 4α,5α- and 4α,19-epoxides, (XI) and (XII), have been examined, and the structures of the products from rearrangement of each epoxide with boron trifluoride have been assigned.