Chemistry of the Podocarpaceae. XLIX. Isomerization of 12-Methoxy-19-norpodocarpatetraenes

Abstract

Methods for isomerization of the 12-methoxy-19-norpodocarpatetraene mixture obtained from oxidative decarboxylation of 12-methoxypodocarpa-8,11,13-trien-19-oic acid (1) with lead tetraacetate have been examined. Acid-catalysed isomerization gives a mixture of the endocyclic isomers (11) and (19) while iodine-catalysed isomerization gives a mixture enriched in the isomer (19) to the extent of 80%. Metal-catalysed decarbonylation of the acid chloride (6) and oxidative decarboxylation of the acetoxy acid (7) have also been examined.