CHEMISTRY OF PODOCARPACEAE .19. OXIDATION OF SOME PODOCARPA-8,11,13-TRIEN-19-OIC ACID DERIVATIVES WITH LEAD TETRAACETATE

A pathway involving the γ,δ-unsaturated acid (XIV) is suggested for the formation of lactones (IX) and (XII) from the oxidation of 12-methoxypodocarpa-8,11,13-trien-19-oic acid (I) with lead tetraacetate. Support for this suggestion has been obtained from an examination of the products from lead tetraacetate oxidations of 12-methoxypodocarpa-6,8,11,13-tetraen-19-oic acid (XIV), methyl 12-methoxy-podocarpa-8,11,13-trien-19-oate (II), methyl 12-methoxypodocarpa-6,8,11,13-tetraen-19-oate (XV), 12-methoxypodocarpa-8,11,13-trien-19-oic acid (XVIII), methyl 12-hydroxypodocarpa-8,11,13-trien-19-oate (III), methyl 12-acetoxypodocarpa-8,11,13-trien-19-oate (IV), 7-acetoxy-12-methoxypodocarpa-6,8,11,13-tetraen-19-oic acid (XVI), and methyl 7-acetoxy-12-methoxypodocarpa-6,8,11,13-tetraen-19-oate (XVII). Evidence is presented confirming the assignment of a 7α-configuration for the acetoxy group of the acetoxy lactone (IX), and the preparation of some bromo 7-oxo- and 6,7,19-hydroxy derivatives of 12-methoxypodocarpa-8,11,13-trien-19-oic acid (I) is described. © 1969, CSIRO. All rights reserved.