A facile access to optically active ring C aromatic diterpene derivatives. Highly efficient synthesis of (+)-12-methyl-7-oxopodocarpa-8,11,13-triene-13-carboxylic acid and (+)-13-methyl-7-oxopodocarpa-8,11,13-triene-12-carboxylic acid from manool

Article abstract of DOI:10.1016/0040-4039(95)00665-Y

The extension of our recently developed strategy using the diene 6 as a key intermediate to the synthesis of naturally occurring ring C aromatic diterpene derivatives provided compounds 1a and 2a in five steps from manool 5. However, the physical and spectroscopic properties of either of these synthetic materials did not agree with those reported for margolone, isolated from Azadirachta indica A. Juss. This indicates that the structure 1a assigned to margolone is not correct and it needs to be reinvestigated.