Two approaches for the synthesis of ring-A-oxygenated diterpenes are described. Several routes from natural podocarpic acid aimed at the synthesis of coleon E afforded a wide range of potentially useful chiral derivatives, but the other scheme, which involved a cascade-type cyclization, led to the synthesis of the O-methyl ether of (±)-margocilin [33c] (recently isolated from Azadirachta indica).

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The structure of margocin {24] is confirmed by its synthesis from useful synthons encountered during transformations exploring the utility of dehydroabietic acid as a chiral starting material for natural product synthesis.