An asymmetric synthesis of aza analogues of the ABC ring system of phorbol and related compounds containing the 5-7-6-fused framework of daphnane involved construction of the central seven-membered ring by a regioselective reduction of a chiral imide and cyclization with trifluoromethanesulfonic acid. Subsequent demethylation and oxidative dearomatization of ring C afforded an enantiopure dienone 20 with the same relative and absolute configuration at the 9- and 10-positions of the phorbol skeleton.
