Stereocontrolled synthesis of the AB rings of samaderine C.

A concise synthesis of the AB rings of samaderine C (12 steps, 8 isolation steps, 7.8% overall yield), a quassinoid with antifeedant and insecticidal activity, is described. The development of the first general approach to the trans-1,2-diol A-ring motif in samaderine C and other quassinoids is a key feature. The trans-1,2-diol is crafted via stereoselective α-hydroxylation (of a silyl enol ether) and reduction, a strategy that has much potential for quassinoid synthesis.