Total synthesis of indole alkaloid (+/-)-subincanadine F via SmI2)-mediated ring opening and bridge-forming Mannich reaction

The first total synthesis of (+/-)-subincanadine F, a bioactive indole alkaloid structurally featuring a 1-azabicyclo4.3.1]decane unit, has been realized from 1-(para-methoxybenzyl)tryptamine in six steps. The bridge-containing tetracyclic framework of subincanadine F was efficiently assembled by a SmI2-mediated ring opening followed by an acid-mediated Mannich reaction. In addition, the tetracyclic ketoester 6, a key intermediate potentially useful for synthesizing structurally related indole alkaloids as well, was obtained in one step from alpha,beta-diketoester 5.