Divergent Asymmetric Total Synthesis of (−)‐Voacafricines A and B

A divergent asymmetric total synthesis of voacafricines and B, hexacyclic monoterpene indole alkaloids, has been accomplished featuring the following key steps: a) a catalyst-controlled Pictet–Spengler reaction 6-methoxytryptamine with chiral α-ketoester affording 1,1-disubstituted tetrahydro-β-carboline in excellent yield diastereoselectivity; b) oxidative cleavage 3,5-disubstituted cyclopentene furnishing dialdehyde intermediate, which was effectively differentiated through spontaneous cyclization neighboring hydroxy secondary amine functions; c) intramolecular nucleophilic addition tertiary amino nitrogen atom to situ generated oxonium species generating stereoselectively an unprecedented 8-alkyl octahydro-2H-5,8-methanofuro[2,3-b]azepin-8-ium motif bearing five contiguous stereocenters. The confirmed absolute configuration these two natural products.