Related Experiment Video
Updated: Aug 9, 2025

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
Published on: June 13, 2022
Divergent Asymmetric Total Synthesis of (-)-Voacafricines A and B
Rémi Andres1, Qian Wang1, Jieping Zhu1
1Laboratory of Synthesis and Natural Products (LSPN), Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304 1015, Lausanne, Switzerland.
Abstract:
A divergent asymmetric total synthesis of voacafricines A and B, hexacyclic monoterpene indole alkaloids, has been accomplished featuring the following key steps: a) a catalyst-controlled asymmetric Pictet-Spengler reaction of 6-methoxytryptamine with a chiral α-ketoester affording a 1,1-disubstituted tetrahydro-β-carboline in excellent yield and diastereoselectivity; b) oxidative cleavage of a 3,5-disubstituted cyclopentene furnishing a dialdehyde intermediate, which was effectively differentiated through spontaneous cyclization with the neighboring hydroxy and secondary amine functions; c) intramolecular nucleophilic addition of a tertiary amino nitrogen atom to the in 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 synthesis confirmed the absolute configuration of these two natural products.
Related Concept Videos
Stereoisomerism of Cyclic Compounds
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
Prochirality

