Organocatalyzed Cyclopropanation of α-Substituted α,β-Unsaturated Aldehydes: Enantioselective Synthesis of Cyclopropanes Bearing a Chiral Quaternary Center
作者:Vincent Terrasson、Arie van der Lee、Renata Marcia de Figueiredo、Jean Marc Campagne
DOI:10.1002/chem.201000334
日期:——
An enantioselective cyclopropanation of α‐substituted α,β‐unsaturated aldehydes with bromomalonate has been successfully developed through a dominoMichael/α‐alkylation strategy. The method allows the efficient formation of cyclopropanes bearing a quaternary carbon stereocenter at the α‐position of the aldehydes by using iminium/enamine catalysis and gives a nice extension on the organocatalytic cyclopropanation
allows regio- and stereocontrolled access to a variety of functionalised and substituted seven-membered rings. The substitution array can be diastereoselectively modulated by appropriate choice of the reaction partners, and the reaction allows the control of up to five newly created stereocentres and a complete chiral induction in the case of an opticallyactive ketone precursor. The high level of
Synthesis of the Pentacyclic Framework of the Alkaloid Tronocarpine
作者:Rubén O. Torres-Ochoa、Paul E. Reyes-Gutiérrez、Roberto Martínez
DOI:10.1002/ejoc.201301388
日期:2014.1
A short and efficient synthesis of the pentacyclic core of the indole alkaloid tronocarpine is described. The synthetic pathway involves several easily accomplished steps, including a radical oxidative aromatic substitution reaction on the N-tertbutoxycarbonyl-protected tryptamine and a xanthate, a 1,4–