First Asymmetric Synthesis and Determination of the Absolute Configuration of a Lignan Isolated from Virola sebifera

The first asymmetric synthesis of a lignan isolated from the seeds of Virola sebifera, one of the most widely spread Myristicaceae species in Brazil, in four steps (48 % overall yield) and with excellent stereoselectivity (de, ee ≥ 96 %) is described. The key step is the asymmetric Michael addition of a lithiated enantiopure α‐amino nitrile to an enone, followed by α‐methylation and cleavage of the amino nitrile. The absolute configuration of the naturally occurring 1,4‐diketone was determined by polarimetry as well as by CD spectroscopy and quantum chemical calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)