A divergent approach for the total syntheses of cernuane-type and quinolizidine-type Lycopodium alkaloids

The divergent total syntheses of cernuane-type and quinolizidine-type Lycopodium alkaloids are described. A common intermediate 5 for the two types of alkaloids was assembled practically from (+)-citronellal via organocatalytic alpha-amination, followed by the construction of oxazolidinone that was used for diastereciselective allylation. Key compound 5 was converted into cermizine C (3), and this in turn was converted into senepodine G (4) by the regioselective Polonovsky-Potier reaction. The total synthesis of representative cernuane-type alkaloids, (-)-cernuine (1) as well as (+)-cermizine D (2), was also accomplished from 5 by utilizing asymmetric transfer aminoallylation as a key step. (C) 2008 Elsevier Ltd. All rights reserved.