Progress toward the total synthesis of vannusal A

Vannusal A and B are two natural products isolated from the ciliate Euplotes vannus. These secondary metabolites are complex triterpenes that have an unusual and highly crowded carbon framework. Progress toward the synthesis of vannusal A is described, along with a methodology developed to access a key building block in high enantiomeric excess.; The scope and limitations of a catalytic asymmetric three-component 1,4-addition/aldol reaction of enones, aldehydes and alkenyl zirconium species is described as well as the preparation of enantiomerically enriched 2,3-disubstituted aldols and enones.