Stereo- and Regioselective Synthesis of Squalene Tetraepoxide
作者:Rongbiao Tong、Matthew A. Boone、Frank E. McDonald
DOI:10.1021/jo901920d
日期:2009.11.6
Squalene tetraepoxide, it putative biosyntheic precursor to a variety of oxacyclic triterpenoid natural products, has been efficiently synthesized by anionic coupling of two farnesol-derived diepoxides, which have arisen from electronic control of the regioselectivity in organocatalytic enantioselective epoxidations.
Synthetic Access to Bent Polycycles by Cation-π Cyclization
作者:Ryan A. Shenvi、E. J. Corey
DOI:10.1021/ol101410g
日期:2010.8.6
The presence of an ether oxygen within a chain undergoing cation-polyene cyclization has a profound Influence on the stereochemistry of this important construction, apparently due to nucleophilic participation of oxygen in the cyclization process and formation of an oxonium intermediate, leading to bent fused ring systems.