作者:Michael C. McLeod、Zoe E. Wilson、Margaret A. Brimble                                    
                                    
                                        DOI:10.1021/ol202265g
                                    
                                    
                                        日期:2011.10.7
                                    
                                    An enantioselective formal synthesis of berkelic acid is described. The key step Involves a late-stage silyl enol ether addition to a benzannulated oxonium ion with subsequent spiroketalization leading to construction of the tetracyclic core. Thermodynamically controlled equilibration under acidic conditions affords the desired spiroketal configuration as a single diastereoisomer.