A synthesis of (−)-tashiromine and formal synthesis of (+)-tashiromine utilizing a highly enantioselective pyrrole/cobaloxime π-cation cyclization
                                
                                    
                                        作者:Jennifer L Gage、Bruce P Branchaud                                    
                                    
                                        DOI:10.1016/s0040-4039(97)01638-9
                                    
                                    
                                        日期:1997.10
                                    
                                    Cyclization of (5-N-pyrrolyl-2-hydroxypentyl)cobaloxime (13) proceeds by intramolecular electrophilic aromatic substitution of a cobaloxime pi-cation onto the pyrrole ring to provide 6-exo cyclization product (14) in 95% yield. This cyclization is highly enantioselective. It is applied to a synthesis of highly enantioenriched (-)-tashiromine, (-)-21, and a formal synthesis of (+)-tashiromine. (C) 1997 Elsevier Science Ltd.