Synthesis of the Potent Anticancer Agents Ottelione A and Ottelione B in Both Racemic and Natural Optically Pure Forms
                                
                                    
                                        作者:Derrick L. J. Clive、Dazhan Liu                                    
                                    
                                        DOI:10.1021/jo702635t
                                    
                                    
                                        日期:2008.4.1
                                    
                                    The powerful antitumor agents ottelione A and B were synthesized in racemic form by a method that relies on selective ring closing metathesis. Optically pure natural (+)-ottelione A was then made from D-ribose, via an alpha-keto cyclopropane. A key feature of the route is that the cyclopropyl group controls the stereochemistry in the attachment of the ArCH2 unit and is then converted by the action of SmI2 into a vinyl group, so that the substituents on the resulting five-membered ring have the required trans relationship. Epimerization of an intermediate gave access, by the same method to the trans ring fused isomer (-)-ottelione B.