A stereoselective synthesis of the JKLM ring fragment has been  achieved through a coupling between two segments via heteroconjugate  addition, seven-membered ether ring formation mediated by an acetylene  cobalt complex and spiroketalization reaction.
                                    通过异共轭加成、
乙炔钴络合物介导的七元醚环形成和螺酮化反应,两个片段之间的偶联实现了 JKLM 环片段的立体选择性合成。