Chiral synthons from carvone. Part 31.† Enantiospecific total synthesis of (+)-2-pupukeanone and 5-epi-2-pupukeanone
作者:Adusunilli Srikrishna、T. Jagadeeswar Reddy
DOI:10.1039/a802649a
日期:——
The first enantiospecific total synthesis of (+)-2-pupukeanone and 5-epi-2-pupukeanone has been achieved starting from (R)-carvone, employing a radical cyclisation reaction based approach. (R)-Carvone has been transformed into the bicyclo[2.2.2]octenone 12 via kinetic alkylation, bromination of the isopropenyl moiety and intramolecular alkylation, which on further alkylation with prenyl bromide leads
从(R)-香芹酮开始,采用基于自由基环化反应的方法,实现了(+)-2-pupukeanone和5 - epi -2-pupukeanone的第一个对映体特异性全合成。(R)-香芹酮已通过动力学烷基化,异丙烯基部分的溴化和分子内烷基化反应转变为双环[2.2.2]辛烯酮12,再经异戊烯基溴化物进一步烷基化可生成双环[2.2.2]辛烯酮16。 5-外- TRIG从16中获得的溴代醇17的自由基环化提供了异麦芽酮糖19和20的差向异构体混合物以及少量的重排产物21。将异麦芽酮烷19和20转化为烯酮24。或者,用1,4-二溴-2-甲基丁-2-烯将双环[2.2.2]辛烯酮12进行动力学烷基化,然后将5- exo - trig烯丙基进行环烷基化35和选择性官能团转化产生异twistane 23和少量的重排产物29。最后,催化氢化将烯酮24转化为(+)-2-pupukeanone 5和其C-5差向异构体6。