Total Synthesis of Both Enantiomers of Copalol via Optical Resolution of a General Synthetic Intermediate for Drimane Sesquiterpenes and Labdane Diterpenes
作者:Hiroaki Toshima、Hideaki Oikawa、Tomonobu Toyomasu、Takeshi Sassa
DOI:10.1016/s0040-4020(00)00791-2
日期:2000.10
The total synthesis of both enantiomers of copalol (6) was accomplished via the optical resolution of a racemic diol [(±)-4] which is a general synthetic intermediate for drimane sesquiterpenes and labdane diterpenes. Esterification between (±)-4 and Boc-l-proline gave the diastereomeric pair of monoesters (5a and 5b) which could be readily separated by flash column chromatography. PDC-oxidation of
Copalol(6)的两个对映异构体的总合成是通过消旋二醇[(±)-4 ]的旋光拆分完成的,该消旋二醇是drimane倍半萜和拉丹烷二萜的通用合成中间体。(±)-4和Boc-1-脯氨酸之间的酯化反应得到非对映体的单酯对(5a和5b),可以通过快速柱色谱法轻松分离。拆分的5a和5b进行PDC氧化,然后进行β消除,得到旋光的烯酮(9和ent -9)。两种烯酮分别以36%的收率和(-)-转化为(+)- 6在以下五个步骤中以26%的产率获得6:(1)Sakurai反应(TiCl 4促进烯丙基硅烷的共轭加成),(2)Wittig亚甲基化,(3)Wacker氧化,(4)Horner-Emmons反应和(5)DIBAL -H减少。