A Convenient Access to (All-<i>rac</i>)-α-Tocopherol Acetate from Linalool and Dihydromyrcene
作者:Vincent Gembus、Nathalie Sala-Jung、Daniel Uguen
DOI:10.1246/bcsj.82.829
日期:2009.7.15
Refluxing trimethylhydroquinone 2 in 10:1 dodecane/CH2Cl2 with linalool 3b (two-fold excess) and camphorsulfonic acid, then treating the crude condensation product (consisting of a mixture of the chromanols 1b and 1c, alongside the tricyclic compounds 9 and 10) sequentially with Ac2O and m-CPBA afforded, after removal by column chromatography of the 9/10 acetates, a mixture of the regioisomeric epoxides 1jOAc and 1kOAc (ratio 9:1, total 60%). Treatment of this mixture with Al(O-i-Pr)3 followed by CuI-catalysed Wurtz coupling of the acetates of the resulting allylic alcohols with citronellylmagnesium chloride 12a, and finally hydrogenation then provided the title acetate (overall 46% from 2).
将三甲基氢醌 2 在 10:1 的十二烷/二氯甲烷中与过量的香叶醇 3b 和樟脑磺酸催化剂重流,随后对粗凝聚物(由克罗曼醇 1b 和 1c 以及三环化合物 9 和 10 的混合物组成)依次用醋酸酐和对氯苯甲酸酯处理,经过柱层析去除 9/10 乙酸酯后,得到区域异构体环氧化物 1jOAc 和 1kOAc 的混合物(比例为 9:1,总产率 60%)。将该混合物与 Al(O-i-Pr)3 处理,然后用 CuI 催化的沃尔茨偶联反应将得到的烯醇乙酸酯与香柠檬醇镁氯化物 12a 偶联,最后进行氢化,便得到标题乙酸酯(总体产率为 46%)。