Total Synthesis of (2<i>RS</i>)-α-Tocopherol through Ni-Catalyzed 1,4-Addition to a Chromenone Intermediate
作者:Andreas Ole Termath、Janna Velder、René T. Stemmler、Thomas Netscher、Werner Bonrath、Hans-Günther Schmalz
DOI:10.1002/ejoc.201402240
日期:2014.6
A novel strategy for the total synthesis of α-tocopherol (“vitamin E”) was elaborated on the basis of the conjugate addition of AlMe3 (as a methyl anion equivalent) to a 2-substituted chromenone. Starting from trimethylhydroquinone and (R,R)-hexahydrofarnesol, the required chromenone substrate was efficiently prepared in a short sequence exploiting a TiCl4-mediated Fries rearrangement and a KOtBu-induced
α-生育酚(“维生素 E”)全合成的新策略是基于 AlMe3(作为甲基阴离子等价物)与 2-取代色酮的共轭加成。从三甲基氢醌和 (R,R)-六氢法呢醇开始,利用 TiCl4 介导的 Fries 重排和 KOtBu 诱导的 Baker-Venkatamaran 重排,在短序列中有效地制备了所需的色酮底物。设想的关键步骤是在 C2 处建立四元中心,通过 Ni 催化的 AlMe3 共轭加成以几乎定量的收率进行。然而,这种可能通过自由基机制进行的转化无法通过手性配体实现立体选择性。然而,(2RS,4'R,