Stereoselective Preparation of (E)-Configured 1,2-Disubstituted Propenes from Two Aldehydes by a Two-Carbon Stitching Strategy: Convergent Synthesis of 18,21-Diisopropyl-Geldanamycin Hydroquinone and Its C7 Epimer
作者:Thomas Hampel、Thomas Neubauer、Thomas van Leeuwen、Thorsten Bach
DOI:10.1002/chem.201201600
日期:2012.8.13
The assembly of the two aldehydes was achieved employing α‐chloroethyl magnesium chloride as a two‐carbon building block. The carbenoid reagent was generated from α‐chloroethyl para‐tolylsulfoxide by sulfoxide–magnesium exchange and it added smoothly to the highly sensitive aldehyde of the Eastern fragment (C1C7). Upon oxidation, an α‐chloroethyl ketone was generated, which underwent a clean and high‐yielding
标题化合物以27个线性步骤的最长序列合成,总产率为2.9%和3.9%。在合成的过程中,表示碳碎片C1两种醛 C7(东部片段)和C9 从制备C21(西片段)d -mannitol,其中的每一个在相应的次级甲基醚基团结合的关键手性中心( C6,C12)。这两种醛的组装是通过使用α-氯乙基氯化镁作为双碳结构单元来实现的。类胡萝卜素试剂是由α-氯乙基对甲苯基亚砜通过亚砜与镁的交换而生成的,并平滑地添加到东部片段的高度敏感的醛中(C1C7)。氧化后,生成α-氯乙基酮,该酮经历了干净且高产的还原性SmI 2。-促进了其他醛片段的添加。脱水通过四个步骤在C8和C9之间提供了关键的双键,总收率为72%。结果表明,该方法通常适用于多种醛的无消旋转化为相应的α-氯乙基酮(11个实例,占64-95%)和偶联方案(5个实例,占66-90%)。格尔德霉素对苯二酚合成的进一步过程包括C7处的非对映选择性还原和C