Stereocontrolled Synthesis of a C<i><sup>n</sup></i>-C<i><sup>n</sup></i><sup>+6</sup>Building Block for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics from an Epoxy Alcohol by a Reduction/Conjugate Addition/Hydroxylation Sequence
作者:Rainer Kramer、Reinhard Brückner
DOI:10.1002/ejoc.201300182
日期:2013.10
Epoxy alcohol anti-10, derived from a desymmetrizing Sharpless epoxidation (up to 97 % ee) of divinylcarbinol 9, provided the unsaturated 1,3-diol syn-11 upon treatment with RedAl®; syn-11 was converted into the α,β-unsaturated esters (E)- or (Z)-7b in three steps. Cu-promoted 1,4-addition of vinylmagnesium halides to the (E)-ester proceeded with diastereoselectivities of up to 91 % and Cu-catalyzed
环氧醇 anti-10,衍生自二乙烯基甲醇 9 的去对称 Sharpless 环氧化(高达 97% ee),在用 RedAl® 处理后提供不饱和 1,3-二醇 Syn-11;syn-11 在三个步骤中被转化为 α,β-不饱和酯 (E)- 或 (Z)-7b。Cu 促进的乙烯基卤化镁与 (E)-酯的 1,4-加成以高达 91% 的非对映选择性进行,Cu 催化的 1,4-加成以高达 82% 的非对映选择性进行。主要乙烯基化产物syn-22b 的烯醇钾被Davis oxaziridine 羟基化,具有完美但前所未有的非对映选择性。所得羟基酯α,βsyn,β,γsyn-32分三步提供标题化合物的“东部部分”结构单元6。