A Four-Step Route from Aldehydes to C<sub>2</sub>-Elongated Enantiomerically Pure <i>α</i>,<i>β</i>-Unsaturated <i>γ</i>-Hydroxy Esters
作者:Christian Harcken、Reinhard Brückner
DOI:10.1055/s-2001-13372
日期:——
Asymmetric dihydroxylation of β,γ-unsaturated esters 4 provided β-hydroxy-γ-lactones 3 or ent-3. Methanolysis acetonide formation and LDA-mediated fragmentation of the resulting esters 5/ent-5 furnished the γ-chiral acrylates 6/ent-6 containing disubstituted C=C bonds (93-99% ee). Also, β-hydroxy-γ-lactones ent-3 a and 3 b were α-butylated and α-brominated, respectively, prior to methanolysis, acetonide formation, and fragmentation which led to the γ-chiral acrylates 9 and 12 with trisubstituted C=C bonds (94 and 95% ee, respectively).
β,γ-不饱和酯4 的不对称二羟基化提供β-羟基-γ-内酯3 或ent-3。甲醇分解丙酮化物的形成和所得酯5/ent-5 的LDA 介导的断裂提供了含有双取代C=C 键(93-99% ee)的γ-手性丙烯酸酯6/ent-6。此外,β-羟基-γ-内酯 ent-3 a 和 3 b 分别在甲醇解、丙酮化物形成和裂解之前进行 α-丁基化和 α-溴化,从而产生 γ-手性丙烯酸酯 9 和 12三取代的 C=C 键(分别为 94% 和 95% ee)。