Asymmetric Photodeconjugation: Highly Stereoselective Synthesis of α-Fluorocarboxylic Derivatives
作者:Frédéric Bargiggia、Sylvia Dos Santos、Olivier Piva
DOI:10.1055/s-2002-20028
日期:——
Irradiations of α-fluoro-α,β-unsaturated esters lead to the corresponding α-fluoro-β,γ-unsaturated isomers in good yields. The reaction required the use of an achiral base (typically an amine) to promote the protonation of the photodienolic intermediate. By replacing the ethyl group with a diacetone-d-glucose moiety, the reaction can be carried out in a diastereoselective manner to furnish the deconjugated esters with similar yields and selectivities up to 95%. The adducts were submitted to osmylation conditions to deliver α-fluoro-β-hydroxy-butyrolactones in one single step.
α-氟代-α,β-不饱和酯的辐照导致相应的α-氟代-β,γ-不饱和异构体,产率良好。反应需要使用非手性碱(通常是胺)来促进光二烯醇中间体的质子化。通过用二丙酮-d-葡萄糖部分替换乙基,反应可以以对映选择性方式进行,以提供去共轭酯,产率和选择性高达95%。产物经氧化条件处理,一步生成α-氟代-β-羟基丁内酯。