Asymmetric and ?anti?-Selective Aldolisations of Acetates and Propionates. Preliminary Communication
作者:Wolfgang Oppolzer、Jos� Marco-Contelles
DOI:10.1002/hlca.19860690725
日期:1986.10.29
Starting from acetates 1 and propionates 6, TiCl4-mediated addition of their silyketene acetals 2 and 7 to aldehydes gave aldols 4 and 9, respectively, with high π-face and ‘anti’ differentiation (Schemes, and Tables 1 and 2). Alternation of the (E/Z)-enolate geometry led to reversed α- and β-inductions (7 9b, 8 10b). Non-destructive removal of the auxiliary yielded enantiomerically pure β -hydroxycarboxylic
1,3-Dioxan-4-ones 6and 7 derived from (–)-menthone can be utilized in resolution of 3-hydroxycarboxylic acids and asymmetric synthesis of 2-substituted 3-hydroxycarboxylic acids.
Chemical Synthesis of a Glycolipid Library by a Solid-Phase Strategy Allows Elucidation of the Structural Specificity of Immunostimulation by Rhamnolipids
variations in the carbohydrate part, the lipid components, and the stereochemistry of the 3-hydroxy fattyacids was designed and synthesized. The enantioselective synthesis of the 3-hydroxy fattyacid building blocks was achieved by employing asymmetric hydrogenation of 3-oxo fattyacids. Glycolipids were prepared by this approach without any intermediary isolation steps, mostly in excellent yields. Final