Ir-catalysed allylicalkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 87% retention of configuration using P(OPh)3 as ligand. High regio- and enantioselectivity of up to 86% ee in asymmetric allylicalkylations of achiral or racemic substrates is achieved with monodentate phosphorus amidites as ligands. Lithium N-tosylbenzylamide was identified as a suitable
使用 P(OPh)3 作为配体,Ir 催化的烯丙基烷基化对映体富集的单取代烯丙基乙酸酯的构型保留率高达 87%。以单齿磷酰胺作为配体,在非手性或外消旋底物的不对称烯丙基烷基化中实现了高达 86% ee 的高区域和对映选择性。N-tosylbenzylamide 锂被确定为适合烯丙基胺化的亲核试剂。特别重要的是使用氯化锂作为添加剂,通常会导致对映选择性增加。通过 X 射线晶体结构分析和光谱数据对两种 (π-烯丙基) IrIII 配合物进行了表征。
Remarkable Ligand Effects in Regioselective Palladium-Catalysed Allylic Substitution Reactions
The use of tricyclohexylphosphine (and related phosphines) in palladium-catalysedallylicsubstitution reactions enables the selective conversion of branched allylic acetates into the branched substitution products (up to 120:1 regioselectivity). Linear allylic acetates do not show the same selectivity for the branched substitution products, thereby demonstrating a memory effect.
Synthesis and Glycosidase Inhibition Studies of 5-Methyl-Substituted Tetrahydroxyindolizidines and -pyrrolizidines Related to Natural Hyacinthacines B
作者:Daniele Martella、Francesca Cardona、Camilla Parmeggiani、Francisco Franco、Juan A. Tamayo、Inmaculada Robina、Elena Moreno-Clavijo、Antonio J. Moreno-Vargas、Andrea Goti
DOI:10.1002/ejoc.201300103
日期:2013.7
The synthesis of three tetrahydroxyindolizidines and one tetrahydroxypyrrolizidine related to natural hyacinthacines B and their biological evaluation as glycosidase inhibitors is reported. The target molecules were obtained through highly stereoselective cycloadditions between sugriched allylic and homoallylic alcohols. This allowed the installation of a methyl group at C5 – a common feature of many
报道了与天然风信子 B 相关的三种四羟基吲哚里西啶和一种四羟基吡咯里西啶的合成及其作为糖苷酶抑制剂的生物学评价。目标分子是通过糖化烯丙醇和高烯丙醇之间的高度立体选择性环加成获得的。这允许在 C5 上安装一个甲基——这是许多天然风信子的一个共同特征——对立体选择性的高度控制。新化合物抑制来自黑曲霉的淀粉葡萄糖苷酶和来自杏仁的β-葡萄糖苷酶。化合物 1 是淀粉葡萄糖苷酶的竞争性抑制剂,对这种酶表现出相当的选择性。