Asymmetric Cycloetherification by Bifunctional Organocatalyst
作者:Keisuke Asano、Seijiro Matsubara
DOI:10.1055/s-0036-1591592
日期:2018.11
synthesis could be effectively performed via kinetic resolution using ζ-hydroxyenone containing a secondary alcohol moiety using a chiral phosphoric acid catalyst. Attempts to obtain enantiomerically enriched tetrahydrofuran derivatives via an intramolecular oxy-Michael addition reaction of ε-hydroxyenone is discussed. Despite previous difficulties associated with the asymmetric induction of this reaction
We report an asymmetric oxy-Michael addition to a γ-hydroxy-α,β-unsaturated thioester via hemiacetal intermediates in the presence of Cinchona-alkaloid-thiourea-based bifunctional organocatalysts. This method provides a novel enantioselective route to β-hydroxy carboxyl compounds, which in turn can be used to synthesize valuable chiral building blocks.
Chiral spiroketal skeletons are found as core structures in a range of bioactive compounds. These natural compounds and their analogues have attracted much attention in the field of drug discovery. However, methods for their enantioselective construction are limited, and easily available optically active spiroketals are rare. We demonstrate a novel catalytic asymmetric synthesis of spiroketal compounds
Catalytic Asymmetric Synthesis of α,β-Disubstituted α,γ-Diaminophosphonic Acid Precursors by Michael Addition of α-Substituted Nitrophosphonates to Nitroolefins
various nitroolefins are shown to proceed with high diastereo- and enantioselectivity when catalyzed by a quinine-derived thiourea-tertiary amine bifunctional catalyst and generate α,γ-diaminophosphonic acidprecursors with contiguous quaternary and tertiary stereocenters.
A directvinylogousMichael reaction of gamma-substituted deconjugated butenolides with nitroolefins has been developed with the help of a newly identified quinine-derived bifunctional catalyst, allowing the synthesis of densely functionalized products with contiguous quaternary and tertiary stereocenters in excellent yield with perfect diastereoselectivity (>20:1 dr) and high enantioselectivity (up