A Diastereoselective Cyclic Imine Cycloaddition Strategy To Access Polyhydroxylated Indolizidine Skeleton: Concise Syntheses of (+)-/(−)-Lentiginosines and (−)-2-epi-Steviamine
摘要:
We describe in this paper the development of a novel diastereoselective cyclic imine cycloaddition strategy to access the polyhydroxylated indolizidine skeleton and its application in the concise syntheses of (+)-/(-)-lentiginosines and (-)-2-epi-steviamine.
A direct approach to the synthesis of indolizidine and quinolizidine scaffolds of iminosugars is described. The presented strategy is based on a one-pot sugar lactam reduction with Schwartz’s reagent followed by a diastereoselective Mannich/Michael tandem reaction of the resulting sugar imine with Danishefsky’s diene. The stereochemical course of the investigated reaction has been explained in detail