Cross-Coupling of Cyclopropanols: Concise Syntheses of Indolizidine 223AB and Congeners

摘要

A new synthetic method for indolizidine or pyrrolizidine alkaloids based on readily available and attractively functionalized cyclopropanols, as exemplified in concise syntheses of indolizidine (-)-223AB, its 3-epimer, (-)-indolizidine 239AB, and (-)-indolizidine 239CD, is reported. This work highlights the applications of S(N)2' alkylation and C-acylation of cyclopropanols to meet stereochemical challenges in natural product synthesis. Also included is diastereoselective cyclization of the resulting aminoallene adduct for bicyclic ring formation.