The total syntheses of (+)-crotanecine, (-)-hastanecine and (-)-rosmarinecine utilizing the tandem (4+2)/(3+2) cycloadditions of nitroalkenes
type: CreativeWork
description: A short and efficient asymmetric synthesis of the pyrrolizidine necine base (${-}$)-hastanecine is described. The key reaction in the synthesis is a sequential inter (4+2) /inter (3+2) cycloaddition. The Lewis acid promoted (4+2) cycloaddition between 2-acyloxy nitroalkene 90 and chiral vinyl ether (+)-28 afforded a nitronate which underwent facile (3+2) cycloaddition with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.
abstract: A short and efficient asymmetric synthesis of the pyrrolizidine necine base (${-}$)-hastanecine is described. The key reaction in the synthesis is a sequential inter (4+2) /inter (3+2) cycloaddition. The Lewis acid promoted (4+2) cycloaddition between 2-acyloxy nitroalkene 90 and chiral vinyl ether (+)-28 afforded a nitronate which underwent facile (3+2) cycloaddition with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.
author: Thorarensen, Atli
language: eng
keywords: Chemistry, Organic
date published: 2011-05-07T12:24:17Z
date modified: 2026-07-22T22:25:15Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/19961