Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/80342
Type: Artigo de periódico
Title: Reductive decarboxylation of bicyclic prolinic systems. A new approach to the enantioselective synthesis of the Geissman-Waiss lactone. X-ray structure determination of a key lactone intermediate
Author: Ambrosio, JCL
Santos, RHD
Correia, CRD
Abstract: Two concise and enantioselective syntheses of the necine base precursors (1R,5R)-N-Cbz and N-Boc-2-oxa-6-azabicyclo[3.3.0]octan-3-ones (Geissman-Waiss lactones) were carried out from two enantiomerically pure endocyclic five-membered enecarbamates with overall yields of 23% and 26%, respectively. The synthetic strategy made use of a highly effective and stereoselective [2+2] cycloaddition of enantiomerically pure endocyclic enecarbamates with dichloroketene, as well as an efficient decarboxylation step of a bicyclic alpha-amino acid employing Boger's acyl selenide protocol employing tributyltin hydride. Interesting aspects concerning the regiochemical outcome of Baeyer-Villiger oxidations of bicyclic cyclobutanones are also reported, in which the usual stereoelectronic bias of Baeyer-Villiger oxidation seems to be counterbalanced by steric effects on the putative Criegee intermediate.
Subject: Geissman-Waiss lactone
[2+2]cycloadditions
decarboxylation
pyrrolizidine alkaloids
Country: Brasil
Editor: Soc Brasileira Quimica
Rights: aberto
Date Issue: 2003
Appears in Collections:Unicamp - Artigos e Outros Documentos

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