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(Reference retrieved automatically from SciELO through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

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

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Author(s):
João Carlos L. Ambrósio [1] ; Regina Helena de A. Santos [2] ; Carlos R. D. Correia [3]
Total Authors: 3
Affiliation:
[1] Universidade Estadual de Campinas. Instituto de Química - Brasil
[2] Universidade de São Paulo. Instituto de Química de São Carlos - Brasil
[3] Universidade Estadual de Campinas. Instituto de Química - Brasil
Total Affiliations: 3
Document type: Journal article
Source: Journal of the Brazilian Chemical Society; v. 14, n. 1, p. 27-38, 2003-01-00.
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. (AU)