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Type: Artigo de periódico
Title: Unexpected synthesis of conformationally restricted analogues of gamma-amino butyric acid (GABA): Mechanism elucidation by electrospray ionization mass spectrometry
Author: Ferraz, HMC
Pereira, FLC
Goncalo, ERS
Santos, LS
Eberlin, MN
Abstract: From previous results with lower homologues, dehydroiodination of the three alkenyl-beta-enamino esters 3a-c was expected to provide six-membered N-heterocyclic products. The reactions of 3a-c with triethylamine are found to lead, however, to the unexpected stereoselective synthesis of the trisubstituted cyclopentane derivatives 4a-c, as confirmed by IR and NMR spectroscopy. Cyclopentanes 4a-c bear two chiral centers and a gamma-amino ester moiety, and are therefore conformationally restricted analogues of gamma-amino butyric acid (GABA), which is the major inhibitory neurotransmitter in the central nervous system. Use of electrospray ionization mass (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) allowed the key iminium ion intermediates 5a-c(+), as well as the protonated molecules of both the reactant and final products, [3a-c + H](+) and [4a-c + H](+), to be intercepted and structurally characterized. From these findings a mechanism for this unexpected but synthetically attractive and efficient stereoselective reaction is proposed.
Country: EUA
Editor: Amer Chemical Soc
Rights: fechado
Identifier DOI: 10.1021/jo048309e
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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