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Type: Artigo de periódico
Title: Unexpected Synthesis Of Conformationally Restricted Analogues Of γ-amino Butyric Acid (gaba): Mechanism Elucidation By Electrospray Ionization Mass Spectrometry
Author: Ferraz H.M.C.
Pereira F.L.C.
Goncalo E.R.S.
Santos L.S.
Eberlin M.N.
Abstract: (Chemical Equation Presented). From previous results with lower homologues, dehydroiodination of the three alkenyl-β-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 γ-amino ester moiety, and are therefore conformationally restricted analogues of γ-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.
Rights: fechado
Identifier DOI: 10.1021/jo048309e
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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