β-enamine esters as precursors of GABA and dihydropyridines analogues / bβ-enamino ésteres como precursores de análogos do GABA e de di-hidropiridinas

AUTOR(ES)

Erika Rocha da Silva Gonçalo

DATA DE PUBLICAÇÃO

2006

RESUMO

This thesis presents a study of iodo-cyclization of β-enamino esters in order to obtain conformationally restricted analogues of γ-amino butiric acid (GABA) and of 1,4-dihydropyridines (DHPs). Trisubstituted cyclopentanes were obtained from iodo-β-enamino esters and the mechanism of their formation was proposed and corroborated by (+)-ESI-MS/MS through the interception and structural characterization of the key bicyclic iminium ion intermediates. Optically active GABA analogues have been prepared in high enantiomeric excesses (up to >99%) by bioreduction of the keto group in cyclopentane derivatives using whole fungal cells of Aspergillus terreus CCT 3320, Rhizopus oryzae CCT 4964 and Daucus carota root. 4-aryl-1,4,5,6-tetrahydropyridine derivatives were synthesized by iodo-cyclization of a-alkenyl-b-enamino esters and 4-phenyl-1,4-dihydropyridine derivatives were obtained after base-promoted dehydroiodination of the corresponding cyclic iodo-b-enamino esters.

ASSUNTO(S)

gaba dihydropyridines gaba iodocyclization enamine esters di-hidropiridinas iodociclização enamino ésteres

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