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Paper | Regular issue | Vol 68, No. 8, 2006, pp.1631-1649
Published online, 8th June, 2006
DOI: 10.3987/COM-06-10776
Synthesis and Structural Study of Semicarbazone-Containing 1,4-Dihydropyridine

Amaury Álvarez, Margarita Suárez,* Yamila Verdecia, Estael Ochoa, Blavet Barried, Rolando Pérez, Mercedes Díaz, Roberto Martínez-Álvarez, Dolores Molero, Carlos Seoane, Hector Novoa, Norbert M. Blaton, Oswald M. Peetersd, and Nazario Martín*

*Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain

Abstract

A new series of 1,4-dihydropyridines (1,4-DHPs) bearing a semicarbazone moiety on C5 (8a-g) have been synthesized from suitably functionalized 1,4-DHPs (2) and semicarbazide. Compounds (8a-g) did not cyclize to the respective seven member ring though this is a favoured 7-endo-trig process. Geometrical and structural features determined by theoretical, DFT (B3LYP/6-31G*) and experimental (X-Ray diffraction) data, reveal the presence of a low energy stereoisomer, namely (E) s-trans, which is also present in solution according to NOe experiments carried out on compound (8a). These geometrical findings account for the lack of cyclization of compounds (8a-g), and reveal that they meet the structural requirements needed for biological activity as calcium-channel modulators.