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En el presente trabajo reportamos la síntesis en microescala de la 5,110,15,20-tetrafenilporfirina y de algunos derivados metálicos. Esta técnica resulta factible realizarla en una sesión de enseñanza en el laboratorio de química orgánica heterocíclica de cuatro horas. Los resultados obtenidos son satisfactorios de tal forma que se realiza la síntesis, reactividad y caracterización de compuestos porfírinicos. [ABSTRACT FROM AUTHOR]

Spiroindolines could be synthesized via a very convenient one-pot procedure combining a Ugi coupling and a new copper-catalyzed oxidative process at a peptidyl position. Due to the nature of the first step, this method offers a straightforward access to complex alkaloids with four points of molecular diversity.

Efficient radical cyclization of alkyl iodides to various aromatic systems including pyrrole, indole, isoquinolone, pyridone, and benzene, mediated by dicumyl peroxide, is described. The methodology was used to provide access to 5,6,8,9,10,11-hexahydroindolo[2,1-a]isoquinoline derivatives.

The susceptibility of rats made deficient of taurine by treatment with guanidinoethane sulfonate (GES), to seizures induced by 4-aminopyridine was examined. Guanidinoethane sulfonate, at a concentration of 1% was administered to pregnant rats, in the drinking water 2-3 days prior to delivery and the treatment was continued during nursing. Pups were weaned to the same treatment until 6 weeks of age. This treatment decreased levels of taurine in the cerebral cortex by 70%. 4-Aminopyridine was injected intraperitoneally at doses ranging from 4-7 mg/kg. Taurine-deficient rats showed a greater susceptibility to seizures, as demonstrated by a lowered latency for clonic seizures, an increased incidence of tonic seizures and a higher postseizure mortality. These results suggest an involvement of endogenous taurine in nervous excitability.

4-Aminopyridine (4-AP) stimulated the release of [3H]dopamine from striatal synaptosomes in the rat. At a concentration of 200 microM, 4-aminopyridine increased the spontaneous efflux of dopamine by 170%. The effect of 4-aminopyridine was calcium-dependent, being abolished when calcium was omitted from the incubation medium. Taurine, at a concentration of 25 mM, decreased the stimulatory effect of 4-aminopyridine from 170 to 49%, in the presence of 2.5 mM calcium. When the concentration of calcium in the superfusion medium was reduced to 0.1 mM, taurine had a complete inhibitory effect on the release of [3H]dopamine stimulated by 4-aminopyridine. The effect of taurine was dose-dependent. Glycine had no effect on the release of [3H]dopamine stimulated by 4-aminopyridine, either in the presence of absence of calcium, whereas gamma-aminobutyric acid (GABA) showed a slight inhibitory effect in both conditions. The results suggest that taurine antagonizes the release of [3H]dopamine induced by 4-aminopyridine through an effect mediated by calcium.