Guido Settimj

Proton and carbon nuclear magnetic resonance study on some n- and o-acyl derivatives of monohydroxypyridines☆

Abstract Comparative study on the proton and carbon NMR spectra for a series of N - and O -acyl substituted monohydroxypyridines (C5H4NO R : R =-H, -CHO, -COCH3, -COC(CH3)3, -COCF3, -COC6H5, -SO2CH3, -SO2C6H4CH3 is reported. p]Characteristic 1H, 13 NMR and IR spectral features allow simple and unambiguous distinction between the isomeric N - and/or O -acyl-derivatives of 2-, 3- and 4-hydroxypyridines, so that both forms can clearly be identified when tautomeric equilibria occur, since the tautomerism rate is slow on the NMR time scale

A new gas chromatographic method for the estimation of reserpine and rescinnamine

Under the conditions described for alkaline hydrolysis of reserpine and rescinnamine in absolute and aqueous methanol, and after esterification (with diazomethane) of the resulting acid fraction, methyl 3,4,5-trimethoxybenzoate was quantitatively recovered, whereas methyl trans-3,4,5-trimethoxycinnamate, in normal lighting conditions, was either partly isomerized to methyl cis-trimethoxycinnamate or formed an adduct with a molecule of methanol, yielding methyl 3-methoxy-3-(3,4,5-trimethoxyphenyl)propionate. The structures of the products were established by synthesis, nuclear magnetic resonance studies and mass spectrometry. This investigation of the hydrolytic conditions allowed a reliable and rapid gas chromatographic determination of reserpine and/or rescinnamine in amounts down to 500 and 2000 mug, respectively, to be devised.

Application of a high-performance liquid chromatography coulometric method for the estimation of mebendazole and its metabolites in human sera

A novel, sensitive high-performance liquid chromatographic method, making use of coulometric detection, for the estimation of mebendazole and its metabolites in the sera of eight hydatidosis patients was devised. Recovery rates, precision, accuracy and sensitivity for each compound are reported and compared with those of the previously published methods.

Charge-transfer interactions in some 2-, 3-, 4-substituted N-methylpyridinium iodides and tri-iodides

Abstract The charge transfer (CT) interactions involving the substituted pyridinium ion are of a remarkable biological interest. In particular the pyridinium ions having substituents in position 3 of the heterocyclic ring constitute models for the study of similar, more complex structures. In this paper some spectral characteristics are reported which show such CT interactions between N-methyl-2-, -3-, -4-metoxypyridinium ions and iodide ions, and between N-methyl-2-, -3-, -4-tiomethylpyridinium ions and iodide and tri-iodide ions. The pyridinium ions substituted in position 3 turned out to be the strongest electron-acceptors. The 1H N.M.R. investigations concerning the N+-CH2 chemical shift confirmed that : I. a substituent of the -OCH3 and -SCH3 type in the pyridine ring causes a rise in the negative charge on the nitrogen in relation to the position in the ring according to the sequence 2 > 4 > 3 ; 2. the substitution of the -O-CH3 group with the -S-CH3 group seems to modify the nitrogen charge-density only when the substitution takes place in position 2.

β-Carbolines as inverse agonistic benzodiazepine receptor ligands. 2. Synthesis and in vitro and in vivo binding of some new 6-amino- and 6-fluoro-β-carboline-3-carboxylates

Summary Six new 6-fluoro-β-carboline-3-carboxylates ( 3a–f ) with their related 6-amino analogues ( 2a–f ) are described and their in vitro and in vivo capabilities to bind to rat cerebral cortex ‘benzodiazepine receptors’ checked by radioreceptor assay (RRA). For some of the derivatives, the tests were also accomplished in the absence and presence of 10 μM GABA, whereby an inverse agonistic activity resulted. Their IC 50 for [ 3 H]flunitrazepam displacement were in the 10 −9 –10 −12 molar range. The same compounds, with the exception of the hydroxylated compounds 2e, 2f, 3e and 3f , crossed the blood—brain barrier in the rat, generally giving rise to higher concentrations in the brain (ng/g) than in the plasma (ng/ml). The synthetic pathway preferred here allows a rapid fluorine incorporation in this moiety and an easy isolation of the fluorinated compounds.

13C- and 1H-NMR relaxation investigation of a polyciclic nitrogen compound: 3,3-dimethyl-1,5-diphenyl-9-hydroxy-bispidinium iodide

Abstract The rigid polycyclic nitrogen compound was considered as a test for the reliability of internuclear distances calculated by 1H-NMR spin-lattice relaxation rates. The ‘isotropic’ motional correlation time was calculated from 13C relaxation rates (τC = 0.11 ns at 298 K). Dipolar cross-relaxation rates were calculated by measuring non-, mono- and double-selective proton spin-lattice relaxation rates. All the experimental relaxation rates were thoroughly accounted for by dipolar pairwise interactions. Only at high temperatures a certain contribution from the spin rotational mechanism was apparent.