Position Of Nitrogen Atom Research Articles

Mass spectra of azastilbenes

Mass spectra of twelve azastilbenes (eight diazastilbenes, DAS , and four triazastilbenes, TAS are reported and compared with previous results for stilbene, monoazastilbenes ( MAS ) and DAS. Stable molecular ions M ⨥ are characteristic for all spectra. The fragmentation pathways were traced and confirmed by metastable transition measurements in the first and second field free region and by exact mass determinations. The fragmentation of DAS and TAS is highly dependent on the mutual positions of nitrogen atoms.

Polarographic study of flurazepam and its major metabolites

The polarographic behaviours of flurazepam, N-1-hydroxyethylflurazepam, flurazepam-N-1-acetic acid, N-1-desalkylflurazepam and N-1-desalkyl-3-hydroxyflurazepam have been systematically studied over the pH range 0–14. Values for pK1 and pK3, obtained from a study of E½versus pH and i1im.versus pH relationships, corresponding to protonation of the azomethine group and deprotonation of the hydrogen ion attached to the nitrogen atom in position I, respectively, have been determined and are in agreement with those obtained by more accurate spectrophotometric methods. Values of pK2 corresponding to protonation of the nitrogen atom in the diethylamino side-chain in the first of the above compounds, the carboxylic acid function in the third and the 3-hydroxy function in the last, inaccessible by spectrophotometric methods, have been determined polarographically as 9, 4.5 and 5.5, respectively.Linear calibration graphs of ipversus concentration in pH 4 formate buffer were obtained down to 5 × 10–8M using cathode-ray and differential-pulse polargraphy and were linear over a least three orders of magnitude of concentration for flurazepam and the metabolites listed above. Capsules containing 15 and 30 mg of active constituent were assayed by a method involving cathode-ray polarography and relative standard deviations in the range 0.66–2.66% were obtained.

Photoelectron Spectroscopy of Heterocycles 1-(Diazinyl)-2-(Pyridyl)-ethenes (Triazastilbenes)

The photoelectron (PE) spectra of 1-(4-pyrimidyl)-2-(3-pyridyl)-ethene 1, 1-(2-pyrimidyl)-2- (3-pyridyl)-ethene 2, 1-(4-pyridazinyl)-2-(3-pyridyl)-ethene 3, 1-(3-pyridazinyl)-2-(3-pyridyl)- ethene 4 and 1-(2-pyrazinyl)-2-(3-pyridyl)-ethene 5 all in their trans conformations have been recorded using Hel radiation. Comparisons with the PE spectra of styrylpyridines, dipyridylethenes and diazabenzenes allowed the assignment of all ionization energies, Ei, corresponding to π- and nitrogen lone pair ionizations in the region of Ei < 12 eV. The variations in PE spectra of five isomeric triazastilbenes studied are due to different nitrogen atom positions in the diazinyl ring.

In vitro studies on the metabolism of dibenzo[c,f]-[1,2]diazepine.

Dibenzo [c,f]-[1,2] diazepine is a new compound with a tricyclic structure and a double bond between two nitrogen atoms in positions 1 and 2 of the molecule. Its in vitro metabolism has been studied, incubating the compound with rat liver microsomes. Two metabolites have been identified: dibenzo [c,f] - [1,2]diazepine-1-N-oxide and a monohydroxyderivative in the aromatic ring.

A spectral and polarographic study of the acid—base and complexing behaviour of bromazepam

A spectral and polarographic study of bromazepam yielded pK a values of 2.5, 5.2 and 11.8, corresponding to protonation at the azomethine and pyridine nitrogen atoms, and deprotonation at the nitrogen atom in position 1, respectively. These acid-base equilibrium reactions are discussed with reference to the hydrolysis and complexing properties of this compound. An indirect analytical method, based on the complexation of bromazepam with Cu 2+ ions, has been investigated by differential pulse anodic stripping voltammetry.

Etude sur les carbéthoxy-3 pyrazolinones-5: contribution à l'étude des formes tautomériques et préparation de sels d'hydrazinium et de guanidinium

The tautomeric NH-form is preferentially adopted by 3-carbethoxy-5-pyrazolinones in the solid state and in solution; the solvent does not cause a radical change in form because these molecules are quite polar and appear to be stabilized by a rather extended conjugated system and possibly also by chelation of the carbonyl group of the carbethoxy group in position 3 with the hydrogen atom attached to the nitrogen atom in position 2.These 3-carbethoxy-5-pyrazolinones form hydrazinium and guanidinium salts in the presence of hydrazine and guanidine in ethanolic solution by means of a proton transfer.

Speculations about the binding sites of S-adenosyl-L-homocysteine and some of its synthetic analogues to histamine methyltransferase.

None of the synthetic analogues ofS-adenosyl-l-homocysteine was a more potent inhibitor of the enzyme thanS-adenosyl-l-homocysteine itself. Several requirements very probably had to be fulfilled for inhibition of gastric histamine methyltransferase by compounds similar in structure to S-adenosyl-l-homocysteine: (1) The side chain linked to the 5′-position of ribose must bear an amino acid residue; (2) the chain-length of this residue must be the same as that of homocysteine; (3) the heterocyclic base has to be a purine base with a nucleophilic center at position 6; (4) this nucleophilic center must not be sterically hindered by substitutes; (5) the purine base must have a nitrogen atom in position 3. These requirements indicate, that the binding sites, proposed byZappia et al. [2] for various methyltransferases were identical with those found for the fixation ofS-adenosyl-l-homocysteine or its analogues to histamine methyltransferase.

A QUANTUM PHARMACOLOGICAL STUDY ON DIURETICS, XANTHINE, THIAZIDE AND TRIAZINE DERIVATIVES

AbstractThe reaction indices of π-electronic structures of the diuretics, xanthine, thiazide and triazine derivatives were calculated. An attempt was made to explain the potency of the diuretic action in the light of quantum chemistry. The reaction indices of xanthine derivatives, the first frontier superdelocalizability at the substituent occupying the 7-position of the highest occupied orbital and the second frontier superdelocalizability at the 3-position of the occupied orbital show fairly good correlations with the diuretic activities. The reaction index Sr”(E:) is defined as: Sr” = fr1/λ1/fr2/λ2, where subscripts 1 and 2 stand for the highest occupied (or the lowest unoccupied) orbital, and the next highest occupied (or the next lowest unoccupied) orbital, fr is the electron density of the corresponding orbital and λ1 (i=l, 2) is the coefficient of energy in the i-th molecular orbital ε1 = α+λ1, α and β being the standard Coulomb and resonance integrals. The diuretic activities of thiazide derivatives are in good parallel with the reaction indices, the 7r-electron densities at the 2-position, at the 4-position and at the 7-position. The potency of carbonic anhydrase inhibition of thiazide derivatives and sulphonamide derivatives however are fairly well parallel with the reaction indices, the π-electron density of the lowest unoccupied orbital and the formal charge at the position of amino group or at the position of nitrogen atom in sulphonamide. The diuretic activities of triazine derivatives show good correlation with the reaction indices, the first frontier superdelocalizability of the lowest unoccupied orbital at the 1-position (carbon atom) and the π-electron density of the unoccupied orbital at the 4-position (nitrogen atom). The positions of these diuretics, which are assumed to play the important role in diuretic action, are the positions in the group =N-C-N=. As the values of the Coulomb integral and the resonance integral of trifluoromethyl group (CF3) and the Coulomb integral of carbon atom adjacent to this pseudo-atom, α+2.0β, 1.0β and α — 0.1β are employed.

Mass Spectral Studies of Aza- and Diazabenzobicycloalkanes. II. Some Aspects of Mass Spectrometry of 1, 3-Bridged 1, 2, 3, 4-Tetrahydronaphthalenes, 2, 4-Bridged 1, 2, 3, 4-Tetrahydroisoquinolines and 1, 3-Bridged 1, 2, 3, 4-Tetrahydroquinolines

The mass spectra of 1, 3-bridged 1, 2, 3, 4-tetrahydronaphthalenes (I, I', II, III and IV), 2, 4-bridged 1, 2, 3, 4-tetrahydroisoquinolines (VI, VII and VII') and 1, 3-bridged 1, 2, 3, 4-tetrahydroquinolines (VIII and IX) were examined. Fragmentation pathways of these compounds are discussed. The compounds I-V undergo two major fragmentations ; fission of the B-ring to give fragment ions of C-ring and A-ring, and formation of naphthalene and small nitrogen-containing fragment ions. While, the compounds VI-IX decompose to form quinoline- or isoquinoline-type fragment ions by loss of C-ring moiety. The position of nitrogen atom plays a dominant role in determining the predominance of the fragmentation.

Synthetic studies on chalcone-flavanone groups. IV. Ultraviolet absorption spectra of 2',4'-dihydroxychalcone, 4'-(benzyloxy)-2'-hydroxychalcone, and their pyridine analogs

The ultraviolet absorption spectra of 2', 4'-dihydroxychalcone (V), 4'-(benzyloxy)-2'-hydroxychalcone (VI) and azachalcones (Ila-c, IIIa-c) corresponding to V and VI are reported. These chalcones and azachalcones show two absorption maxima in the wavelength region over 280 mμ, λ1 (345-350 mμ) and λ2 (282 -324 mμ) respectively. It was confirmed that λ1 is due to the electronic nature of the conjugation system of dihydroxybenzoyl group (IA) and λ2 is due to that of cinnamoyl group (IB). Relations between the values of λ1 and λ2, and the position of nitrogen atom in the azachalcones were also discussed.

The Norcaradiene Problem

AbstractCompounds having the norcaradiene structure are stable if one of the double bonds of the norcaradiene also belongs to a benzene ring or if C atoms 1 and 6 are fixed in position by a bridge. A similar effect that favors the norcaradiene form is produced by the incorporation of nitrogen atoms in positions 3 and 4. Cycloheptatriene and most of the simply substituted tropilidenes exist exclusively in the monocyclic triene form. It has been possible in some cases to detect a valence‐tautomeric equilibrium between the norcaradiene and the cycloheptatriene ring system. Non‐classical stabilization of compounds having norcaradiene or cycloheptatriene structure in the sence of a pseudoaromatic “homobenzene” is only very slight, if it occurs at all.

Absorption spectra of some imidazolid-4-one derivatives, the dimerocyanines. IV. Effect of temperature on dye absorption spectrum in the visible region

Observation at different temperatures of uv absorption spectra of a number of imidazolid-4-one derivatives, dimerocyanines, shows that change in temperature of the solution causes considerable alterations in the absorption curves. In agreement with previous results, this corresponds to a displacement of equilibrium between two dye conformations in solution. One conformation has theβ-dicarbonyl group more coplanar with respect to the plane of the molecule than the other. The transition energy required to convert one form into the other (ΔH) is found from a plot of the logarithms of the equilibrium constants against the reciprocal of the temperature. It is shown that ΔH depends on the substituent at the nitrogen atom in position 3 of the imidazolidone ring.

STUDIES ON THE STRUCTURES OF DIAZINE N-OXIDES. II. DIPOLE MOMENTS OF SOME ALKOXY-DERIVATIVES OF PYRIMIDINE, PYRIDAZINE AND THEIR N-OXIDES.

The dipole moments of some pyrimidine, pyridazine, and their N-oxides (I to VIII) were measured in benzene solution at 25°. In alkoxy derivatives, the moments of two forms, cis and trans were considered by the bending structure of alkoxyl group, and the respective vectorical sums were calculated. Alkoxydiazines whose respective alkoxyl group is attached to the neighboring position of nitrogen atom showed all to exist as cis form. By the steric hindrance of cis form, in the alkoxy-diazine mono N-oxide the oxygen atom was postulated to attach to the nitrogen atom distant from the alkoxyl group.

The carbon and nitrogen precursors of bacterial purines

The synthesis of purines in Aerobacter aerogenes was studied by culturing the organism in a dextrose-ammonium sulfate medium with added isotopically labeled compounds. Glycine is incorporated into the 4, 5, and 7 positions of adenine and guanine of bacterial nucleic acids. Carbon dioxide is incorporated into position 6 of these purine bases, and into positions 2 plus 8 through reduction to formate. Acetate does not play a role in bacterial purine synthesis. Nitrogen atoms in positions 1,3, and 9 arise from the nitrogen of ammonium sulfate either directly or through some donor system. The synthesis of adenine and guanine by the same mechanisms present in animal tissue is indicated.