Pyrrole Type Research Articles

Transition metal complexes of bis(imidazol-2-yl) derivatives of dipeptides

Copper(II), nickel(II) and zinc(II) complexes of the dipeptides containing chelating bis(imidazolyl) agents at the C-termini (GlyLeu-BIMA, LeuGly-BIMA, PheGly-BIMA and AlaPro-BIMA; BIMA = bis(imidazol-2-yl)methylamine) were studied by potentiometric, UV-VIS, EPR and MALDI-MS techniques. The imidazole nitrogen donor atoms were described as the primary metal binding sites forming stable mono- and bis-(ligand) complexes in the acidic pH range. The formation of dinuclear complexes was detected in equimolar solutions of copper(II) and dipeptides and various isomeric forms of these species ([Cu2L2]4+ and [Cu2H−2L2]2+) were indentified by EPR measurements. Deprotonation and co-ordination of the amide groups of dipeptides took place in slightly alkaline solution resulting in the formation of [MH−2L] complexes of copper(II) and nickel(II). Metal ion co-ordination of one of the imidazole nitrogen donor atoms promoted the ionization of the pyrrole type N(1)H group of imidazole in copper(II) complexes and resulted in the formation of a trinuclear complex ([Cu3H−6L2]). The latter species contains negatively charged bridging imidazolato residues.

Photochemical modification of some polynaphthalimides

A series of polynaphthalimdes from dinaphthalene dianhydride and aromatic diamines mainly with alkyl substituents at ortho position to amine groups along with the model compounds has been synthesized using one-step high temperature polycondensation. It was found that in the case of the model compounds and the polymers synthesized from diamines with alkyl groups having at a carbon two hydrogen atoms, cyclodehydration process can take place during heating or UV irradiation and formation of additional cycle of pyrrole structure was observed. The polynaphthalimides synthesized from aromatic diamines substituted with alkyl groups can be modified under heating or UV irradiation, towards additional ring formation of pyrrole type, which causes an increase of the polymers glass transition temperatures.

Ab initio calculation of the NMR shielding constants for histamine

The gage-independent atomic orbital (GIAO) approach is used within the coupled Hartree-Fock approximation to compute the 1H, 13C and 15N NMR shielding constants in two tautomeric forms of both the histamine molecule and its protonated form. An analysis of the results shows that the protonation on the end of the chain changes its nitrogen shielding constants of the pyridine and pyrrole type. These changes are much higher for the N(3)-H than for the N(1)-H tautomer.

State analysis of nitrogen in carbon film derived from polyimide Kapton

The carbon films prepared from polyimide Kapton were investigated by XPS and elemental analysis. The chemical states of carbon and nitrogen gradually changed with carbonization temperature and the changes in the peak intensity ratio of I[ N1s] I[ C1s] by XPS were consistent with N C mole ratios by elemental analysis. The N1s peak around 401 eV which was a main component at 1200 °C was considered to correspond to quaternary species such as a pyrrole type nitrogen. This species may exist in the carbon films prepared at 2000 °C and affect their properties.

Synthesis of N-Phenylsulfonyl Protected Furo[3,2-b]pyrroles

Protection of nitrogen atom of heterocyclic molecules, such as indole and pyrrole types, enables various reactions of these systems. N-Phenylsulfonyl derivatives, which have been widely used for this purpose, were prepared in the indole series by the reaction of N-sodium and N-lithium salts with benzenesulfonyl chloride. This method requires waterfree and oxygenfree conditions. On the other hand, the phase transfer catalysis conditions used in this work obviates these disadvantages. We therefore selected the latter method for the preparation of variously substituted 4-phenylsulfonylfuro[3,2-b]pyrroles (I - VII) and 1-phenylsulfonylbenzo[b]furo[3,2-b]pyrroles (VIII - IX).

Molecular mechanics (MM3). Calculations on nitrogen-containing aromatic heterocycles

The MM3 force field has been extended to cover aromatic heterocycles of the pyridine and pyrrole types. Structures (32 compounds), heats of formation (35 compounds), dipole moments (35 compounds), and vibrational spectra (11 compounds) have been examined, and the results are good for structure and fair for the other its

Relation between functional forms of coal nitrogen and formation of nitrogen oxide (NOx) precursors during rapid pyrolysis

The formation of NO x precursors during rapid pyrolysis was investigated for 20 coals covering wide ranks at temperatures of 853-1488 K to elucidate the influence of coal properties on NO x formation during coal combustion. It was found that the main compositions of volatile nitrogen are HCN, NH 3 , and N 2 under these experimental conditions. Their yields are strongly dependent on coal types and pyrolysis temperature. By analyzing functional forms of coal nitrogen in parent coals and chars after pyrolysis using X-ray photoelectron spectroscopy, the relation between nitrogen functionality and formation of nitrogen-containing species has been further demonstrated. Three nitrogen functional forms of pyrrole type, pyridine type, and quaternary nitrogen are observed for all coals

Substrate-specificity of glutamine transporters in membrane vesicles from rat liver and skeletal muscle investigated using amino acid analogues

We investigated the effects of glutamine and histidine analogues on glutamine transport processes in membrane vesicles prepared from rat liver (sinusoidal membrane) and skeletal muscle (sarcolemma). L-[14C]Glutamine is transported in these membranes predominantly by Systems N/Nm (liver and muscle respectively), and to a lesser extent by Systems A and L (e.g. about 60, 20 and 20% of total flux respectively via Systems N, A and L at 0.05 mM-glutamine in liver membrane vesicles). The glutamine anti-metabolites 6-diazo-5-oxo-L-norleucine and acivicin were relatively poor inhibitors of glutamine uptake into liver membrane vesicles (less than 25% inhibition at 20-fold excess) and appeared primarily to inhibit System A activity (i.e. N-methylaminoisobutyric acid-inhibitable glutamine uptake). In similar experiments azaserine (also a glutamine anti-metabolite) inhibited approx. 50% of glutamine uptake, apparently by inhibition of System A and also of System L (i.e. 2-amino-2-carboxybicyclo[2,2,1]heptane-inhibitable glutamine uptake). Glutamate gamma-hydroxamate, aspartate beta-hydroxamate, histidine and N'-methylhistidine were all strong inhibitors of glutamine uptake into liver membrane vesicles (greater than 65% inhibition at 20-fold excess), but neither homoglutamine nor N'-methylhistidine produced inhibition. L-Glutamate-gamma-hydroxamate was shown to be a competitive inhibitor of glutamine transport via System N (Ki approximately 0.6 mM). Glutamine uptake in sarcolemmal vesicles showed a similar general pattern of inhibition as in liver membrane vesicles. The results highlight limits on the substrate tolerance of System N; we suggest that the presence of both an L-alpha-amino acid group and a nitrogen group with a delocalized lone-pair of electrons (amide or pyrrole type), separated by a specific intramolecular distance (C2-C4 chain equivalent), is important for substrate recognition by this transporter.

Conversion of fuel nitrogen in coal volatiles to NO x precursors under rapid heating conditions

The formation of NO x precursors during the rapid pyrolysis of three Australian coals has been studied by the determination of HCN using long path length Fourier transform infrared spectrometry and of nitrogen-containing species in the tars using gas chromatography with a nitrogen-specific detector. Significant differences in the release rates of HCN were observed, and these can be reconciled with differences in the composition of the nitrogen fraction of the tars. The stability of the species containing nitrogen in five-membered (pyrrole type) rings is significantly lower than that of species with nitrogen in six-membered (pyridine type) rings. This results in the more rapid formation of HCN from those coals with a greater proportion of nitrogen in pyrrole type structures. At high pyrolysis temperatures (1000 °C), these results suggest that nitrogen released from the decomposition of nitrogen-containing aromatics can be reincorporated into high molecular weight products.

Fractionation of coal tar pitch with iodine

Coal tar pitch was fractionated by charge-transfer fractionation (CTF) with iodine as an electron acceptor. Chemical analyses of each fraction were made by means of flame thermionic detector gas chromatography (FTD-GC), FID-GC, and GC/MS. Results of CTF would indicate that basic nitrogen compounds (pyridine type) were concentrated in the component and interact strongly with iodine. On the other hand, neutral nitrogen compounds (pyrrole type) were not concentrated by CTF. The fractionation behavior of the aromatic hydrocarbons has been discussed

Nitrogen-tellurium-containing heterocycles. 3. Reaction of 2-phenylbenzotellurazole at the heteroatoms

Reactions of 2-phenylbenzotellurazole at both heteroatoms are studied. σ-Telluranes and molecular complexes with mercury and palladium salts are prepared. Exchange of a tellurium atom by sulfur is achieved. Alkylation of a heteroatom of the pyrrole type, the tellurium atom, is achieved in a series of benzazoles for the first time.

13C and 15N NMR investigation of the prototropic equilibrium of 2‐hydroxy‐3‐methylindazole

AbstractIt is shown that both 13C and 15N NMR measurements provide similar estimates of the position of the prototropic equilibrium exhibited by 2‐hydroxy‐3‐methylindazole in three solvents. The 15N NMR study of the pyridine and pyrrole types of nitrogen atoms provided the most quantitatively reliable results. The position of the prototropic equilibrium was found to be critically dependent on the acidity of the chosen solvent, the quinonoid form being predominant in weakly acidic media.

Beitr�ge zur Chemie der Pyrrolpigmente, LVIII Phytochrommodellstudien: Konformationsanalytische Untersuchungen an 2,3-Dihydrobilatrien-abc-Derivaten

Two 3,4-dihydropyrromethenones and two 2,3-dihydrobilatrienes-abc O-methylated at rings A and D resp. have been prepared. Their configurations were established as (Z), (E), (Z, Z, Z) and (Z, Z, Z), respectively, using1H-NMR-techniques (NOE); they are also shown to exist predominantly in the lactam form. Within the pyrromethene fragment of the bilatrienes the pyrrolic and pyrroleninic ring type depends on the position of O-methylation. A helical all-synperiplanar conformation in solution could be established for all cases by applying the lanthanide induced shift (LIS) technique.

Analytical and biological analyses of test materials from the synthetic fuel technologies: IV. Studies of chemical structure-mutagenic activity relationships of aromatic nitrogen compounds relevant to synfuels

Nitrogen-containing organic compounds from environmental sources are receiving increasing attention because of uniquely active mutagens which have been found in this class (Chrisp et al., 1978; Nagao and Sugimura, 1978; Guerin et al., 1980). Differences in mutagenic activities among the various organo-nitrogen compounds, i.e., pyrrole types, pyridine types and aniline types, have been noted consistently. Furthermore, differences among homologs of a particular compound type are often striking. Information in this paper engages the question of chemical structure/biological activity relationships. Activity data for several N-heterocyclic, nitro-, amino- (primary, secondary and tertiary), and amino- N-heterocyclic aromatic compounds are presented. The number of fused rings and the substituent type affect the mutagenic activities greatly. The trends observed are discussed generally with reference to molecular structural features.

Cyanation using the combined reagent, triphenyiphosphine–thiocyanogen (TPPT): a new general route to indole and pyrrole carbonitriles

Various types of indoles, pyrroles, and enamines react with the combined reagent, Ph3P–(SCN)2(TPPT) under mild conditions to give the corresponding cyanated compounds in high yields. The reaction mechanism of the cyanation is discussed.

Heterocyclic analogs of pleiadiene

The problem of the participation of a N-atom of the pyrrole type in six-membered heteroaromatic systems has been considered within the framework of Huckel's molecular orbital method. The π-electronic characteristics of heterocyclic analogs of pleiadiene and a number of heteroaromatic compounds related to them have been considered from the point of view of reactivity, structure, and physical properties.

Carbonic anhydrase: Studies of uncharged metal directed inhibitors

The zinc binding chelate system of carbonic anhydrase contauns two groups of labile protons; those on the zinc bound water molecule and those on the pyrrole type nitrogen of the imidazole ligands. As there is strong evidence to support the isolation of the activity generating dissociation to the chelate system an inhibitor study has been carried out to determine which of the two groups is responsible. The open coordination position on the essential zinc ion of bovine carbonic anhydrase B has been probed through the use of uncharged inhibitor molecules. Methanol inhibits by binding in a one to one stoichiometry to the enzyme. The equilibrium dissociation constant K i inflects from a value near 3 M at pH 5.3 to a value of 0.9 M at pH 7.6. The equivalence point located at pH 6.4 has the characteristics of the pK enz shifting to higher pHin the presence of small concentrations of monovalent anions. As well it would appear that the site of the methanol inhibition is identical to or at least sterically overlapping with the site occupied by the inhibitory monovalent anions Aniline like methanol interacts with the metal ion at a single binding site. The inhibition as given by the K i is constant below pH 7 at 22 mM. At higher pH values the binding affinity falls off governed by the deprotonation of a single group with a pK a near 7.2.

The mass spectra of 2‐alkyl N‐methyl pyrrolidines

AbstractThe mass spectra of a series of 2‐alkyl N‐methyl pyrrolidines have been examined and fragments which may be pyrrole type structures are apparent. These ions are most prominent in the spectra of the long chain alkyl derivatives.

THE UTILIZATION OF GLYCINE FOR THE BIOSYNTHESIS OF BOTH TYPES OF PYRROLES IN PROTOPORPHYRIN

Although it has been shown that glycine is the nitrogenous precursor of the protoporphyrin moiety of hemoglobin (1,2), it has not been previously established that glycine is utilized for the formation of all four pyrrole structures of the porphyrin. In protoporphyrin (Fig. 1) two of the pyrrole rings (I and II) contain methyl and vinyl side chains and two (III and IV) contain methyl and propionic acid side chains; it is conceivable that these two different pyrrole structures are synthesized in the animal organism from different precursors. Degradation experiments were therefore undertaken to study the distribution of isotopic nitrogen in N15-labeled heme, produced in vivo after the administration of N15-labeled glycine, in order to determine whether glycine is used in the synthesis of both pyrrole types. The degradation studies were carried out in a manner to give unequivocal data with respect to separation of the two different pyrrole structures found in protoporphyrin. Labeled hemin, obtained from the blood of a human and from the blood of ducks, after the administration of N16-labeled glycine, was converted into hematoporphyrin dimethyl ether which was subsequently oxidized to yield methylmethoxyethylmaleimide (from pyrrole rings I and II) and methyl propionic acid maleimide or hematinic acid (from pyrrole rings III and IV) (Fig. 1). It can be seen from Table I that in each experiment the N15 values of the methylmethoxyethylmaleimide from pyrrole rings I and II and of the hematinic acid from pyrrole rings III and IV were equal, and were identical with the Nls concentrations in the porphyrin. Therefore, these experiments demonstrate that glycine is utilized equally for the formation of the two types of pyrroles in the protoporphyrin. These findings are in harmony with the hypothesis that in the biosynthesis of protoporphyrin a pyrrole ring is formed which is a common precursor of both types of pyrrole structures found in the protoporphyrin. These studies do not as yet reveal the mechanism by which glycine is utilized in the biosynthesis of the porphyrin. However, this report, together with our previous work, demonstrated directly that the nitrogen of