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PubMed1975

Metabolism in the rat of some pyrazine derivatives having flavour importance in foods.

1. The metabolism of several alkyl- and alkoxy-substituted pyrazines in the rat has been investigated. 2. Alkyl substituted compounds were oxidized to the corresponding acids which were excreted in the urine as such or as their glycine cojugates. The extent of oxidation was reduced when two adjacent alkyl groups were present. In the latter case ring hydroxylation also occurred. Methoxy-substituted pyrazines underwent O-demethylation and ring hydroxylation. 3. Little or no biliary excretion of the pyrazines or their metabolites occurred. 4. Some preliminary results on the metabolism of 2-isobutyl-3-methoxy-pyrazine (the major characteristic flavour component of bell pepper) have been obtained. 5. For comparative purposes the metabolism of some similarly substituted pyridines was investigated.

Animals↗
PubMed2006

Conformational behavior of pyrazine-bridged and mixed-bridged cavitands: a general model for solvent effects on thermal "vase-kite" switching.

The controllable switching of suitably bridged resorcin[4]arene cavitands between a "vase" conformation, with a cavity capable of guest inclusion, and a "kite" conformation, featuring an extended flattened surface, provides the basis for ongoing developments of dynamic molecular receptors, sensors, and molecular machines. This paper describes the synthesis, X-ray crystallographic characterization, and NMR analysis of the "vase-kite" switching behavior of a fully pyrazine-bridged cavitand and five other mixed-bridged quinoxaline-bridged cavitands with one methylene, phosphonate, or phosphate bridge. The pyrazine-bridged resorcin[4]arene cavitand displayed an unexpectedly high preference for the kite conformation in nonpolar solvents, relative to the quinoxaline-bridged analogue. This observation led to extensive solvent-dependent switching studies that provide a detailed picture of how solvent affects the thermal vase-kite equilibration. As for any thermodynamic process in the liquid phase, the conformational equilibrium is affected by how the solvent stabilizes the two individual states. Suitably sized solvents (benzene and derivatives) solvate the cavity of the vase form and reduce the propensity for the vase-to-kite transition. Correspondingly, the kite geometry becomes preferred in bulky solvents such as mesitylene, incapable of penetrating the vase cavity. As proposed earlier by Cram, the kite form is preferred at low temperatures due to the more favorable enthalpy of solvation of the enlarged surface. Furthermore, the kite conformation is more preferred in solvents with substantial hydrogen-bonding acidity: weak hydrogen-bonding interactions between the mildly basic quinoxaline and pyrazine nitrogen atoms and solvent molecules are more efficient in the open kite than in the closed vase form. Vase-to-kite conversion is entirely absent in dipolar aprotic solvents lacking any H-bonding acidity. Thermal vase-kite switching requires fully quinoxaline- or pyrazine-bridged cavitands, whereas pH-controlled switching is also applicable to systems incorporating only two or three such bridges.

Journal Article↗
PubMed2005

Structure and properties of bivalent nickel and copper complexes with pyrazine-amide-thioether coordination: stabilization of trivalent nickel.

Acyclic pyrazine-2-carboxamide and thioether containing hexadentate ligand 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpzctb), in its deprotonated form, has afforded light brown [Ni(II)(bpzctb)](1)(S=1) and green [Cu(II)(bpzctb)](2)(S=1/2) complexes. The crystal structures of 1.CH(3)OH and 2.CH(2)Cl(2) revealed that in these complexes the ligand coordinates in a hexadentate mode, affording examples of distorted octahedral M(II)N(2)(pyrazine)N'(2)(amide)S(2)(thioether) coordination. Each complex exhibits in CH(2)Cl(2) a reversible to quasireversible cyclic voltammetric response, corresponding to the Ni(III)/Ni(II)(1) and Cu(II)/Cu(I)(2) redox process. The E(1/2) values reveal that the complexes of bpzctb(2-) are uniformly more anodic by approximately 0.2 V than those of the corresponding complexes with the analogous pyridine ligand, 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpctb), attesting that compared to pyridine, pyrazine is a better stabilizer of the Ni(ii) or Cu(i) state. Coulometric oxidation of the previously reported complex [Ni(II)(bpctb)] and 1 generates [Ni(III)(bpctb)](+) and [Ni(III)(bpzctb)](+) species, which exhibit a LMCT transition in the 470--480 nm region and axial EPR spectra corresponding to a tetragonally elongated octahedral geometry. Complex 2 exhibits EPR spectra characteristic of the d(z(2)) ground state.

Journal Article↗
PubMed1985

Pyrazines responsible for the potatolike odor produced by some serratia and cedecea strains.

The pyrazines responsible for the potatolike odor produced by some Serratia and Cedecea cultures were identified by gas-liquid chromatography (with flame ionization and thermoionic ionization detectors) and mass spectrometry. Alkylpyrazines were produced by the six strains studied irrespective of their odors. The major alkyl-methoxypyrazine produced by Cedecea davisae was 3-sec-butyl-2-methoxypyrazine, and that produced by odoriferous Serratia strains (S. rubidaea, S. odorifera, and S. ficaria) was 3-isopropyl-2-methoxy-5-methyl-pyrazine. Other pyrazines produced by some strains were 3-isopropyl-2-methoxypyrazine, 3-isobutyl-2-methoxypyrazine, 3-sec-butyl-2-methoxy-5-methylpyrazine, and 3-isobutyl-2-methoxy-6-methylpyrazine. Some of these pyrazines had not previously been found as natural products or to be produced by bacteria.

Journal Article↗
PubMedDate not supplied

Effect of conformation on the chemiluminescence efficiency of light-producing 2-methyl-6-(4-methoxyphenyl)imidazo[1,2-alpha]pyrazin-3(7H)-ones.

Analogues of the light-producing substrate 2-methyl-6-(4-methoxyphenyl)imidazo[1,2-alpha]pyrazin-3(7H)-one, with restrictions on the dihedral angles between the pyrazine and the 4-methoxyphenyl rings, were synthesized. These compounds were used to investigate the effects of the conformation between the pyrazine and 4-methoxyphenyl rings on their chemiluminescence efficiencies in aqueous solutions. The effects of the conformation on the chemiluminescence efficiencies were clearly observed; the decrease of the dihedral angle caused a light-enhancing effect and, conversely, the increase of the angle dramatically decreased the chemiluminescence efficiency. These effects on the chemiluminescence efficiencies are attributed to the influence of the conformation on the fluorescence efficiency of the emitter.

Amides↗
PubMed2005

The chafer pheromone buibuilactone and ant pyrazines are also produced by marine bacteria.

Headspace extracts obtained from agar plate cultures of two marine bacteria from the North Sea (Germany), Loktanella strain BIO-204 and Dinoroseobacter shibae strain DFL-27, were analyzed by GC-MS. Several gamma-lactones and one delta-lactone were identified, besides pyrazines and some sulfur compounds. The absolute configuration of the major lactone (R,Z)-dodec-5-en-4-olide, known as buibuilactone, a pheromone of several scarab beetles, was determined by a new catalytic enantioselective synthesis and GC on a chiral stationary phase. Unsaturated lactones in the extracts included (E)-dodec-5-en-4-olide and the regioisomer (Z)-dodec-6-en-4-olide, previously identified as a component of black-tailed deer urine. The pyrazines 2-butyl-3,6-dimethylpyrazine and 2-isopentyl-3,6-dimethylpyrazine were identified by comparison with synthesized material. The latter compound is a known ant pheromone, as is another identified pyrazine, 2-ethyl-3,6-dimethylpyrazine. The striking similarity between insect pheromones and these bacterial volatiles is discussed, suggesting the possibility of more widespread occurrence of symbiosis between microorganisms and insects than previously thought.

4-Butyrolactone↗
PubMed1994

Pharmacokinetics, metabolism and distribution of 1,2-dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo [1,2-A] pyrido [3,2-E] pyrazine-5-oxide in C3H mice.

PURPOSE: 1,2-Dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo [1,2-a] pyrido [3,2-e] pyrazine-5-oxide (RB90740) is a bioreductive drug with an oxic to hypoxic toxicity ratio of 16 in cultured V79 cells in vitro. The aim of this study was to examine the pharmacokinetics, metabolism and distribution of the drug in tumor bearing C3H mice. METHODS AND MATERIALS: A high pressure liquid chromatography assay for the quantitative determination of concentrations of the drug and its metabolites has been developed and used to examine their distribution in blood, RIF-1 and KHT tumors, brain, muscle, and liver tissue. Urine and feces collected for 24 h after drug administration have been examined for the drug and its metabolism products. RESULTS: Three metabolites, two of which have been identified, have been observed in mouse tissue. 1,2-Dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo [1,2-a]pyrido[3,2-e]pyrazine (RB92815) is the two-electron reduced species, which is observed in liver, urine and occassionally in tumor samples. 1,2-dihydro-8-(4-piperazinyl)-4-phenylimidazo [1,2-a]pyrido[3,2-e]pyrazine-5-oxide (RB1739), the N-demethylated compound, is observed in urine and liver. Elimination of the drug after an intraperitoneal dose of 50 mg/kg is biphasic with t(1)2 alpha = 3 min and t(1)2 beta = 219 min. The area under the curve for blood concentration vs. time is 1.4 mg ml min-1. The drug is preferentially taken up into tumor tissue as is apparent from the area under the curve values for RIF-1 (28.3 mg ml min-1) and KHT (18.4 mg ml min-1) tumors. CONCLUSION: From these values of the area under the curve it is suggested that the drug is present in tumor tissue at concentrations sufficient to eliminate the hypoxic fraction provided reduction to a toxic species occurs. Bioreduction by the addition of two electrons to form RB92815 occurs in some tumors, but it is not known if this is due to an obligate two-electron detoxifying step or if reduction occurs by single electron additions via a toxic free radical species.

Animals↗
PubMed2004

Cyclodextrin-bound 6-(4-methoxyphenyl)imidazo[1,2-alpha+/-]pyrazin-3(7H)-ones with fluorescein as green chemiluminescent probes for superoxide anions.

In providing chemiluminescent probes that have high chemiluminescence intensity and high specificity to superoxide anions, novel chemiluminescent probes involving cyclodextrins covalently bound to 6-(4-methoxyphenyl)imidazo[1,2-alpha]pyrazin-3(7H)-one with fluorescein were synthesized and characterized. Using the hypoxanthine-xanthine oxidase system for the generation of the superoxide anions, these novel chemiluminescent probes showed higher superoxide-induced chemiluminescence intensity than that of 6-[4-[2-[N(')-(5-fluoresceinyl)thioureido]-ethoxy]phenyl]-2-methylimidazo[1,2-alpha]pyrazin-3(7H)-one (FCLA). When tested at a probe concentration of 1.0 microM, compound 6, in which 6-(4-methoxyphenyl)imidazo[1,2-alpha]pyrazin-3(7H)-one and fluorescein are covalently attached on the secondary and primary hydroxyl faces of gamma-cyclodextrin, respectively, showed green luminescence intensity that was 26 times that of FCLA, which was also the highest luminescence intensity in this present study. At probe concentrations of less than 1.0 microM, the ratio of the superoxide-dependent chemiluminescence intensity to the background chemiluminescence intensity for compound 6 was higher than that of FCLA. This high superoxide-induced chemiluminescence intensity and superoxide specificity in low probe concentrations indicates that 6 can be more effective than FCLA toward the measurement of superoxide anions.

Cyclodextrins↗
PubMed2004

Synthesis and preliminary evaluation of some pyrazine containing thiazolines and thiazolidinones as antimicrobial agents.

A series of N'-[3,4-disubstituted-1,3-thiazol-2(3H)-ylidene]-2-(pyrazin-2-yloxy)acetohydrazide 11-66 and N'-[(2Z)-3-(4-bromophenyl)-4-oxo-1,3-thiazolidin-2-ylidene]-2-(pyrazin-2-yloxy)acetohydrazide 68-74 were synthesized using appropriate synthetic route. The entire test compounds 11-66 and 68-74 were assayed in vitro for antibacterial activity against two different strains of Gram-negative (E. coli and S. typhi), Gram-positive (S. aureus and B. subtilis) bacteria and the antimycobacterial activity was evaluated against H(37)Rv strain of Mycobacterium tuberculosis. The minimum inhibitory concentration (MIC) was determined for test compounds and for reference standards. The test compounds showed significant antibacterial and antimycobacterial activity against the microbial strains used, when tested in vitro. In general, pyrazine ring and substituted thiazoline ring are essential for antimicrobial activity. Among the compounds tested, compounds 11, 12 and 40 were found to be most potent. The toxicity of most potent compounds 11, 12 and 40 were determined using hemolytic assay and minimal hemolytic concentration (MHCs) were determined. The test compounds were found to be nontoxic up to a dose level of 250 microg/mL.

Anti-Bacterial Agents↗
PubMed1997

Antiproliferative effects of imidazo[1,2-a]pyrazine derivatives on the Dami cell line.

Since cyclic 3',5'-adenosine monophosphate (cAMP) is involved in cell proliferation and as previous data showed that imidazo[1,2-alpha]pyrazine derivatives (PAB12, PAB30, PAB40, SCA40, SCA41, and SCA44) inhibited cAMP breakdown by a phosphodiesterase (PDE)-inhibitory effect, the aim of the present study was to investigate the effects of these derivatives on proliferation of the Dami cell line in relation with their actions on cAMP content and on PDE isoenzymes isolated from Dami cells. SCA41 and SCA44 inhibited cell growth in a dose-dependent manner, while SCA40 and PAB40 induced a weak inhibition. Growth inhibitions were 40%, 91%, and 60% for SCA41, SCA44 (at 100 microM), and IBMX (at 100 microM), respectively, and could not be related to their effects on cAMP levels. In addition, although all compounds potentiated cAMP formation by prostaglandin E1 (PGE1), no potentiations were observed when the antiproliferative effects of SCA41 and SCA44 were considered. Investigation of derivatives on PDE isoenzymes III, IV, and V indicated non-selective PDE inhibitory effects for SCA41 and SCA44, while SCA40 elicited preferences for type III, and PAB30 and PAB40 preferences for type IV isoenzymes. These effects could not totally explain the antiproliferative activity of the derivatives. The activation of P2 purinoceptors by imidazo[1,2-a]pyrazine did not lead to their antiproliferative effects. Thus, the mechanism of the antiproliferative effects of the compounds remains to be determined. It does, however, depend on the chemical substitutions of the imidazo[1,2-a]pyrazine skeleton and in particular on the 2-carbonitrile presence and the length of the 8-aminoaliphatic group.

1-Methyl-3-isobutylxanthine↗
PubMed2005

Correlation of acrylamide generation in thermally processed model systems of asparagine and glucose with color formation, amounts of pyrazines formed, and antioxidative properties of extracts.

The relations between the formation of acrylamide and color, pyrazines, or antioxidants in an asparagine/d-glucose browning model system under various conditions were investigated. The highest level of acrylamide was produced in the asparagine/glucose (1:3) system heated at 170 degrees C for 30 min (2629 microg/g asparagine). Color intensity increased with temperature and heating time. The formation of pyrazines increased steadily with an increase of temperature (140-170 degrees C) and heating time (15-60 min). Antioxidant formation varied among the samples heated under different conditions. A clear correlation between formation of acrylamide and browning color was obtained. The formation of acrylamide was linearly correlated with the formation of total pyrazines during the initial stages of the Maillard reaction. No obvious correlation between formation of acrylamide and antioxidants was observed. However, excess amounts of asparagine increased the formation of antioxidants, whereas excess amounts of glucose reduced its formation.

Acrylamides↗
PubMed1995

8-Amino-3-benzyl-1,2,4-triazolo[4,3-a]pyrazines. Synthesis and anticonvulsant activity.

Eleven substituted 8-amino-3-benzyl-1,2,4-triazolo[4,3-a] pyrazines were synthesized and tested for anticonvulsant activity against maximal electroshock-induced seizures (MES) in rats. The compounds were prepared in four stages from the phenylacetonitriles. I. The intermediate (2,2,2-triethoxyethyl)benzenes III were condensed with 2-chloro-3-hydrazinopyrazine (IV) to provide the 3-benzyl-8-chloro-1,2,4-triazolo[4,3-a]pyrazines V. The latter were converted to the 8-amine targets VI with methylamine or ammonia. Several compounds exhibited potent activity against MES; the 3-(2-fluorobenzyl)-8-(methylamino) and 3-(2,6-difluorobenzyl)-8-(methylamino)congeners (4 and 12) exhibited the best anticonvulsant activity with oral ED50S of 3 mg/kg. The 1,2,4-triazolo[4,3-a]pyrazine ring system serves as a bioisostere of the purine ring for anticonvulsant activity; however, these agents exhibit less propensity to cause emesis.

Animals↗
PubMed1992

Synthesis and muscarinic activity of quinuclidinyl- and (1-azanorbornyl)pyrazine derivatives.

The synthesis and cortical muscarinic activity of a novel series of pyrazine-based agonists is described. Quinuclidine and azanorbornane derivatives were prepared either by reaction of lithiated pyrazines with azabicyclic ketones, followed by chlorination and reduction, or by reaction of the lithium enolate of the azabicyclic ester with 2-chloropyrazines followed by ester hydrolysis and decarboxylation. Substitution at all three positions of the heteroaromatic ring has been explored. Optimal muscarinic agonist activity was observed for unsubstituted pyrazines in the azanorbornane series. The exo-1-azanorbornane 18a is one of the most efficacious and potent centrally active muscarinic agonists known. Studies on the 3-substituted derivatives have provided evidence of the preferred conformation of these ligands for optimal muscarinic activity. Substitution at C6 gave ligands with increased affinity and reduced efficacy. Moving the position of the diazine ring nitrogens to give pyrimidine and pyridazine derivatives resulted in a significant loss of muscarinic activity.

Animals↗
PubMed1990

Potential antimitotic agents. Synthesis of some ethyl benzopyrazin-7-ylcarbamates, ethyl pyrido[3,4-b]pyrazin-7-ylcarbamates, and ethyl pyrido[3,4-e]-as-triazin-7-ylcarbamates.

Ring analogues and derivatives of the 1,2-dihydropyrido[3,4-b]pyrazin-7-ylcarbamates (e.g., 29), antimitotic agents with antitumor activity, were prepared in the search for compounds with greater selectivity. Methods were developed for the conversion of substituted benzoic acids (1-4) to give benzopyrazines (12-16 and 21) and of substituted pyridin-2-carbamates (23, 38, and 41) to give 2-aminopyrido[3,4-b]pyrazin-7-ylcarbamates (32 and 36) and pyrido[3,4-e]-as-triazin-7-ylcarbamates (47 and 50). In vitro evaluation indicated that activity was reduced by removal of the pyridine ring nitrogen of 29 to give 14 and was destroyed by increasing the basicity of the pyrazine ring of 29 to give 32 and 47.

Animals↗
PubMed1988

Imidazo[1,2-a]pyrimidines and imidazo[1,2-a]pyrazines: the role of nitrogen position in inotropic activity.

Congestive heart failure is a major medical problem for which existing medicaments have provided limited benefit. Recent new experimental drugs, including imidazo[4,5-b]- and imidazo[4,5-c]pyridines, have both inotropic and vasodilatory properties. Subtle changes in nitrogen position of these compounds have been shown to dramatically affect potency. We have synthesized a series of imidazo[4,5-b]- and -[4,5-c]pyridine analogues having an imidazo nitrogen relocated at the bridgehead position. The superior inotropic activity of the [4,5-c]pyridines as compared to [4,5-b]pyridines is reaffirmed by the activity of our analogues. The biological equivalence of imidazo[4,5-b]pyridines with imidazo[1,2-a]pyrimidines and imidazo[4,5-c]pyridines with imidazo[1,2-a]pyrazines is demonstrated. Further, 2-[2-methoxy-4-(methylsulfenyl)phenyl]imidazo[1,2-a]pyrazine and 2-[2-methoxy-4-(methylsulfonyl)phenyl]-imidazo[1,2-a]pyrazine are potent inotropic agents both in vitro and in vivo.

Animals↗
PubMed2005

Synthesis and structure-activity relationships of pyrazine-pyridine biheteroaryls as novel, potent, and selective vascular endothelial growth factor receptor-2 inhibitors.

There is much evidence that direct inhibition of the kinase activity of vascular endothelial growth factor receptor-2 (VEGFR-2) will result in the reduction of angiogenesis and the suppression of tumor growth. Palladium-catalyzed C-C bond, C-N bond formation reactions were used to assemble various pyrazine-pyridine biheteroaryls as potent VEGFR-2 inhibitors. Among them, 4-{5-[6-(3-chloro-phenylamino)-pyrazin-2-yl]-pyridin-3-ylamino}-butan-1-ol (39) and N-{5-[6-(3-chloro-phenylamino)-pyrazin-2-yl]-pyridin-3-yl}-N',N'-dimethyl-ethane-1,2-diamine (41) exhibited the highest kinase selectivity against fibroblast growth factor receptor kinase, platelet-derived growth factor receptor kinase, and glycogen synthase kinase-3. All of these compounds showed good cellular potency to inhibit VEGF-stimulated proliferation of human umbilical vein endothelial cells (HUVEC) but with modest effects on the unstimulated growth of HUVEC. The low inhibition of these compounds to the growth of tumor cell lines, such as HeLa, HCT-116, and A375 further confirms that these VEGFR-2 inhibitors are not cytotoxic agents. The in vivo antitumor activity of 39 and 41 were demonstrated in the A375 human melanoma xenograft nude mice model. Molecular modeling (QSAR analysis) was conducted in an attempt to rationalize the observed structure-activity relationship.

Aminopyridines↗
PubMed1998

Novel, highly potent aldose reductase inhibitors: (R)-(-)-2-(4-bromo-2-fluorobenzyl)-1,2,3,4- tetrahydropyrrolo[1,2-a]pyrazine -4-spiro-3'-pyrrolidine-1,2',3,5'-tetrone (AS-3201) and its congeners.

A series of novel tetrahydropyrrolo[1,2-a]pyrazine derivatives were synthesized and evaluated as aldose reductase inhibitors (ARIs) on the basis of their abilities to inhibit porcine lens aldose reductase (AR) in vitro and to inhibit sorbitol accumulation in the sciatic nerve of streptozotocin-induced diabetic rats in vivo. Of these compounds, spirosuccinimide-fused tetrahydropyrrolo[1, 2-a]pyrazine-1,3-dione derivatives showed significantly potent AR inhibitory activity. In the in vivo activity of these derivatives, 2-(4-bromo-2-fluorobenzyl)-1,2,3,4-tetrahydropyrrolo[1, 2-a]pyrazine-4-spiro-3'-pyrrolidine-1,2',3,5'-tetrone (23t) (SX-3030) showed the best oral activity. The enantiomers of 23t were synthesized, and the biological activities were evaluated. It was found that AR inhibitory activity resides in the (-)-enantiomer 43 (AS-3201), which was 10 times more potent in inhibition of the AR (IC50 = 1.5 x 10(-8) M) and 500 times more potent in the in vivo activity (ED50 = 0.18 mg/kg/day for 5 days) than the corresponding (+)-enantiomer 44 (SX-3202). From these results, AS-3201 was selected as the candidate for clinical development. The absolute configuration of AS-3201 was also established to be (R)-form by single-crystal X-ray analysis. In this article we report the preparation and structure-activity relationship (SAR) of tetrahydropyrrolopyrazine derivatives including a novel ARI, AS-3201.

Aldehyde Reductase↗
PubMed2006

Straightforward access to pyrazines, piperazinones, and quinoxalines by reactions of 1,2-diaza-1,3-butadienes with 1,2-diamines under solution, solvent-free, or solid-phase conditions.

The preparation of tetrahydropyrazines, dihydropyrazines, pyrazines, piperazinones, and quinoxalines by 1,4-addition of 1,2-diamines to 1,2-diaza-1,3-butadienes bearing carboxylate, carboxamide, or phosphorylated groups at the terminal carbon and subsequent internal heterocyclization is described. The solvent-free reaction of carboxylated 1,2-diaza-1,3-butadienes with the same reagents affords piperazinones, while phosphorylated 1,2-diaza-1,3-butadienes yield phosphorylated pyrazines. The solid-phase reaction of polymer-bound 1,2-diaza-1,3-butadienes with 1,2-diamines produces pyrazines.

Amines↗