Some properties of vicinal diol-epoxides derived from benzo(a)anthracene and benzo(a)pyrene

The alkylating properties of pairs of syn- and anti-isomers of 2 diol-epoxides derived from benzo(a)pyrene (BP) and of 1 derived from benz(a)anthracene (BA) have been investigated. Of the anti-diol-epoxides, anti-BP 7,8-diol-9,10-oxide was the most reactive compound towards DNA, towards sodium p-nitrothiophenolate in a non-aqueous solvent system, and towards 4-(p-nitrobenzyl)pyridine in aqueous solution; anti-BP 9,10,-diol-7,8-oxide was of intermediate reactivity and anti-BA 8,9-diol-10,11-oxide was least reactive. The syn-diol-epoxides gave unsatisfactory results with DNA and 4-(p-nitrobenzyl)pyridine because of their rapid solvolysis in aqueous solution, but with sodium p-nitrothiophenolate showed the order of reactivity syn-BP 7,8-diol-9,10-oxide greater than syn-BA 8,9-diol-10,11-oxide greater than syn-BP 9,10-diol-7,8-oxide. The products of the reaction between diol-epoxides and nucleic acids were examined by Sephadex LH-20 chromatography followed by high-pressure liquid chromatography (HPLC) and the diol-epoxides were shown to react principally with the guanosine and adenosine moieties of RNA.     

Oxidation of C4-hydroxyphenyl 1,4-dihydropyridines in dimethylsulfoxide and its reactivity towards alkylperoxyl radicals in aqueous medium

This work reports the electrochemical oxidation of three newly synthesized C4-hydroxyphenyl-substituted 1,4-dihydropyridine derivatives in dimethylsulfoxide. The reactivity of the compounds with ABAP-derived alkylperoxyl radicals in aqueous buffer pH 7.4, was also studied. The oxidation mechanism involves the formation of the unstable dihydropyridyl radical, which was confirmed by controlled-potential electrolysis (CPE) and ESR experiments. The final product of the CPE, that is, pyridine derivative, was identified by GC-MS technique for the three derivatives. A direct reactivity of the synthesized compounds toward ABAP-derived alkylperoxyl radicals was found. The pyridine derivative was identified by GC-MS as the final product of the reaction. Results reveal that this type of 1,4-DHPs significantly reacts with the radicals, even compared with commercial 1,4-DHP drugs with a well-known antioxidant ability.     

Biodegradation of pyridine in a completely mixed activated sludge process

A potential bacterial culture (P1), isolated from garden soil and identified as Pseudomonas pseudoalcaligenes-KPN, was used as a starter seed to develop the biomass in a completely mixed activated sludge (CMAS) reactor and the system was evaluated for treatment of wastewater containing pyridine. The results of this study indicate that pyridine could be degraded efficiently at a loading of 0.251 kg pyridine kg MLSS(-1) d(-1) (0.156 kg TOC kg MLSS(-1) d(-1)) and at an optimal hydraulic retention time (HRT) of 24 h. Pyridine was used as the sole source of carbon and nitrogen by the biomass. Ammonia-nitrogen (NH3-N) was formed due to the metabolism of the pyridine ring. In the present investigation, the performance of CMAS with reference to pyridine biodegradation and the bio-kinetic constants for the biodegradation of pyridine, in a continuous system, were computed. The results indicate that a CMAS system inoculated with P. pseudoalcaligenes-KPN, under optimum conditions of HRT and pyridine loading, gives a yield coefficient of (Y) 0.29, decay coefficient (Kd) 0.0011 d(-1), maximum growth rate constant (mumax) 0.108 d(-1) and saturation rate constant (Ks) 5.37 mg L(-1) for pyridine.     

Structural effects on the reactivity 1,4-dihydropyridines with alkylperoxyl radicals and ABTS radical cation

A series of eight commercial C-4 substituted 1,4-dihydropyridines and other synthesized related compounds were tested for direct potential scavenger effect towards alkylperoxyl radicals and ABTS radical cation in aqueous Britton-Robinson buffer pH7.4. A direct quenching radical species was established. The tested 1,4-dihydropyridines were 8.3-fold more reactive towards alkylperoxyl radicals than ABTS cation radical, expressed by their corresponding kinetic rate constants. Furthermore, NPD a photolyte of nifedipine and the C-4 unsubstituted 1,4-DHP were the most reactive derivatives towards alkylperoxyl radicals. The pyridine derivative was confirmed by GC/MS technique as the final product of reaction. In consequence, the reduction of alkylperoxyl and ABTS radicals by 1,4-dihydropyridines involved an electron transfer process. Also, the participation of the hydrogen of the 1-position appears as relevant on the reactivity. Results of reactivity were compared with Trolox.     

Mutagenicity of para-substituted alpha-methylstyrene oxide derivatives with Salmonella

A series of 5 para-substituted alpha-methylstyrene oxide derivatives have been synthesized and together with alpha-methylstyrene oxide as well as styrene oxide have been studied as to their mutagenicity with the TA100 and TA1535 strains of Salmonella typhimurium. A multiple regression analysis model has been developed which describes the mutagenicity of the alpha-methylstyrene oxides in TA100. An increase in van der Waals volume was the most important variable in the model with greater improvement occurring with inclusion of the Hammett values for the para substituents on the compounds. The alpha-methylstyrene oxides were less active alkylating agents with 4-(p-nitrobenzyl)pyridine than styrene oxide and with pyridine all reactivity was at the beta-epoxide carbon. However all the alpha-methylstyrene oxide derivatives, except for the bromo compound where toxicity was evident, showed mutagenicity values either greater or comparable to that of styrene oxide. These studies would indicate that reactivity at the beta-carbon should also be a factor in describing the mutagenicity of the parent styrene oxide series.     

Comparative induction of CYP1A1 expression by pyridine and its metabolites

We compared pyridine and five of its metabolites in terms of (i) in vivo induction of CYP1A1 expression in the lung, kidney, and liver in the rat and (ii) in vitro binding to, and activation of, the aryl hydrocarbon receptor (AhR) in cytosol from rat liver or Hepa1c1c7 cells. Following a single 2.5 mmol/kg ip dose of either pyridine, 2-hydroxpyridine, 3-hydroxypyridine, 4-hydroxypyridine, N-methylpyridinium, or pyridine N-oxide, CYP1A1 activity (ethoxyresorufin O-deethylase), protein level (as determined by Western blotting), and mRNA level (as determined by Northern blotting) were induced by pyridine, N-methylpyridinium, and pyridine N-oxide in the lung, kidney, and liver. The induction by N-methylpyridinium or pyridine N-oxide was comparable to or greater than that by pyridine in some tissues. 2-Hydroxypyridine and 3-hydroxypyridine caused tissue-specific induction or repression of CYP1A1, whereas 4-hydroxypyridine had no effect on the expression of the enzyme. Pyridine and its metabolites elicited weak activation of the aryl hydrocarbon receptor in a gel retardation assay in cytosol from rat liver but not Hepa 1c1c7 cells. However, the receptor activation did not parallel the in vivo CYP1A1 induction by the pyridine compounds, none of which inhibited binding of ?(3)H2,3,7, 8-tetrachlorodibenzo-p-dioxin to AhR in a competitive assay in rat liver cytosol. The findings are consistent with a role of pyridine metabolites in CYP1A1 induction by pyridine but do not clearly identify the role of aryl hydrocarbon receptor in the induction mechanism.     

An Efficient Approach for the Synthesis and Antitumor Evaluation of Novel Azo- and Anil-Linked with 3-Aminopyrazolo[3,4-b]pyridine

In this project, an effective procedure for constructing a new combination of pyrazolo[3,4-b]pyridine was depicted through the coupling of diazonium salt 2 of heterocyclic amine 1 with active methylene, enamine, and amidine moieties such as 3 , 5 , 7 , and 9 at 0–5 °C in pyridine to afford hydrazinylhydrazonoyl derivatives 4 , and diazenylheterocyclic derivatives 6 , 8 , and 10 , respectively. Also, aminopyrazolo[3,4-b]pyridine 1 condensed with different aryl or heteroaryl aldehydes in EtOH/AcOH gave the corresponding aldimine 14 , 15 , 16 . Compound 15 was cyclized via refluxing in DMF for 6 h to afford 18 , while the transformation of compound 16 with an alkyl halide afforded 19a , b . The synthesized compounds, explicated by spectral data and elemental analysis, were examined for their antitumor activities. The in vitro cytotoxic activity of new pyrazolo[3,4-b]pyridines against the A2780CP, MCF-7, and HepG-2 cell lines was evaluated using the reference doxorubicin. Compounds 15 and 19a exhibited high reactivity against the A2780CP cell lines, with IC₅₀ values of 35 and 17.9 μM, respectively. Also, compound 28 had the cytotoxic potential for A2780CP and MCF-7 cell lines, with IC₅₀ values of 14.5, and 27.8 μM, respectively.     

Probing Aspergillus niger glucose oxidase with pentacyanoferrate(III) aza- and thia-complexes

Complexes of pentacyanoferrate(III) and biologically relevant ligands, such as pyridine, pyrazole, imidazole, histidine, and other aza- and thia-heterocycles, were synthesized. Their spectral, electrochemical properties, electron exchange constants, electronic structure parameters, and reactivity with glucose oxidase from Aspergillus niger were determined. The formation of the complexes following ammonia replacement by the ligands was associated with the appearance of a new band of absorbance in the visible spectrum. The constants of the complexes formation calculated at a ligand-pentacyanoferrate(III) concentrations ratio of 10:1, were 7.5 x 10(-5), 7.7 x 10(-5), and 1.8 x 10(-3) s(-1) for benzotriazole, benzimidazole, and aminothiazole ligands, respectively. The complexes showed quasi-reversible redox conversion at a glassy carbon electrode. The redox potential of the complexes spanned the potential range from 70 to 240 mV vs. saturated calomel electrode (SCE) at pH7.2. For most of the complexes self-exchange constants (k(11)) were similar to or larger than that of hexacyanoferrate(III) (ferricyanide). The complexes containing pyridine derivatives and thia-heterocyclic ligands held a lower value of k(11) than that of ferricyanide. All complexes reacted with reduced glucose oxidase at pH7.2. The reactivity of the complex containing pyrazole was the largest in comparison to the rest of the complexes. Correlations between the complexes' reactivity and both the free energy of reaction and k(11) shows that the reactivity of pentacyanoferrates obeys the principles of Marcus's electron transfer theory. The obtained data suggest that large negative charges of the complexes decrease their reactivity.     

Biotreatment of waste gas containing pyridine in a biofilter

Industrial waste gas emissions containing pyridine are generated from pyridine manufacturing industries, and in industrial operations where pyridine is used as a solvent, as an intermediate for synthesis and as a catalyst for a variety of applications. Pyridine has unpleasant fishy odor with an odor index of 2390 and waste gaseous emissions containing pyridine require proper treatment prior to discharge. A biofilter, packed with compost and wood chips and inoculated with Pseudomonas pseudoalcaligenes-KPN for enrichment of pyridine-degrading microorganisms, was operated on a continuous feed basis for a period of more than 2 years. The results indicate that the biofilter medium with optimal moisture content of 68% and an effective bed retention time (EBRT) of 28.50s could degrade pyridine effectively (>99%) at a loading of 434 g pyridine m(-3)h(-1). The treated waste gas was also found to be free from pyridine odor.     

香菇多糖硫酸化衍生物的制备及其结构分析

采用改良的Ｗｏｌｆｒｏｍ方法制备了一系列的硫酸化香菇多糖衍生物。硫酸基含量测定结果表明,硫酸基的取代程序受反应时间和酯化试剂中氯磺酸与吡啶的比例的控制;证明甲基化分析方法不适合硫酸化香菇多糖衍生物的结构分析,＾１３Ｃ－ＮＭＲ数据表明,硫酸基取供在香菇多糖中Ｃ－６上,表明Ｃ－６位羟基的反应活性高于其他位置的羟基。     

4‐Fluorophenyl 3‐nitro‐2‐pyridinesulfenate as a practical protecting agent for amino acids

We report a new protecting agent ( 1 , Npys‐OPh(pF)) for 3‐nitro‐2‐pyridine (Npy) sulfenylation of amino, hydroxy, and thiol functional groups. Several Npys phenoxides were synthesized from Npys chloride (Npys‐Cl) and phenols in the presence of base in 1‐step reaction, and their ability for Npy‐sulfenylation was evaluated. As a result, 1 was selected as a new Npy‐sulfenylation agent with advantages including improved physicochemical stability, more controllable reactivity, and easier handling than the conventional protecting agent Npys‐Cl.     

The molecular structure of a complex of a 2,6-diimino-pyridine as a bidentate ligand with molybdenum carbonyl

Reaction of the pyridyl-diimine ligand, 2,6-[1- (2,2-dimethylpropanimino)ethyl]pyridine (1) with Mo(CO)₆ has unexpectedly yielded [Mo(CO)₄1], in which the normally tridentate ligand, even under forcing conditions, is bidentate. A single crystal X-ray structure determination reveals the distorted octahedral molecule with the MoC distances trans to the nitrogen donor atoms 0.1 Å shorter than the other two MoC distances. Other bond lengths suggest delocalization of charge in the chelate ring and this is reinforced by proton NMR data which suggests electron flow from the metal into the pyridine ring.     

Catalysis of imido group hydrolysis in a maleimide conjugate

Maleimides are often used for biomolecular conjugation with thiols. An underappreciated aspect of the imido group in a maleimide conjugate is its susceptibility to spontaneous hydrolysis, resulting in undesirable heterogeneity. Here, a chromophoric maleimide is used to demonstrate that both molybdate and chromate catalyze the hydrolysis of an imido group near neutral pH. Tungstate and 4-(dimethylamino)pyridine are less effective as catalysts. This work reveals a new mode of chemical reactivity for molybdate and chromate, and provides a strategy for decreasing the heterogeneity of bioconjugates derived from maleimides.     

可降解吡啶的全食副球菌B21-3的筛选鉴定及降解特性

【背景】吡啶作为一种难降解的有机污染物普遍存在于焦化、炼油、皮革和制药等行业的废水中,并对环境造成危害。【目的】治理废水中残留的有机污染物吡啶,筛选高效降解菌。【方法】采用富集培养和选择培养,以石家庄某污水处理厂的活性污泥为材料进行吡啶降解菌的筛选,通过形态特征、生理生化特性、(G+C)mol%测定及16S rRNA基因序列系统发育分析对筛选到的降解菌进行鉴定,并分析其对吡啶的降解特性。【结果】分离筛选到一株能以吡啶为唯一碳源和氮源生长代谢的降解菌B21-3,经鉴定该菌株为全食副球菌(Paracoccuspantotrophus)。菌株B21-3对吡啶的最适降解温度为32°C,最适降解pH为7.0,吡啶浓度为100mg/L时降解率为48.50%±0.02%;通过逐步提高吡啶初始浓度对菌株进行驯化,驯化后菌株可耐受较高浓度吡啶且吡啶降解率显著增加,吡啶浓度为100 mg/L时驯化后菌株B21-3对吡啶的降解率为90.26%±1.70%。驯化后菌株在含吡啶的无机盐平板上传代培养15代后,对吡啶的降解率为89.39%±2.03%。【结论】菌株B21-3具有较强的吡啶降解能力及降解稳定性,该菌株可作为吡啶污染水体生物修复的潜在资源。     

Electrochemical and EPR Characterization of 1,4-dihydropyridines. Reactivity Towards Alkyl Radicals

This work reports the electrochemical oxidation of a series of three synthesized 4-substituted-1,4-dihydropyridine derivatives in different electrolytic media. Also, an EPR characterization of intermediates and the reactivity of derivatives towards ABAP-derived alkyl radicals are reported. Dynamic, differential pulse and cyclic voltammetry studies on a glassy carbon electrode showed an irreversible single-peak due to the oxidation of the 1,4-dihydropyridine (1,4-DHP) ring via 2-electrons to the corresponding pyridine derivative. Levich plots were linear in different media, indicating that the oxidation process is diffusion-controlled. Calculated diffusion coefficients did not exhibit significant differences between the derivatives in the same medium. The oxidation mechanism follows the general pathway (electron, H + , electron, H + ) with formation of an unstable pyridinium radical. One-electron oxidation intermediate was confirmed with controlled potential electrolysis (CPE) and EPR experiments. On applying N-tert-butyl- &#102 -phenylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as the spin trap, these unstable radical intermediates from the oxidation of 1,4-DHP derivatives were intercepted. The final product of the CPE, i.e. pyridine derivative, was identified by GC-MS technique. Direct reactivity of the synthesized compounds towards alkyl radicals was demonstrated by UV-Vis. spectroscopy and GC-MS technique. Results indicate that these derivatives significantly react with the radicals, even compared with a well-known antioxidant drug such as nisoldipine.     

Electrochemical and EPR characterization of 1,4-dihydropyridines. Reactivity towards alkyl radicals

This work reports the electrochemical oxidation of a series of three synthesized 4-substituted-1,4-dihydropyridine derivatives in different electrolytic media. Also, an EPR characterization of intermediates and the reactivity of derivatives towards ABAP-derived alkyl radicals are reported. Dynamic, differential pulse and cyclic voltammetry studies on a glassy carbon electrode showed an irreversible single-peak due to the oxidation of the 1,4-dihydropyridine (1,4-DHP) ring via 2-electrons to the corresponding pyridine derivative. Levich plots were linear in different media, indicating that the oxidation process is diffusion-controlled. Calculated diffusion coefficients did not exhibit significant differences between the derivatives in the same medium. The oxidation mechanism follows the general pathway (electron, H+, electron, H+) with formation of an unstable pyridinium radical. One-electron oxidation intermediate was confirmed with controlled potential electrolysis (CPE) and EPR experiments. On applying N-tert-butyl-alpha-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as the spin trap, these unstable radical intermediates from the oxidation of 1,4-DHP derivatives were intercepted. The final product of the CPE, i.e. pyridine derivative, was identified by GC-MS technique. Direct reactivity of the synthesized compounds towards alkyl radicals was demonstrated by UV-Vis. spectroscopy and GC-MS technique. Results indicate that these derivatives significantly react with the radicals, even compared with a well-known antioxidant drug such as nisoldipine.     

Unexpected rearrangement of enantiomerically pure 3-aminoquinuclidine as a simple way of preparing diastereomeric octahydropyrrolo[2,3-c]pyridine derivatives

Reaction of (S)- or (R)-3-aminoquinuclidine with 2-chloropyrimidine or 2-bromopyrimidine led to an unexpected formation of both cis- and trans-octahydropyrrolo [2,3]pyridine derivatives. A single-step synthesis of two of the four stereoisomers of these octahydropyrrolo[2,3]pyridine derivatives provides a convenient way of generating stereochemically defined isomers. Optimization of reaction conditions was carried out by (1)H NMR monitoring. The relative and absolute stereochemistry of all four stereoisomers was determined by a combination of (1)H, (13)C, and (15)N NMR spectroscopy and vibrational circular dichroism spectroscopy.