1-(Bromoacetyl)pyrene,a novel photoinitiator for the copolymerization of styrene and acrylonitrile

A comparative study on photoinitiated solution copolymerization of Styrene (Sty), with acrylonitrile (AN) using pyrene, 1-acetylpyrene, and 1-(bromoacetyl)pyrene (BrPy) as initiators, showed that the introduction of a chromophoric moiety, bromoacetyl (–COCH₂Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of Sty with AN (Sty–co–AN) using BrPy as photoinitiator has been studied in detail. The kinetic data, inhibiting effect of benzoquinone, and electron spin resonance (ESR) studies suggest that the polymerization proceeds via a free radical mechanism. The system followed non-ideal kinetics (R _p α[BrPy]^0.7[Sty]^1.09[AN]^1.01) and degradative solvent transfer reasonably explained these kinetic non-idealities. The co-monomer reactivity ratios calculated by using the Finemann–Ross and Kelen–Tudos models were r ₁ (Sty) = 0.39 and r ₂ (AN) = 0.05. The reactivity ratios strongly indicate that the two monomers enter in almost alternating arrangement along the copolymer chain.     

强致突变物二硝基苯并(a)芘的合成、结构与致突变性研究

本文通过苯并(a)芘与HNO3的亲电取代反应, 合成了两个新化合物二硝基苯并(a)芘异构体。用HPLC分离、分析了产物, 并用IR、^1H NMR、MS和HRMS谱研究了其结构, 证明产物为1,6-二硝基苯并(a)芘(1)和3,6-二硝基苯并(a)芘(2)。短期生物试验──Amos试验结果表明两个异构体均为强直接致突变物。     

(22S)-6-O-acetyl-21betaH-hopane-3beta,6beta,22,29-tetrol from oakmoss (Evernia prunastri)

A novel hopanoid triterpene, (22S)-6-O-acetyl-21betaH-hopane-3beta,6beta,22,29-tetraol, was isolated from oakmoss (Evernia prunastri (L.) Ach.), as identified from 1H, 13C, DEPT, COSY, NOESY, HSQC and HMBC NMR, MS and IR spectroscopy. During recrystallisation a new compound, 30-nor-6-O-acetyl-3beta,6beta-dihydroxy-21alphaH-hopan-22-one, was formed by a formal loss of methanol from the dihydroxypropyl moiety. No biological activity was found for the naturally occurring compound upon testing against a series of fish and human pathogenic bacteria.     

The characterization of (+/-)-anti-benzo[a]pyrene diolepoxide-DNA adducts and (+/-)-anti-dibenzo[a,l]pyrene diolepoxide--DNA adducts in the same DNA sample using solid-matrix phosphorescence

Solid-matrix phosphorescence (SMP) spectra and lifetimes were used to characterize the (±)-anti-benzo[a]pyrene diolepoxide [(±)-anti-B[a]PDE] and (±)-anti-dibenzo[a,l]pyrene diolepoxide [(±)-anti-DB[a,l]PDE] bonded to the same sample of DNA. SMP spectra and lifetimes were also acquired for two samples of DNA that had only (±)-anti-B[a]PDE or (±)-anti-DB[a,l]PDE bonded to the individual samples of DNA. A detailed comparison of the SMP properties was made among the three samples of DNA. The SMP excitation spectra for the (±)-anti-B[a]PDE-DNA and the (±)-anti-DB[a,l]PDE-DNA adducts were very similar. However, the SMP emission spectra of the two DNA adduct systems were very dissimilar with a major emission band for the (±)-anti-B[a]PDE-DNA adducts appearing at 613 nm and for the (±)-anti-DB[a,l]PDE-DNA adducts a major band was at 558 nm. It was possible to selectively use SMP emission wavelengths and obtain a SMP excitation of spectrum of the (±)-anti-DB[a,l]PDE-DNA adducts in the dual adducted DNA sample without the (±)-anti-B[a]PDE-DNA adducts emitting SMP. In addition, it was shown that the SMP emission spectrum of the dual adducted DNA sample could be used to detect both adduct systems in the modified DNA sample. It was demonstrated that the SMP lifetimes could be effectively employed to characterize the dual adducted DNA sample. For example, the SMP decay curve for the (±)-anti-DB[a,l]PDE-DNA adducts could be acquired without any SMP emission from the (±)-anti-B[a]PDE-DNA adducts. Also, ln(SMP intensity) versus time plots were very useful in characterizing the dual adducted DNA sample.     

Synthesis,Crystal Structure and Characterization of 6-(p-tolyl)-6-H-Decachlorobenzo[cd]pyrene

A new perchlorinated fused compound, 6-(p-tolyl)-6H-decachloro-benzo[cd]-pyrene 1, was synthesized with solvothermal reaction,a novel approach developed in our group. 1 is an interesting molecule for it is similar in structure to chlorinated fragment molecules of fullerenes^[1]. Besides, its homologues such as 6-methyl-6H-benzo[cd]pyrenes, 6-methoxycarbonyl-6H-benzo[cd]pyrene and 6-mesyloxyl-6H-benzo[cd]pyrene[2] have been synthesized as parent hydrocarbons of benzo[cd]pyrenyl system, which were investigated for its NBMO properties^[3].     

The equilibrium constants of cadmium(II)-, lead(II)-, magnesium(II)-, and zinc(II)-alpha,beta,gamma,delta-tetrakis(1-methylpyridinium-4-yl)porphine complexes

The equilibrium constants of alpha,beta,gamma,delta-tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) complexes of cadmium(II), lead(II), magnesium(II), and zinc(II) were spectrophotometrically determined using the absorption spectra at the Soret band and the fluorescence spectra. The values of the following constants at 25 degrees C and ionic strength 0.1M were evaluated: K(PbP) = 10(-8.07 +/- 0.09), K(CdP) = 10(-7.68 +/- 0.03), K(ZnP) = 10(1.72 +/- 0.08), and K(MgP) = 10(-7.40 +/- 0.08) by the acid hydrolysis reaction of the TMPyP-metal complex at various pHs; K(PbP) = 10(-7.80 +/- 0.04) and K(CdP) = 10(-7.38 +/- 0.04) were determined by the ligand exchange reaction between TMPyP and nitrilotriacetic acid.     

Polyelectrolyte effects on the quenching of pyrene fluorescence in solutions of a pyrene substituted poly(acrylic acid)

The quenching of pyrene fluorescence by nitromethane, Tl⁺, Cu²⁺, I^?, and 4-dimethylaminopyridine (DMAP) in aqueous solutions of a pyrene substituted poly(acrylic acid) ( 1 ) was influenced by the “polyelectrolyte effect” of 1 . The efficiency of quenching in solutions of 1 was measured in terms of the Stern–Volmer constants for dynamic and static quenching which were obtained from comparison of the intensity and lifetime of pyrene fluorescence in solutions of 1 and a monomer model compound. The efficiency of quenching in solutions of 1 was always greater at high pH ( 9 ) in comparison to that at low pH ( 4 ). The ionization of carboxylic groups in 1 caused an expansion of the polymer mainchain and concomitant exposure of the pyrene molecules to the aqueous phase and quencher. The polyanion domain of 1 favored the condensation of cationic quenchers and could account for very efficient quenching in case of Cu²⁺ and Tl⁺. A very efficient quenching of pyrene fluorescence in solutions of 1 by DMAP at high pH was attributed to the hydrophobic interactions of DMAP and pyrene moiety. The iodide ions were less efficient quenchers of pyrene fluorescence due to electrostatic repulsion from the polyanion. The efficiency of quenching by nitromethane was not significantly affected by ionization of the carboxylic groups in 1 .     

A convenient new route to piperidines, pyrrolizidines, indolizidines, and quinolizidines by cyclization of acetylenic sulfones with beta and gamma-chloroamines. Enantioselective total synthesis of indolizidines (-)-167B, (-)-209D, (-)-209B, and (-)-207A

The methyl esters of (L)-phenylalanine and (L)-methionine underwent conjugate additions via their free amino groups to 1-(p-toluenesulfonyl)hexyne, followed by intramolecular acylation of the corresponding enamide anions and tautomerization to afford 2-benzyl-5-n-butyl-3-hydroxy-4-(p-toluenesulfonyl)pyrrole and 5-n-butyl-3-hydroxy-2-(2-methylthioethyl)-4-(p-toluenesulfonyl)pyr role, respectively. The conjugate additions of a series of acyclic and cyclic secondary beta- and gamma-chloroamines to acetylenic sulfones proceeded similarly under mild conditions. The resulting adducts were deprotonated with LDA in THF at -78 degrees C, and the resulting sulfone-stabilized carbanions underwent intramolecular alkylation to afford cyclic enamine sulfones. Thus, acyclic gamma-chloroalkyl-benzylamines afforded the corresponding 2- or 2,6-disubstituted piperidines, while 2-(chloromethyl)pyrrolidines, 2-(2-chloroethyl)pyrrolidines, 2-(chloromethyl)piperidines, and 2-(2-chloroethyl)piperidines produced the corresponding 3-substituted pyrrolizidines, 5- or 3-substituted indolizidines, and 4-substituted quinolizidines, respectively. 8-Methyl-5-substituted indolizidines were also prepared from the appropriate methyl-substituted chloroamine precursor. Enantioselective syntheses were achieved by employing chiral chloroamines derived from amino acids or other enantiopure precursors. Further transformations of several of the products provided concise syntheses of four dendrobatid alkaloids. Thus, reduction of (8aS)-5-n-propyl-6-(p-toluenesulfonyl)-delta5,6-indolizidine with sodium cyanoborohydride in trifluoroacetic acid, followed by reductive desulfonylation, afforded (-)-indolizidine 167B. The corresponding 5-n-hexyl derivative similarly produced (-)-indolizidine 209D, while (-)-(8R, 8aS)-8-methyl-5-n-pentyl-6-(p-toluenesulfonyl)-delta5,6-indo lizidine furnished (-)-indolizidine 209B. Finally, the similar reduction and debenzylation of (-)-(8R,8aS)-5-(2-benzyloxyethyl)-8-methyl-6-(p-toluenesulfo nyl)-delta5,6-indolizidine produced the corresponding 5-hydroxyethyl indolizidine. This was subjected to chlorination of the alcohol group with thionyl chloride and substitution with a higher order allyl cuprate reagent to afford (-)-indolizidine 207A.     

Determination of pyrene and benzo(a)pyrene residues in water by derivative synchronous solid-phase spectrofluorimetry

Benzo(a)pyrene (BaP) and pyrene (Pyr) are two polycyclic aromatic hydrocarbons (PAHs) showing native fluorescence in solution. Both compounds have been determined in water at trace levels by solid-phase spectrofluorimetry, in which BaP and Pyr are fixed on Sephadex G-25 gel and the relative fluorescence intensity is measured after the system is packed in a 1-mm silica cell. First-derivative synchronous spectra obtained at =38 nm were used to determine BaP and Pyr in the presence of other potentially interferent PAHs. The spectral characteristics of the PAHs-gel system are described, the applicable concentration ranges being 0.4–2.5 ng/ml for BaP and 0.7–4.5 ng/ml for Pyr. The relative standard deviations were 1.1% and 1.4% for BaP and Pyr respectively. The detection limits were 0.04 ng/ml for BaP and 0.1 ng/ml for Pyr. The method was applied to the analysis of both compounds in water at trace levels and a recovery study on tap, natural and sea waters was carried out.     

Nephrotoxicity assessments of benzo(a)pyrene during zebrafish embryogenesis

Benzo(a)pyrene is a chemical produced during the process of making fried, roasted, and smoked foods. It remains unclear whether benzo(a)pyrene affects the early development of human organs. In this study, we used the transgenic zebrafish line Tg(wt1b:GFP) as a model to assess benzo(a)pyrene-induced kidney malformation. By soaking zebrafish embryos in benzo(a)pyrene at various doses (2, 20, and 200 ppb), only a minor effect on the survival rate was detected (0 ppb: 97.8 ± 1.9 %; 2–200 ppb: 89.1 ± 5.8–91.5 ± 8.3 %). However, benzo(a)pyrene significantly affected the development of the kidney (malformation rates ranges from 50.0 ± 3.5 to 77.4 ± 5.3 %). Various abnormalities, such as unusual curving of pronephric tubes, swollen glomerulus, and incomplete development of pronephric ducts, were observed. This study provides a rapid and effective protocol for the evaluation of the notable effects of benzo(a)pyrene on embryonic kidney development.     

苯并(a)芘的分离与检测研究进展

苯并(a)芘已经被确认为是一种具有高强度的致癌性、致畸性及致基因突变性的稠环芳烃,同时又具有较高的稳定性和隐匿性等特点。苯并(a)芘的存在对环境和人体健康等都产生严重的影响。本文对苯并(a)芘的性质、来源及致病机理进行了详细的介绍,总结了在食品、煤沥青、药材、化妆品以及环境等领域中苯并(a)芘的分离与检测方法,并对苯并(a)芘的分离与检测进行了展望。     

Asymmetric syntheses of the homalium alkaloids (-)-(s,s)-homaline and (-)-(r,r)-hopromine

The highly diastereoselective conjugate additions of the novel lithium amide reagents lithium (R)-N-(3-chloropropyl)-N-(α-methylbenzyl)amide and lithium (R)-N-(3-chloropropyl)-N-(α-methyl-p-methoxybenzyl)amide to α,β-unsaturated esters were used as the key steps in syntheses of the homalium alkaloids (-)-(S,S)-homaline and (-)-(R,R)-hopromine. The asymmetric synthesis of (-)-(S,S)-homaline was achieved in 8 steps and 18% overall yield, and the asymmetric synthesis of (-)-(R,R)-hopromine was achieved in 9 steps and 23% overall yield, from commercially available starting materials in each case. These syntheses therefore represent by far the most efficient total asymmetric syntheses of these alkaloids reported to date. A sample of the (4'R,4'S)-epimer of hopromine was also produced using this approach, which provided the first unambiguous confirmation of its absolute configuration and therefore that of natural (-)-(R,R)-hopromine.