Occupational exposure to low levels of organic and inorganic substances in a chemical plant for the production of terephtalic acid dimethyl ester

The aim of our study was the evaluation of personal exposure to chemical pollutants in workers employed in a plant for the production of terephtalic acid dimethyl ester. Chemical agents have been included in the monitoring program on the basis of the industrial process. In the plant, the oxidation of p-xylene is performed by air and the resulting acid is esterified with methyl alcohol. Purified terephtalic acid dimethyl ester is then utilized for the production of polyethylene terephtalate. The environmental monitoring included terephtalic acid dimethyl ester, p-toluic acid methyl ester, terephtalic acid, p-xylene, methylacetate, methylbenzoate, formic acid, acetic acid, methanol, and the catalysts cobalt acetate and manganese (II) acetate tetrahydrate. Personal exposure to the cited airborne substances was performed in the breathing zone of six workers. Air samplings were carried out by drawing air through glass fibre filters (terephtalic acid dimethyl ester, p-toluic acid methyl ester and terephtalic acid aerosols), by active adsorption (methanol, formic and acetic acids vapours). p-Xylene, methylacetate and methylbenzoate vapours were collected by passive sampling. Cellulose nitrate filters were used for cobalt and manganese salts samplings. Analyses were performed by UV detection high-performance liquid chromatography (terephtalic acid dimethyl ester, p-toluic acid methyl ester and terephtalic acid), flame ionization detection gas chromatography (p-xylene, acetic acid methyl ester and benzoic acid methyl ester), ion chromatography (formic and acetic acids) and inductively coupled plasma-mass spectrometry (cobalt and manganese). The results were evaluated according to the threshold limit values (TLVs) of the American Conference of Governmental Industrial Hygienists (ACGIH) and indicated that the environmental levels of the workplace pollutants were well below the threshold limit values-time weighed average (TLV-TWA) adopted by the American Conference of Governmental Industrial Hygienists for 2002, although for three substances the TLVs were not available.     

Three New ent‐Trachylobane Diterpenoids from Co‐cultures of the Calli of Trewia nudiflora and Fusarium sp. WXE

Five diterpenoids, including three new ent‐trachylobane diterpenoids, i.e., (3α)‐3‐hydroxy‐ent‐trachylobane‐17,19‐dioic acid 19‐methyl ester ( 1 ), ent‐trachylobane‐17,19‐dioic acid 19‐methyl ester ( 2 ), ent‐trachylobane‐17,19‐dioic acid ( 3 ), and two known atisane‐type ones, i.e., (16α)‐16,17‐dihydroxy‐ent‐atisan‐19‐oic acid methyl ester ( 4 ), and 17‐hydroxy‐ent‐atisan‐19‐oic acid methyl ester ( 5 ), were isolated from the co‐culture extract of the calli of Trewia nudiflora and its endophytic fungus Fusarium sp. WXE. Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR experiments, and HR‐Q‐TOF mass spectrometry. The antitumor and antibacterial properties of the new compounds were evaluated.     

中药龟板提取物化学成分及其调控鼠骨髓间充质干细胞(rMSCs)增殖活性的实验研究

中药龟板提取物浸膏经硅胶柱层析, 用石油醚-乙酸乙酯作洗脱剂, 梯度洗脱, 得到16个组分; 采用MTT法和流式细胞技术研究了它们对鼠骨髓间充质干细胞(rMSCs)的增殖作用, 实验结果显示组分Ts-12具有促进rMSCs增殖的作用(p＜0.05), 而组分Ts-4则表现出抑制rMSCs增殖的作用(p＜0.05), 其它样品对rMSCs的增殖作用不显著(p＞0.05), 不具统计学意义. 采用了GC-MS分析各组分化学成分, 并用HPLC和9个标准物质鉴定确证了组分Ts-12中含有十六酸甲酯(S-1)、十六酸乙酯(S-3)、十八酸甲酯(S-4)和甾醇(S-7)以及十四酸甾醇酯(S-8), 组分Ts-4主要含有十八酸(S-5). 对标准品也采用了MTT法和流式细胞仪研究了它们对rMSCs的增殖作用, 结果表明十四酸甾醇酯和十六酸甲酯具有促进rMSCs增殖的作用, 而十八酸具有抑制作用.     

Fragmentation of trimethylsilyl derivatives of 2-alkoxyphenols: A further violation of the ‘even-electron rule’

The mass spectra of trimethylsilyl (TMS) ethers of 2-methoxyphenols show abundant [M–30]⁺˙ ions originating from consecutive loss of two methyl radicals. This is illustrated by comparison of the accurate mass-measured and linked-scan spectra of the TMS derivatives of 2-methoxyphenol (guaiacol), 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid methyl ester (ferulic acid methyl ester) with those of the TMS derivatives of phenol, 4-hydroxybenzaldehyde, 3-(4-hydroxyphenyl)-2-propenoic acid methyl ester (p-coumaric acid methyl ester), 3-methoxyphenol and 4-methoxyphenol. This distinctive ortho effect is valuable in the identification of isomeric phenolic compounds. In the spectra of the TMS derivatives of 2-ethoxyphenol and 2-propoxyphenol the sequential loss of two radicals is less pronounced, because elimination of the side-chain and a methyl group with rearrangement and hydrogen migration is competitive.     

Secoiridoid Constituents from the Fruits of Ligustrum lucidum

Four new secoiridiod glucosides, p‐hydroxyphenethyl 7‐β‐D ‐glucosideelenolic acid ester ( 1 ), 6′‐elenolylnicotiflorine ( 2 ), 6′′′‐acetylnicotiflorine ( 3 ), and oleoside 7‐ethyl 11‐methyl ester ( 4 ), as well as six known glucosides, nuezhenide ( 5 ), Gl‐3 ( 6 ), nicotiflorine ( 7 ), isonuezhenide ( 8 ), neonuezhenide ( 9 ), and oleoside 11‐methyl ester ( 10 ) were isolated from the fruits of Ligustrum lucidum. Their structures were elucidated by spectroscopic methods. Compound 4 was an artifact produced during extraction.     

A new triterpenoid saponin and other saponins from <Emphasis Type="Italic">Salicornia europaea</Emphasis>

A new triterpenoid saponin, 3β,29-dihydroxy-olean-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester (1), together with four known triterpenoid saponins, i.e., oleanolic acid 28-O-β-D-glucoside (2), chikusetsusaponin IVa methyl ester (3), calenduloside E (4), and calenduloside E 6'-methyl ester (5), was isolated from Salicornia europaea Linn. Their structures were elucidated on the basis of spectral analysis.     

A New 30‐Noroleanane Saponin from Wedelia chinensis

A novel 30‐nortriterpenoid saponin, (3β)‐3‐hydroxy‐30‐noroleana‐12,20(29)‐dien‐28‐oic acid 3‐(β‐D ‐glucopyranosiduronic acid 6‐methyl ester) ( 1 ), and a known compound, (3β)‐oleanolic acid 3‐(β‐D ‐glucopyranosiduronic acid 6‐methyl ester) ( 2 ), were isolated from the aerial parts of Wedelia chinensis. The structures were established by their spectral data including ¹H‐ and ¹³C‐NMR, ¹H,¹H‐COSY, HMBC, HSQC, NOESY, and HR‐FAB‐MS data.     

Deoxy-nitrosugars. 16th Communication. Synthesis of N-acetyl-4-deoxyneuraminic acid

The synthesis of 5-acetamido-4-deoxyneuraminic acid ( 1 ) is described. Acetylation of a mixture of the epimeric triols 4 and 5 gave the tetraacetates 7 and 8 (Scheme 1). Ozonolysis of a mixture of these acetates followed by base-promoted β-elimination led to the (E) -configurated α,β-unsaturated keto ester 10 , which was hydrogenated to give the saturated keto ester 11 . Saponification of 11 and hydrolytic removal of the benzylidene group followed by anion-exchange chromatography gave the 5-acetamido-4-deoxyneuraminic acid ( 1 , Scheme 1 and 2). De-O-acetylation (NaOMe/MeOH) of the keto ester 11 gave a mixture of the tert-butyl ester 12 and the methyl ester 13 , which were converted to tert-butyl N-acetyl-4-deoxyneuraminate ( 14 ) and to methyl N-acetyl-4-deoxyneuraminate ( 15 ), respectively. Hydrogenolysis of the benzylidene acetal 11 followed by de-O-acetylation gave the pentahydroxy ester 16 .     

Reactions of 2-isocyanatobenzoyl chloride and 2-carbomethoxyphenyl isocyanate with 5-aminotetrazole

Treatment of 2-isocyanatobenzoyl chloride ( 4 ) with 5-aminotetrazole (5-AT) gave 3-(5-tetrazolyl)quinazoline-2,4(1H,3H)-dione ( 1 ) directly. Treatment of 2-carbomethoxyphenyl isocyanate ( 5 ) with 5-AT gave 2-[((5-amino-1H-tetrazol-1-yl)carbonyl)amino]benzoic acid methyl ester ( 6 ) as a kinetic product, which was thermally isomerized to 2-[((1H-tetrazol-5-ylamino)carbonyl)amino]benzoic acid methyl ester ( 7 ), the thermodynamically more stable urea. Cyclization of 7 with polyphosphoric acid gave 2-(1H-tetrazol-5-ylamino)-4H-3,1-benzoxazin-4-one ( 2 ). Urea 6 was quite labile in solution, as shown by nmr, and readily reacted with methanol to give 2-[(methoxycarbonyl)amino]benzoic acid methyl ester ( 10 ).     

Organic Base‐Catalyzed Stereoselective Isomerizations of 4‐Hydroxy‐4‐phenyl‐but‐2‐ynoic Acid Methyl Ester to (E)‐ and (Z)‐4‐Oxo‐4‐phenyl‐but‐2‐enoic Acid Methyl Esters

We have developed a 1,4‐diazabicyclo[2.2.2]octane (DABCO)‐catalyzed isomerization of 4‐hydroxy‐4‐phenyl‐but‐2‐ynoic acid methyl ester to (E)‐4‐oxo‐4‐phenyl‐but‐2‐enoic acid methyl ester and an N,N‐diisopropylethylamine‐catalyzed isomerization of the same substrate to (Z)‐4‐oxo‐4‐phenyl‐but‐2‐enoic acid methyl ester.     

Three New Sesquiterpenoids from Echinops ritro L.

From the whole plants of E. ritro L., the three new sesquiterpenoids (3α,4α,6α)‐3,13‐dihydroxyguaia‐7(11),10(14)‐dieno‐12,6‐lactone ( 1 ), (3α,4α,6α,11β)‐3‐hydroxyguai‐1(10)‐eno‐12,6‐lactone ( 2 ), and (11α)‐11,13‐dihydroarglanilic acid methyl ester (=(4β,6α,11α)‐4,6‐dihydroxy‐1‐oxoeudesm‐2‐en‐12‐oic acid methyl ester; 3 ), together with eight known sesquiterpenoids, were isolated. Their structures were elucidated through analysis of spectroscopic data including extensive 2D‐NMR.     

Solvent Effects on the Protonation Constants of Some <Emphasis Type="Italic">α</Emphasis>-Amino Acid Esters in 1,4-Dioxane–Water Mixtures

The stoichiometric protonation constants of some α-amino acid esters (glycine methyl ester, glycine t-butyl ester, l-valine methyl ester, l-valine ethyl ester, l-valine t-butyl ester, l-serine methyl ester, l-serine ethyl ester, l-leucine methyl ester, l-leucine ethyl ester, l-leucine t-butyl ester, l-alanine methyl ester, l-alanine benzyl ester, l-phenylalanine methyl ester, l-phenylalanine ethyl ester, and l-phenylalanine t-butyl ester) in water and 20%, 40%, and 60% (v/v) 1,4-dioxane–water mixtures have been determined at an ionic strength of 0.10 mol⋅L⁻¹ NaCl and at 25.0±0.1 °C under a nitrogen atmosphere. A potentiometric method was used and the calculation of the protonation constants has been carried out using the BEST computer program. The results were discussed in terms of macroscopic properties of the mixed solvent. The stoichiometric protonation constants were influenced by changes in solvent composition and their variations were discussed in terms of preferential solvation. Also, knowledge the protonation constant of α-amino acid esters will be helpful when determining the microscopic equilibrium constants of their corresponding amino acids.     

Characterization and purification of polyunsaturated fatty acids from microalgae by gas chromatography-mass spectrometry and countercurrent chromatography

Summary The present study was undertaken in order to characterize then to purify fatty acids from marine phytoplankton. From a crude mixture of fatty acid methyl esters it was possible to isolate by countercurrent chromatography a mixture of four polyunsaturated fatty acid methyl ester identified as being hexadecatrienoic acid methyl ester, octadecatetraenoic acid methyl ester, eicosapentaenoic acid methyl ester and docosahexaenoic acid methyl ester by gas chromatography coupled with mass spectrometry in electron impact and in positive-ion chemical ionization mode. The four polyunsaturated fatty acids are in different ratios in mixtures from the two microorganisms:Skeletonema costatum andIsochrysis galbana.     

Pd(II)-catalyzed vinylic polymerization of norbornene and copolymerization with norbornene and copolymerization with norbornene carboxylic acid esters

The vinylic polymerization of norbornene and its copolymerization with norbornene carboxylic acid methyl esters were investigated. Norbornene was polymerized by us using di-μ-chloro-bis-(6-methoxybicyclo[2.2.1]hept-2-ene-endo-5σ,2π)-palladium(II) as catalyst. The polymerization time can be decreased by a factor of 100000 by activation of the catalyst with methylaluminoxane (MAO). With this palladium catalyst activated by MAO, 140 t of norbornene can be polymerized per mol palladium per h. This catalyst system was much more active than [Pd(CH₃CN)₄](BF₄)₂ ( I ). The polymerization of norbornene by (6-methoxybicyclo[2.2.1]hept-2-ene-endo-5σ,2π)-palladium(II) tetrafluoroborate was also possible but it was not as fast as the polymerization by Pd catalysts activated with MAO. We were also able to obtain copolymers of norbornene and 5-norbornene-2-carboxylic acid methyl ester (exo/endo = 1/4 or 2/3) containing between 15 and 20 mol-% ester units. The copolymerization of norbornene and 2-methyl-5-norbornene-2-carboxylic acid methyl ester (exo/endo = 7/3) was faster than the copolymerization mentioned before. In contrast the homopolymerization of 2-methyl-5-norbornene-2-carboxylic acid methyl ester was 10 times slower than that of 5-norbornene-2-carboxylic acid methyl ester (exo/endo = 1/4).     

Ring‐opening metathesis polymerization of amino acid‐functionalized norbornene derivatives

Amino acid‐derived novel norbornene derivatives, N,N′‐(endo‐bicyclo[2.2.1] hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐alanine methyl ester (NBA), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐leucine methyl ester (NBL), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐phenylalanine methyl ester (NBF) were synthesized and polymerized using the Grubbs 2nd generation ruthenium (Ru) catalyst. Although NBA, NBL, and NBF did not undergo homopolymerization, they underwent copolymerization with norbornene (NB) to give the copolymers with M_n ranging from 5200 to 38,100. The maximum incorporation ratio of the amino acid‐based unit was 9%, and the cis contents of the main chain were 54–66%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5337–5343, 2006     

A new helvolic acid derivative from an endophytic Fusarium sp. of Ficus carica

A new helvolic acid derivative named helvolic acid methyl ester (1), together with two known helvolic acid compounds, helvolic acid (2) and hydrohelvolic acid (3), were isolated from the fermentation of endophytic fungus Fusarium sp. in Ficus carica leaves. Their structures were elucidated and identified by spectroscopic methods. Compounds 1–3 showed potent antifungal and antibacterial activities.     

Synthesis of unsymmetric bile pigments: Mesobilirubin-VIIIα, 17-desvinyl-17-ethyl-bilirubin-VIIIα and 12-despropionic acid-12-ethyl-mesobilirubin-XIIIα

The unnatural bile pigments 17-desvinyl-17-ethylbilirubin-VIIIα, mesobilirubin-VIIIα and 12-despropionic acid-12-ethyl mesobilirubin-XIIIα were synthesized via (1) “reverse scrambling” of bilirubin-XIIIα or mesobilirubin-IXα with mesobilirubin-IVα or etiobilirubin-IV-γ or (2) following coupling of xanthobilirubic acid methyl ester with ψ-xanthobilirubic acid methyl ester, or coupling of xanthobilirubic acid methyl ester with kryptopyrromethenone.     

Synthesis of 4,5-dihydro-4-methyl-1-phenyl-1,4,5-benzotriazocine-2,3,6(1H) triones

The title compounds, 7a and its 9-chloro analog 7b , were prepared in three steps from methyl N-phenylanthranilates. Thus, methyl N-phenylanthranilate ( 3a ) was treated with oxalyl chloride to yield 2-[(2-chloro-1, 2-dioxoethyl) phenylamino]benzoic acid methyl ester ( 4a ). Treatment of 4a with methylhydrazine gave 2-([2-(1-methylhydrazino)-1,2-dioxoethyl]phenylamino) benzoic acid methyl ester ( 6a ), which was cyclized with sodium hydride in dimethylformamide to produce 7a . Alkylation of 7a and 7b with iodomethane afforded the respective 5-methyl derivatives 8a and 8b . A survey of the known literature benzotriazocines is presented.     

Carbazole-substituted dehydroalanine main chain polymers. Synthesis and characterization of poly[methyl 2-(9-carbazolyl) acetylaminopropenoate] and poly[2-(9-carbazolyl) acetylaminopropenoic acid]

The preparation and radical-initiated polymerization of a carbazole-substituted N-acylated dehydroalanine, namely, 2-(9-carbazolyl)acetylaminopropenoic acid ( 7 ) and its methyl ester ( 6 ) is reported. The monomers 6 and 7 were prepared by dehydrochlorination of N-acylated β-chloroalanine derivatives. The monomer model compounds for the two polymers, namely, 2-(9-carbazolyl)acetylamino-2-methylpropanoic acid ( 11 ) and its methyl ester ( 10 ), were also prepared. The polymers and their monomer model compounds were characterized by elemental analysis, IR and ¹H-NMR spectra. The polymers 12 and 13 of different molecular weights could be obtained by changing the monomer-to-initiator ratios used in polymerization experiments.     

Clionasterol Glucoside and Acylated Clionasterol Glucosides from Oplismenus burmannii

A new clionasterol glucoside, clionasterol‐[(1'→3α)‐O‐β‐D]‐glucopyranoside ( 1 ), a new acylated clionasterol glucoside, clionasterol‐[6'‐O‐acyl‐(1'→3β)‐O‐b‐D]‐glucopyranoside ( 2 ) and clionasterol ( 3 ) were isolated from the aerial parts of Oplismenus burmannii. The nature and length of fatty acid acyl chains in 2 was identified by alkaline methanolysis of compound 2 . The aglycone fraction on GC‐MS analysis showed three peaks in GC at t_R 49.86 (82.1%), 51.13 (13.3%) and 56.53 (4.6%) min, which were characterized as arachidic acid methyl ester ( a ) oleic acid methyl ester ( b ) and 12‐methyltetradecanoic acid methyl ester ( c ) respectively. Thus 2 was characterized as a mixture of three new compounds, clionasterol‐[6'‐O‐eicosanoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2a ), clionasterol‐[6'‐O‐(8Z)‐octa‐deca‐9‐enoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2b ) and clionasterol‐[6'‐O‐(12‐methyltetradecanoyl)‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2c ).