Haloaldehyde polymeres XIII. Polydibromofluoroacetaldehyde

Dibromofluoracetaldehyde (DBFA) was prepared by reducing methyl dibromofluoroacetate with lithium aluminium hydride (LAH) at low temperatures whereby theLAH was added to dibromofluoroacetate. The initially obtainedDBFA hydrate was dehydrated to the free aldehyde. Methyl dibromofluoroacetate was synthesized together with methyl bromodifluoroacetate by air oxidation of 1,1-dibromo-2,2-difluoroethylene. The mixture of oxidation products, consisting of two acid halides, was treated with methanol and gave a mixture of the methyl esters which here separated by distillation. DBFA was polymerized with anionic and cationic initiators to crystalline insoluble poly-DBFA. Poly-DBFA degraded quantitatively at elevated temperatures to monomericDBFA. Copolymerization ofDBFA with chloral gave copolymers with nearly the same comonomer composition as the feed.DBFA was also copolymerized with phenyl isocyanate to a copolymer which contained acetal and urethane linkages.Part XII:R. W. Campbell, andO. Vogl, Makromolekulare Chemie, in press.     

Model Construction for the A–B–C Ring System of Lysergic Acid via Vilsmeier–Haack‐Type Cyclization of 1H‐Indole‐4‐propanoic Acid Derivatives

Vilsmeier–Haack‐type cyclization of 1H‐indole‐4‐propanoic acid derivatives was examined as model construction for the A–B–C ring system of lysergic acid ( 1 ). Smooth cyclization from the 4 position of 1H‐indole to the 3 position was achieved by Vilsmeier–Haack reaction in the presence of K₂CO₃ in MeCN, and the best substrate was found to be the N,N‐dimethylcarboxamide 9 (Table 1). The modified method can be successfully applied to an α‐amino acid derivative protected with an N‐acetyl function, i.e., to 27 (Table 2); however, loss of optical purity was observed in the cyclization when a chiral substrate (S)‐ 27 was used (Scheme 5). On the other hand, the intramolecular Pummerer reaction of the corresponding sulfoxide 20 afforded an S‐containing tricyclic system 22 , which was formed by a cyclization to the 5 position (Scheme 3).     

Time-temperature transformation (TTT) cure diagram of an unsaturated polyester resin

The curing of an unsaturated polyester resin was studied by differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), and Fourier-transform infrared spectroscopy (FTIR). The results are presented in the form of a time-temperature-transformation (TTT) diagram. The kinetic analysis was performed by means of the dynamic Ozawa method. This analysis was used to determine the curing times (t) at various conversions (α) and temperatures (T) (isoconversional lines ln t = A + E/RT). The equivalence of the Ozawa method and the isothermal isoconversional adjustment ln t = A + E/RT were demonstrated. The relationship between the glassy transition temperature (T_g) and the conversion α was determined by DSC. It was established that this relationship is one-to-one and independent of mass, initiation system, and curing temperature (T_c). The T_g-α relationship was adjusted using the DiBenedetto equations and heat capacity data. Using the T_g-α relationship and the isoconversional lines, the vitrification curve was determined and it was observed that the vitrification times obtained are consistent with those obtained experimentally when T_c = T_g. Gelation was determined by TMA, the material being considered gelled when it reached sufficient mechanical stability for the TMA measuring probe to become embedded in it. At that moment the conversion reached was determined by DSC. It was seen that the material always gels at constant conversion, regardless of the curing temperature. The gelation line (gel times) were traced from the corresponding isoconversional line. © 1997 John Wiley & Sons, Inc.     

Differentiation of essential oils in Atractylodes lancea and Atractylodes koreana by gas chromatography with mass spectrometry

Atractylodes rhizome is a valuable traditional Chinese medicinal herb that comprises complex several species whose essential oils are the primary pharmacologically active component. Essential oils of Atractylodes lancea and Atractylodes koreana were extracted by hydrodistillation, and the yield was determined. The average yield of essential oil obtained from A. lancea (2.91%) was higher than that from A. koreana (2.42%). The volatile components of the essential oils were then identified by a gas chromatography with mass spectrometry method that demonstrated good precision. The method showed clear differences in the numbers and contents of volatile components between the two species. 41 and 45 volatile components were identified in A. lancea and A. koreana, respectively. Atractylon (48.68%) was the primary volatile component in A. lancea, while eudesma‐4(14)‐en‐11‐ol (11.81%) was major in A. koreana. However, the most significant difference between A. lancea and A. koreana was the major component of atractylon and atractydin. Principal component analysis was utilized to reveal the correlation between volatile components and species, and the analysis was used to successfully discriminate between A. lancea and A. koreana samples. These results suggest that different species of Atractylodes rhizome may yield essential oils that differ significantly in content and composition.     

GC–MS characterisation and antibacterial activity evaluation of Nigella sativa oil against diverse strains of Salmonella

Salmonella resistance is becoming a worldwide serious health issue in these days; therefore, it is an urgent need to develop some alternative approaches to overcome this problem. Twenty bacterial strains were isolated and purified from different environmental sources and confirmed as Salmonella by morphological and biochemical analyses. Further confirmation was done by 16s rRNA sequencing. Antibiotic susceptibility test was performed by well diffusion assay against different concentrations of Ceftriaxone and Ciprofloxacin. The behaviour of both antibiotics was different against diverse strains of Salmonella. Salmonella strains resistant to both antibiotics were analysed for antibacterial activity of natural extracts of Nigella sativa (black seeds). N. sativa oil was found to be more effective against Salmonella species for which even Ceftriaxone and Ciprofloxacin were ineffective. Gas chromatography and mass spectrometry analysis of N. sativa oil was also accomplished, exhibiting 10 compounds including thymoquinone, p-cymene, cis-carveol, thymol, α-phellandrene, α-pinene, β-pinene, trans-anethole, α-longipinene and longifolene.     

Thermal stability of para- and ortho-isomers of tris-decyl-(ethyl-benzyl)-ammonium chloride

Thermal stability of para (p--) and ortho (o-) isomers was investigated by CRTG and reaction kinetic analysis. The temperature started the mass decrease of o-isomer was about 20°C lower than that of p-isomer by CRTG. The activation energies of thermal decomposition of o- and p-isomers were 136.9 and 153.4 kJ mol^–1, respectively. The effect of steric hindrance on heat of formation was calculated by AM1 method using Win MOPAC3.0 for the model compound of p- and o-isomers. The lower stability of o-isomer was the results of the steric hindrance between the ethylene unit of aromatic ring and three alkyl chains.     

Synthesis of 2-[3-(trifluoromethyl)phenyl]furo[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridine derivatives

2-[3-(Trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (I) was prepared by a three-step synthesis. Its reaction with phosphorus sulfide rendered thione II which was methylated to 2-[3-(Trifluoromethyl)phenyl]-4-methylsulfanylfuro[3,2-c]pyridine (III). 5-Methyl-2-[3-(trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (IV) was obtained by the reaction of I with methyl iodide in PTC conditions. The chlorine atom in derivate V was replaced with heterocyclic secondary amines via nucleophilic substitution and 4-substituted furopyridines VIa and VIb were thus prepared. 2-[3-(Trifluoromethyl)phenyl]furo[3,2-c]pyridine-4-carboxylic acid (VII) was obtained by hydrolysis of the corresponding carbonitrile Va.     

环糊精与两种有机物的包合物的不同光解特性

The effectiveness of the solubilization and photodegradation of β-cyclodextrin （β-CD） and hydroxypropyl-β- cyclodextrin （HPCD） on two hydrophobic organic compounds （HOC） of methyl parathion and pentachlorophenol was investigated. The results indicate that the solubilization or photodegradation of two HOC were influenced by complexing with β-CD or HPCD. The solubility of pentachlorophenol （PCP） was increased linearly with β-CD concentration. The solubility of methyl parathion （MPT） was increased with the increase of β-CD concentration initially, however, as the β-CD concentration was enhanced above 3 g/L, the solubility was decreased with increase of β-CD concentration. The solubilities of two HOC were increased linearly with the increase of HPCD concentration. Although the photodegradation of MPT was improved, the photodegradation of PCP was restrained by complexation of HOC with β-CD or HPCD. In a word, the effectiveness of photodegradation or solubilization of HPCD was more significant than that of β-CD. One potential application of such a method was the in situ remediation of hydrophobic organic pollutants in contaminated soil and groundwater or industrial waste streams.     

Synthesis of 4-substituted 1,4-benzodiazepine-3,5-diones

Synthetic routes leading to the preparation of 4-substituted 1,4-benzodiazepine-3,5-diones are described. Thus, 2-carbobenzoxyaminobenzoic acid was converted to its p-nitrobenzyl ester (I) and the decarbobenzoxylated product (II) gave, with ethyl α-bromoacetate, N-(2-carboxy p-nitrobenzylate)phenylglycine ethyl ester (III). The latter was hydrogenolyzed to N-(2-car-boxy)phenylglycine ethyl ester (IV), which was coupled with benzylamine to give N-(2-carboxy-benzylamido)phenylglycine ethyl ester (VIa). Saponification of VIa afforded N-(2-carboxy-benzylamido)phenylglycine (VIIa) which was cyclized with DCCI to produce 4-benzyl-2H-1,4-benzodiazepine-3,5(lH,4H)dione (VIIIa). Alternatively, 2-nitro-N-phenylbenzamide (Xb) was reduced to 2-amino-N-phenylbenzamide (XIb) which was converted to N-(2-carboxanih'do)-phenylglycine ethyl ester (VIb). The latter was converted to 4-phenyl-2H-1,4-benzodiazepine-3,5(1H,4H)dione (VIIIb) in an analogous fashion described for VIIIa.     

Stereoselective synthesis and 2D NMR study of S-D-glucopyranoside

2, 3, 4-Tri-O-benzyl-6-O trimethylsilyl-α-D-glucopyranosyl bromide reacted with RSH compounds (R = Et, t-Bu, PhCH₂, p-PhBu^t, Ph, 2-benzoxazole, 2-benzothiazole), with diisopropylethylamine as base, to give S-D-glucosides. The α- and β- anomeric ratio was dependent on the pKa. value of the thiol compound. If pKa value was less than or equal to 7, β-anomer was obtained. If pKa value was equal to or more than 11, α anomer was obtained. If pKa value was between 9 and 10.6, a mixture of α- and β-anomer was obtained. The probable mechanism was discussed. The chemical shifts of proton and carbon in these S-D-glucosides were measured and verified by 2D NMR (cosy and hetcor).     

Study of structural parameters on the adsorption selectivity of a molecularly imprinted polymer

This work was focused on the influence of match degree of structure parameters i.e. molecular size, volume and polarity (denoted as R_d, V_d and P_d) between imprinted cavities in Qu-MIP and Xn on the adsorption selectivity. The results presented that the influence of R_d on the adsorption selectivity was the largest and the most regular, while the influence of P_d was the smallest and the most irregular. Besides, the influence degree of V_d was decreased in general with the increase of R_d. However, as R_d was in the threshold of [0.99, 1.02], V_d would rise to the major influence factor. Furthermore, utilizing data obtained from experiment, the influence authority of R_d, V_d and P_d on the adsorption selectivity was calculated theoretically through multiple linear regression and principal component analysis of IBM SPSS Statistics 20, and results showed the authority order was R_d, V_d and P_d at any circumstance despite the value was different, which was in accordance with the result we directly inducted from the experiment.     

Formation of the main degradation compounds from arabinose,xylose, mannose and arabinitol during pyrolysis

The thermochemical behaviour of sugars (D- and DL-arabinose, D- and DL-xylose and D-mannose) and sugar alcohol (D- and DL-arabinitol) was investigated by TG and pyrolysis-gas chromatography with mass-selective detection (Py-GC/MSD). The temperature of pyrolysis was 500 and 550°C. The TG-curves were measured both in air and nitrogen atmospheres, from 25 to 700°C with the heating rate of 2°C min^-1. In each case, the main pyrolysis products were classified into the following compound groups: (i) furanes, (ii) pyranes, (iii) cyclopentanes, (iv) cyclohexanes, (v) anhydroglucopyranoses, (vi) dianhydroglucopyranoses and (vii) saturated fatty acids. For example, the main peaks of the chromatograms of pentoses (arabinose, xylose), hexose (mannose) and sugar alcohols (arabinitols) were different. The greatest peak of pentoses in gas-chromatogram was 2-furancarboxaldehyde and that of hexose was (2H)-furan-3-one. The greatest peak of arabinitols at pyrolysis temperature of 500°C was furan methanol and at 550°C a-angeligalactone. 5-hydroxymethyl-2-furan carboxaldehyde was found only in the pyrolysis of D-mannose (hexose). The former study showed that it was not found in pyrolysis of pentoses. The amount of CO₂ and H₂O was not determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

TLC densitometric quantification of picrosides (picroside-I and picroside-II) in Picrorhiza kurroa and its substitute Picrorhiza scrophulariiflora and their antioxidant studies

Picroside‐I and picroside‐II are known bioactive metabolites in Picrorhiza species. In the present study a simple, precise method has been established for the simultaneous determination of picrosides (picroside‐I and picroside‐II) in two different Picrorhiza species, P. kurroa and P. scrophulariiflora. This method was also validated for accuracy, precision, robustness, limit of detection and quantification, repeatability and recovery, according to International Conference of Harmonization guidelines. Separation and quantification was achieved by HPTLC using as the mobile phase chloroform–methanol (88:12, v/v) on precoated silica gel 60F₂₅₄ aluminum plates. Densitometric determination was carried out at wavelength λ_max 254 nm in UV absorbance mode. Comparative study also revealed that picroside‐I and picroside‐II are higher in P. scrophulariiflora than P. kurroa. Picroside‐I content was found to be 1.258 and 1.611%, and picroside‐II was estimated as 0.481 and 0.613% in P. kurroa and P. scrophulariiflora, respectively. Antioxidant potential of these two Picrorhiza species was also studied using DPPH. At a concentration of 0.1 mg/mL the scavenging activities of P. kurroa and P. scrophulariiflora were found to 37.70 and 34.30%, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Temperature Effect on Drying and Swelling of Kappa Carrageenan Gels: A Steady State Fluorescence Study

Summary: A novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling of κ- carrageenan (kappa carrageenan) gels at various temperatures. κ- carrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in κ- carrageenan and used as a fluorescence probe. Scattered light intensities, I_sc and fluorescence intensities, I were monitored during the drying and swelling of κ- carrageenan gels. It was observed that the fluorescence intensity decreased linearly as drying time was increased. A simple model consisting of Case II diffusion was used to quantify the drying processes of the κ- carrageenan gels. This moving boundary model provided packing constant, k₀. During swelling, fluorescence intensity increased exponentially as time is increased. The increase in I, was modeled using Li-Tanaka equation from which swelling time constants, τ_c and cooperative diffusion coefficients, D_c were determined. It was observed that swelling time constants, τ_c decreased and diffusion coefficients, D_c increased as the swelling temperature was increased. Activation energies for drying and swelling were also obtained and found to be 53.9 and 47.2 kJ mol⁻¹, respectively.     

Totalsynthese und absolute Konfiguration von natürlichem Multifloramin

The diphenol 1 was resolved into its antipodes and their absolute configuration was established. The levorotatory isomer R-(?)- 1 was oxidized to the dienone R-(?)- 6 , which was rearranged to afford natural (?)-multifloramine (R-(?)- 7 ), thus establishing that the latter has the R-configuration. By the same reaction sequences, the enantiomeric diphenol S-(+)- 1 was transformed to provide (+)-multifloramine (S-(+)- 7 ) of the S-configuration.     

Asymmetric Synthesis of (R)-Fluoxetine: A Practical Approach Using Recyclable and in-situ Generated Oxazaborolidine Catalyst

A practical route for the synthesis of (R)-fluoxetine•HCl (ee＝96%) in 56% overall yield was described. The key intermediate (R)-3-chloro-1-phenyl-1-propanol was obtained by the asymmetric reduction of prochiral 3-chloropropiophenone using in-situ generated oxazaborolidine catalyst derived from (S)-α,α-diphenylprolinol. The chiral procatalyst (S)-α,α-diphenylprolinol was recovered quantitatively and recycled. An improved practical synthesis of (S)-α,α-diphenylprolinol was also discussed.     

Optimized Method for the Determination of Flavonoid Glycosides and Aglycones

The relationship R_M=f (log % S; S- modifier) of several flavonoids and their sugar derivatives was examined by using chromatographic systems chosen by preliminary experiments. The dependence for flavonoid aglycones was flat in the whole mobile phase concentration. Two types of the R_M=f (log % S) plots, related to the size of sugar molecule, were found. For glycosides with smaller sugar moiety (arabinose or glucose) the plot was almost parallel, while plots of derivatives with larger sugar moiety (rutose) were convergent. After plotting the relationship R_M=f (log % S), even if standards are not available, it is possible to qualify the examined compound as containing single or complex sugar moiety. For all mentioned above compounds the R_M=f (log %S) values were given. Silica gel Si60 was used as polar adsorbent. Mobile phase composition was determined in preliminary experiments; it was composed of two solvents: methanol in ethyl acetate in increasing concentration of methanol: 5 – 20%.     

Amino Acid Derivatives,IV [1]: Synthesis and Antiviral Evaluation of New α-Amino Acid Esters Bearing Methyl β-<Emphasis Type="SmallCaps">d</Emphasis>-Ribofuranoside Side Chain

Summary. Methyl 2,3-O-isopropylidene-β-d-ribofuranoside was synthesized and oxidized with HIO₄ to afford the corresponding carboxylic acid. The latter was coupled with the appropriate acylated amino acids in the presence of HOBt and DDC as coupling reagents to give the corresponding amides. The methyl acetate derivative was hydrolyzed with 2 N KOH/MeOH to the corresponding carboxylic acid, which was coupled with l-glycine methyl ester to furnish the amide. Deprotection was carried out with 70% AcOH at reflux temperature. The prepared glycopeptides were tested for antiviral activity against Herpes Simplex virus type-1 (HSV-1) and hepatitis-A virus (HAV). The plaque reduction infectivity assay was used to determine virus count reduction as a result of treatment with tested compounds.     

Direct chiral separation of abscisic acid by high-performance liquid chromatography with a phenyl column and a mobile phase containing γ-cyclodextrin

Abscisic acid (2-cis,4-trans-abscisic acid) is a plant hormone that has an asymmetric carbon atom. We tried to separate the enantiomers of native abscisic acid by HPLC using a phenyl column and a chiral mobile phase containing γ-cyclodextrin. The optimum mobile phase conditions were found to be 0.8% (w/v) γ-cyclodextrin, 4% (v/v) acetonitrile, and 20 mM phosphate buffer (pH 6.0). It was found that (R)-abscisic acid was earlier detected than (S)-abscisic acid. Since γ-cyclodextrin is hardly retained on a phenyl column, it was suggested that (R)-abscisic acid formed a more stable complex with γ-cyclodextrin than the (S)-abscisic acid. Abscisic acid in an acacia honey sample was successfully enantioseparated with the proposed method and only (S)-abscisic acid was detected. A biologically inactive 2-trans,4-trans-abscisic acid, which was prepared by irradiation of abscisic acid with a light-emitting diode lamp at 365 nm, was partially enantioseparated by the proposed method. Since the irradiation of (S)-abscisic acid-induced cis-to-trans isomerization to produce one 2-trans,4-trans-abscisic acid enantiomer, it is reasonable that racemization did not proceed during the cis-to-trans isomerization. (S)-Abscisic acid and probably (S)-2-trans,4-trans-abscisic acid were detected in a honey sample, where the peak area of (S)-abscisic acid was 7 times larger than that of (S)-2-trans,4-trans-abscisic acid.