Synthesis and characterization of copolymers from 4-halo(chloro, bromo) salicylic acid

Copolymers have been prepared by condensing a mixture of either 4-chloro or 4-bromosalicylic acid and any one of the comonomer like salicylic acid,p-hydroxybenzoic acid,p-aminosalicylic acid,p-aminobenzoic acid,p-cresol andp-halo(chloro, bromo)phenol with formaldehyde in the presence of 5M H₂SO₄. Copolymer composition of each of the copolymer has been estimated on the basis of halogen content and/or on the basis of results of non-aqueous titrations of the copolymer against standard sodium methoxide and/or tetra-n-butylammonium hydroxide. The IR spectral characteristics of copolymers have been noted. The viscometric and thermal studies of copolymers have also been carried out.     

TYPE I AND TYPE II MECHANISMS IN THE PHOTOSENSITIZED LYSIS OF PHOSPHATIDYLCHOLINE LIPOSOMES BY HEMATOPORPHYRIN

Abstract The lysis of phosphatidylcholine (PC) liposomes was sensitized to visible light (>500nm) by hematoporphyrin (HP) incorporated in the liposomes (0.09-1.5%, wt/wt) or in the external buffer (1-15 μM). The lytic mechanism changed from the Type II pathway mediated by singlet oxygen (¹O₂) at low HP concentrations to the anoxic, Type I pathway at high HP concentrations. Spectral measurements of HP in aqueous and organic solvents indicate that the HP was not aggregated (monomers and/or dimers) for Type II sensitization and aggregated for Type I conditions. High concentrations of azide (>0.1 M) or DABCO (>0.5 M) were protective with high HP concentration under oxic and anoxic conditions, which cannot involve the scavenging of ¹O₂. Feasible protective mechanisms are quenching of the HP triplet state by high azide and repair of the damaged membrane by DABCO via an electron transfer process. There was significant protection against lysis under Type I conditions by low concentrations of ferricyanide (>1 mM), indicative of an electron transfer mechanism. The incorporation of 22 mol % cholesterol in PC liposomes with 1% HP had no effect on the lytic efficiency for oxic and anoxic conditions. Dipalmitoylphosphatidylcholine liposomes incorporating 1% HP showed negligible photosensitized lysis at 50°C compared with PC liposomes with 1% HP at 25°C. The promotion of photosensitized lysis by hydrodynamic agitation observed in prior work with methylene blue (Grossweiner and Grossweiner, 1982) was significant with HP sensitization for both Type I and Type II conditions. Actinometry with PC liposomes incorporating 1% HP indicated that photosensitized lysis was very inefficient, requiring many absorbed quanta per lysed liposome. Preliminary experiments with crude hematoporphyrin derivative (Hpd) showed similar concentration effects on lytic efficiency, where PC liposomes incorporating 0.1% (wt/wt) Hpd were strongly sensitized by oxygen, whereas sensitization by oxygen was insignificant with 3.1% Hpd. The results with HP and crude Hpd indicate that lytic damage in a biomembrane does not necessarily require oxygenation.     

Diisophorone and related compounds. Part 17 synthesis and nucleophilic reactions of 4,8-dibromodiisophorones

4,8-Dibromodiisophor-2(7)-en-l-ol-3-one is obtained by dibromination of the parent ketol, or by monobromination of the 4- or 8-bromo-analogues. It is converted, byKoch-Haaf carboxylation, into 4,8-dibromodiisophor-2(7)-en-3-one-1-carboxylic acid, which is also accessible by bromination of the appropriate preformed diisophorone-1-carboxylic acids. The existence of the dibromoketol in two stereoisomeric forms is traced to conformational differences of its 4-substituent.Acetolysis of the 4,8-dibromo-1-carboxylic acid or its methyl ester occurs exclusively at the 8-position, but hydrazinolysis removes both halogen substitutents, with formation of 4-hydrazono-diisophorones. The¹³C-nmr spectra reflect the structural and conformational changes. A general fragmentation pattern accounts for the behaviour of the individual compounds under electron impact.

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Diisophoron und verwandte Verbindungen. 17. Mitt. Synthese und nucleophile Reaktionen von 4,8-Dibromdiisophoronen

Zusammenfassung 4,8-Dibromdiisophor-2(7)-en-l-ol-3-on wird durch Dibromierung des Stamm-Ketols oder durch Monobromierung seiner 4- oder 8-Monobrom-Derivate erhalten. MittelsKoch-Haaf Carboxylierung wird es in die entsprechende 1-Carbonsäure umgewandelt, die auch durch Bromierung von vorgebildeten Carbonsäuren zugänglich ist. Stereoisomere Formen des Dibromketols unterscheiden sich durch die Konformation ihres 4-Substituenten.Die Acetolyse der 4,8-Dibrom-1-carbonsäure beschränkt sich auf ihren 8-Substituenten; Hydrazinolyse entfernt hingegen beide Halogen-Atome unter Bildung von 4-Hydrazono-diisophoronen. Die¹³C-Kernresonanz-Spektren stimmen mit den Struktur- und Konfigurations-Änderungen überein. Das massenspektrometrische Verhalten der verschiedenen Verbindungen wird an Hand eines allgemeinen Fragmentations-Schemas erörtert.

     

Diisophorone and related compounds. Part 13 Nucleophilic reactions of 8-bromodiisophorone-1-carboxylic acid

8-Bromo-1-carboxydiisophor-2(7)-en-3-one is obtainable from diisophorone by successive monobromination andKoch-Haaf carboxylation, performed in either sequence. Nucleophilic replacement of its 8-bromo-substituent by acetolysis or methanolysis occurs with simultaneous migration, resulting in the 4-acetoxy- or 4-methoxy-compounds, respectively. In contrast, alkaline hydrolysis yields the 8-hydroxy-compound as main-product; this serves as the precursor of 3,8-diketodiisophor-2(7)-ene-1-carboxylic acid. The configuration of the 4- and 8-substituents is tentatively assigned on the basis of i.r. spectral data.

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Diisophoron und verwandte Verbindungen, 13. Mitt.: Nucleophile Reaktionen von 8-Bromdiisophoron-1-carbonsäure

Zusammenfassung 8-Brom-1-carboxydiisophor-2(7)-en-3-on ist aus Diisophoron durch Monobromierung undKoch-Haaf-Carboxylierung zugänglich; die Reaktionen sind in beliebiger Reihenfolge ausführbar. Nucleophiler Austausch des 8-Brom-Substituenten durch Acetolyse und Methanolyse erfolgt unter gleichzeitiger Isomerisierung, wobei 4-Acetoxy- oder Methoxy-Verbindungen entstehen. Im Gegensatz dazu liefert alkalische Hydrolyse hauptsächlich die 8-Hydroxyl-Verbindung; diese dient als Ausgangsmaterial für die Darstellung der 3,8-Diketodiisophor-2(7)-en-1-carbonsäure. Vorläufige Konfigurationen der 4- und 8-Substituenten werden auf Grund von IR-Spektren vorgeschlagen.

     

Selective extraction of antioxidants with molecularly imprinted polymers

Molecular imprinting technology can be used to generate specific artificial polymeric receptors, i.e., high affinity stationary phases, as already shown for peptides and many other food ingredients. In this work, polymers have been molecularly imprinted with three exemplary antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG). Results of chromatographic evaluations are presented, demonstrating the specificity of the imprinted polymers (MIP) compared to non-specific control polymers (CP). For a BHA imprinted polymer and the respective analyte BHA a separation factor of α=k_BHA-MIP′/k_CP′=1.12 was found, whereas for the BHT-MIP a higher selectivity was determined with α=k_BHT-MIP′/k_CP′=1.47. Using the PG selective MIP for PG as analyte a value of α=k_PG-MIP′/k_CP′=1.24 could be achieved. Furthermore, results of extraction procedures based on MIP and CP phases are presented, demonstrating for instance a higher selectivity of the BHA-MIP in comparison with its CP when using methanol or acetonitrile as analyte solvent, and of the PG-MIP when performing the extraction in acetonitrile.     

Structure, thermodynamics, and liquid-vapor equilibrium of ethanol from molecular-dynamics simulations using nonadditive interactions

We present a molecular-dynamics simulation study of the bulk and liquid-vapor interfacial properties of ethanol using a polarizable force field based on the fluctuating charge (FQ) formalism, as well as the nonpolarizable CHARMM22 force field. Both models are competitive with respect to the prediction of ambient liquid properties such as liquid density, enthalpy of vaporization, dielectric constant, and self-diffusion constants. The polarizable model predicts an average condensed-phase dipole moment of 2.2 D associated with an induced liquid-phase dipole moment of 0.6 D; though qualitatively in agreement with earlier nonadditive models as well as recent Car-Parinello calculations, the current FQ model underestimates the condensed-phase dipole moment. In terms of liquid structure, both models are in agreement with recent neutron-diffraction results of liquid ethanol structure, although the polarizable model predicts the hydroxyl-hydrogen-hydroxyl-hydrogen structure factor in closer agreement with the experimental data. In terms of interfacial properties, both models predict ambient surface tension to within 4% of the experimental value of 22.8 dyncm, while overestimating the surface excess entropy by almost a factor of 2. Both models display the characteristic preferential orientation of interfacial molecules. The polarizable model allows for a monotonic variation of the average molecular dipole moment from the bulk value to that of the vapor phase. Consequently, there is a dramatic difference in the surface potential predicted by the polarizable and nonpolarizable models. The polarizable model estimates a surface potential of -209+/-3 mV, while the nonpolarizable model yields a value of -944+/-10 mV. Finally, based on the vapor-liquid equilibrium simulation data from several temperatures, we estimate the critical properties of both models. As observed with other FQ models for associating fluids (such as water and methanol), and counter to what one would anticipate by modeling more physically the electrostatic response to local environment, the current FQ model underestimates the critical temperature and overestimates the critical density of ethanol; moreover, the FQ model is, in this respect, equivalent to the underlying fixed-charge model. These results further suggest the need to revisit polarizable models in terms of quantitative vapor-liquid equilibrium prediction.     

MALDI post-source decay and LIFT-TOF/TOF investigation of α-cyano-4-hydroxycinnamic acid cluster interferences

Large signals from alpha-cyano-4-hydroxycinnamic acid (CHCA) matrix complexes with sodium and potassium ions were found to interfere with sensitive matrix-assisted laser desorption/ionization (MALDI) analysis of a hydrochloric acid digest of gelatine preparations. The nature of some selected matrix clusters was investigated by conventional post-source decay and LIFT-TOF/TOF experiments. The matrix clusters fragmented readily by neutral evaporation to give smaller sized matrix cluster species without matrix disintegration. Their characterization distinguished them from peptide signals, in particular from those that had the same nominal mass and differed only in the fractional part of the mass as encountered for gelatine-derived peptides. Knowledge of the molecular composition of these cluster species allowed using them for internal calibration of the MALDI mass spectra. The hydrolytic peptides could be analyzed with increased sensitivity when using 2,5-dihydroxy benzoic acid (DHB) as the MALDI matrix.     

Synthesis of 4,5-diaryl-1H-pyrazole-3-ol derivatives as potential COX-2 inhibitors

4,5-Diaryl-1H-pyrazole-3-ol was utilized as a versatile template to synthesize several classes of compounds such as pyrazolo-oxazines 7, pyrazolo-benzooxazines 9, pyrazolo-oxazoles 10, and its analogues 11a-c as potential COX-2 inhibitors. Compounds 11b,c were successfully synthesized with use of pyridinium p-toluenesulfonate mediated cyclization of the ketal intermediate. Diaryl-pyrazolo-benzooxazepine analogues were synthesized by using Cu-mediated cyclization of the O-alkylated arylbromide intermediate. Arylsulfonamides were synthesized efficiently on a large scale with 4-[4-(4-fluorophenyl)-5-hydroxy-2H-pyrazol-3-yl]benzenesulfonamide 31 template readily synthesized from commercially available 4-sulfamoyl benzoic acid 29. The structure of a representative compound from each class was confirmed by X-ray crystallography. Selected compounds tested for inhibitory activity against COX-1 and COX-2 enzymes showed good selectivity for COX-2 versus COX-1 enzyme.     

Determination of antimony in rain water at the nanogram level with surfactant and brilliant green

A new, simple, selective and sensitive method for the spectrophotometric determination of antimony in rain water is described. It includes preconcentrating Sb with surfactants (i.e. cetylpyridinium chloride (CPC) and Triton X-100 (TX-100)) into toluene and allowing the extract to react with a dye, i.e. brilliant green (BG). The value of apparent molar absorptivity is 5.55 × 10⁵ L-mol^–1· cm^–1 at λ_max = 620 nm; the detection limit is 3 ng/mL Sb in rain water at 3-fold preconcentration. Received: 6 June 1997 / Revised: 1 August 1997 / Accepted: 5 August 1997     

Small molecule matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using a polymer matrix

We have employed a light-absorbing electrically conductive polymer as a matrix to determine the molecular mass of small organic molecules using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. This method, which is in contrast to the usual MALDI strategy for matrix selection in which a small molecule matrix is used with a high molecular mass analyte, addresses the problem of matrix interference which limits the usefulness of MALDI-TOF for small molecule analysis. Use of negative ion mode offers advantages for this application. Using this approach, we have obtained clean molecular ion mass spectra of small organic molecules in the mass range 100-300 Da.