Extraction procedure for the measurement of butyltin compounds in biological tissues using toluene, HBr, and tropolone.
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Acids↗
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N-phosphonoalkyl-5-aminomethylquinoxaline-2,3-diones: in vivo active AMPA and NMDA(glycine) antagonists.
N-Substituted 5-aminomethylquinoxalinediones containing carboxy or phosphonic acids yield potent and selective AMPA and/or NMDA (glycine-binding site) antagonists. Phosphonic acid derivatives are particularly water-soluble and display potent anticonvulsant effects in the electroshock-induced convulsion assay in mice.
Amino Acids↗
Some detoxification methods for N-nitrosamine-contaminated wastes.
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Acids↗
Laboratory decontamination and destruction of carcinogens in laboratory wastes: some N-nitrosamines.
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Acids↗
Cleavage and deprotection of peptides on MBHA-resin with hydrogen bromide.
Dilute hydrogen bromide in trifluoroacetic acid containing pentamethylbenzene and thioanisole was used in the cleavage and deprotection of peptides on MBHA-resin. Particular attention was paid to potential applicability of the method to kilogram scale synthesis of thymosin alpha 1. In the HPLC purification of the peptides, acetonitrile was replaced by relatively nontoxic isopropanol. The change should be economically and environmentally very attractive.
Acetates↗
Laboratory decontamination and destruction of carcinogens in laboratory wastes: some antineoplastic agents. International Agency for Research on Cancer.
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Acids↗
Selective detection of chlorine-containing compounds by gas chromatography/chemical reaction interface mass spectrometry.
Chemical reaction interface mass spectrometry (CRIMS) was studied as a gas chromatographic detection technique for chlorine-containing compounds. Both SO2 and HBr were tested as reactant gases. With SO2, a detection limit of 50 pg of diazepam and a linear range of 4 orders of magnitude were achieved, and the experimental data were reproducible. With HBr, the detection limit was 10 ng of diazepam and the linear dynamic range was only 2 orders of magnitude. The possible pharmacological application of CRIMS was studied using urine spiked with diazepam and several of its metabolites, and the results show CRIMS to be a simple but potentially powerful method in drug metabolism studies.
Acids↗
Infrared spectra of proton transfer complexes of the cycleanine alkaloid in solid state.
Proton transfer complexes obtained between the cycleanine alkaloid and hydrogen chloride, hydrogen bromide and nitric acids have been investigated by infrared spectroscopic technique between 4000 and 400 cm(-1) in KBr. The vibrational perturbations brought about by proton transfer complex formation, discussed in terms of preferred site of interaction, show that the proton of the inorganic acids is transferred to cycleanine through one of its N sites.
Alkaloids↗
Destruction of carcinogenic and mutagenic N-nitrosamides in laboratory wastes.
The chemical degradation of five N-nitrosamides used widely for the experimental induction of cancer has been studied with the goal of identifying, and experimentally validating, reliable methods that can be recommended for the destruction of carcinogenic N-nitrosoureas and related compounds in laboratory wastes. Although data are not yet complete, preliminary evidence indicates that none of the five methods studied thus far is ideal for hazard-control purposes. Decomposition with 1 mol/L potassium hydroxide solution destroyed the N-nitrosamides, but generated diazoalkanes, which are carcinogenic, toxic and potentially explosive. Treatment with strong acid in the presence of sulfamic acid or iron filings completely decomposed all N-nitrosamides without forming diazoalkanes, but failed in the presence of solvents which were immiscible with water. Cleavage with hydrogen bromide in glacial acetic acid proceeded to a point of maximum degradation, following which gradual reformation of the N-nitrosamide was observed; this resynthesis could be avoided by carefully bubbling nitrogen through the reaction mixture, but degradation was slow or failed completely in the presence of hydroxylic solvents. Permanganate oxidation was effective in sulfuric acid solution, but was incomplete when an alcohol or dimethyl sulfoxide was present. Salmonella typhimurium tester strains TA1535, TA1530 and TA100, which detect base-pair substitutions in DNA, detected mutagenic degradation products in each of the destruction methods, with the exception of the hydrobromic acid/acetic acid procedure.
Carcinogens↗
Commercial synthesis of alpha-D-cellobiosyl bromide heptaacetate.
A detailed commercial process for the synthesis and purification of the activated disaccharide, alpha-D-cellobiosyl bromide heptaacetate (1) was developed. Reaction of alpha-D-cellobiose octaacetate (CBO) with HBr in glacial acetic acid or in glacial acetic acid/methylene chloride combination affords alpha-D-cellobiosyl bromide heptaacetate in high yield and excellent quality. Process variables such as reaction solvent, reaction time, reaction temperature, HBr stoichiometry, isolation methods and product purification options were optimized for large-scale synthesis. alpha-D-Cellobiosyl bromide heptaacetate was successfully prepared in a commercial manufacturing plant.
Acetates↗
4-O-Acetyl-3-O-tert-butyldimethylsilyl-L-rhamnal: a building block in the stereoselective synthesis of 2-deoxy-alpha-L-rhamnopyranosides.
The stereoselective synthesis of 2-deoxy-alpha-L-glycosides by addition of various acceptors to 4-O-acetyl-3-O-tert-butyldimethylsilyl-L-rhamnal promoted by triphenylphosphine-hydrogen bromide is developed.
Glycosylation↗
Energy of hydrogen bonds probed by the adhesion of functionalized lipid layers.
It is now well admitted that hydrophobic interactions and hydrogen bonds are the main forces driving protein folding and stability. However, because of the complex structure of a protein, it is still difficult to separate the different energetic contributions and have a reliable estimate of the hydrogen bond part. This energy can be quantified on simpler systems such as surfaces bearing hydrogen-bonding groups. Using the surface force apparatus, we have directly measured the interaction energy between monolayers of lipids whose headgroups can establish hydrogen bonds in water: nitrilotriacetate, adenosine, thymidine, and methylated thymidine lipids. From the adhesion energy between the surfaces, we have deduced the energy of a single hydrogen bond in water. We found in each case an energy of 0.5 kcal/mol. This result is in good agreement with recent experimental and theoretical studies made on protein systems showing that intramolecular hydrogen bonds make a positive contribution to protein stabilization.
Energy Transfer↗
Fast microwave-assisted dansylation of N-nitrosamines. Analysis by high-performance liquid chromatography with fluorescence detection.
A fast microwave-assisted dansylation procedure has been developed for the derivatization of N-nitrosamines prior to high-performance liquid chromatography determination. N-Nitrosomorpholine, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine and N-nitrosopiperidine are first denitrosated by hydrobromic acid-acetic acid to produce secondary amines, which are then quantitatively dansylated in 5 min using radiation power of 378 W and a maximum pressure of 1.4 bar inside the reactor. The reaction mixture is separated on a C18 column with acetonitrile-water (55:45, v/v) as mobile phase with fluorimetric detection at 531 nm (excitation at 339 nm). The detection limits range from 8 to 75 pg for N-nitrosomorpholine and N-nitrosodiethylamine, respectively. The method was applied to study the recoveries of N-nitrosamines in beer and their determination in cigarette smoke.
Chromatography, High Pressure Liquid↗
Determination of N-nitrosamines in latex by sequential supercritical fluid extraction and derivatization.
A new method to determine N-nitrosamines in latex products has been developed by combination of supercritical fluids and chemical derivatization. A new design for a liquid trap has been introduced. A factorial fractional design was used in order to evaluate the influence of the different factors affecting the process. Factors such as pressure, temperature, static and dynamic time, restrictor temperature and volume of an hydrobromic acid-acetic anhydride mixture (1:10, v/v) were included in the design. CO2 was used as the extraction fluid. Gas chromatography with nitrogen and phosphorus sensitive detection was employed to achieve good sensitivity attending to the molecular structure of these compounds (N-nitrosamines and their corresponding secondary amines). The obtained results have shown to be useful to increase selectivity and reduce sample handling.
Chromatography, Gas↗
Determination of ethylene oxide by solid-phase microextraction device with on-fiber derivatization.
The solid-phase microextraction (SPME) device was used as a time-weighted average (TWA) sampler for ethylene oxide. Carboxen/polydimethylsiloxane (CAR/PDMS) fiber was used and hydrogen bromide (HBr) was loaded onto the fiber. The SPME fiber assembly was then inserted into PTFE tubing to improve the wearer's acceptance as a diffusive sampler. Known concentrations of ethylene oxide around the threshold limit values (TLVs)/time-weighted average and specific relative humidities (RHs) were generated by syringe pumps in a dynamic generation system. Ethylene oxide in gas bags were also generated. An exposure chamber was designed to allow measurement of face velocities, temperatures, exposing vapor concentrations, and RHs. Gas chromatography-mass spectrometry (GC-MS) was used for sample analysis. The appropriate adsorption time for SPME coating HBr was found to be 30 s and the desorption time for 2-bromothanol formed after sampling was determined to be 5 min. The experimental sampling constant of the sampler was found to be (2.96 +/- 0.09) x 10(-2) cm3/min, while face velocity (0-0.25 m/s) as well as RHs (10-80%) were not expected to have effects on the sampler.
Air Pollutants, Occupational↗
P(CH(3)NCH(2)CH(2))(3)N as a dehydrobromination reagent: synthesis of vitamin A derivatives revisited.
Although P(CH(3)NCH(2)CH(2))(3)N (1) was found to be less effective than 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in the removal of hydrogen bromide from vitamin A intermediates 13-cis-10-bromo-9,10-dihydroretinyl acetates (6) and 14-bromo-9,14-dihydroretinyl acetate (11) when the reaction was carried out in refluxing benzene, in acetonitrile at room temperature it was superior to DBN and DBU. A (31)P NMR study of this reaction suggests that the carbanion generated from acetonitrile-d(3) in the presence of 1 is the basic species that initiates the elimination step. Diastereoselectivity of the nucleophilic addition of (Z)-HC triple bond C(CH(3))=CHCH(2)OH to the carbonyl group of (E)-2-methyl-4-(2',6',6'-trimethyl-1'-cyclohexen-1'-yl)-3-butenal (2) was only moderate (20%), and (9R,10S)-13-cis-11,12-didehydro-9,10-dihydro-10-hydroxyretinol (3b) predominated. The LiAlH(4) reduction of the C triple bond C bond in the diastereoisomeric diols 3 afforded 13-cis-9,10-dihydro-10-hydroxyretinols 4a and 4b as major products together with 11-cis-13-cis-isomers and the deoxygenated compound (3EZ,5EZ,8E)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1,3,5,8-nonatetraene (9). Reaction of 15-acetates of the pure diastereoisomeric allylic alcohols 4a and 4b with PBr(3) occurred with significant but not identical retention of configuration, and with concomitant formation of the rearranged bromide 11.
Bridged Bicyclo Compounds, Heterocyclic↗
Photodissociation of HBr. 1. Electronic structure, photodissociation dynamics, and vector correlation coefficients.
Ab initio potential energy curves, transition dipole moments, and spin-orbit coupling matrix elements are computed for HBr. These are then used, within the framework of time-dependent quantum-mechanical wave-packet calculations, to study the photodissociation dynamics of the molecule. Total and partial integral cross sections, the branching fraction for the formation of excited-state bromine atoms Br(2P(1/2)), and the lowest order anisotropy parameters, beta, for both ground and excited-state bromine are calculated as a function of photolysis energy and compared to experimental and theoretical data determined previously. Higher order anisotropy parameters are computed for the first time for HBr and compared to recent experimental measurements. A new expression for the Re[a1(3) (parallel, perpendicular)] parameter describing coherent parallel and perpendicular production of ground-state bromine in terms of the dynamical functions is given. Although good agreement is obtained between the theoretical predictions and the experimental measurements, the discrepancies are analyzed to establish how improvements might be achieved. Insight is obtained into the nonadiabatic dynamics by comparing the results of diabatic and fully adiabatic calculations.
Anisotropy↗
Synthetic studies on the trans-chlorocyclopropane dienyne side chain of callipeltoside A.
[structure] Enantiomerically enriched trans-chlorocyclopropanemethanol was obtained by lipase kinetic resolution of dichlorocyclopropanemethanol 3, followed by reduction. The sp-sp(2) bond of the trans-chlorocyclopropane dienyne side chain of callipeltoside A was constructed via a Stille coupling reaction of 1, 1-dibromo-1-alkene 7 and a vinylstannane in a highly dipolar solvent capable of promoting HBr elimination to give internal alkynes.
Animals↗