Acta chemica Scandinavica. Series B: Organic chemistry and biochemistry最新文献

Levels of ethene and propene, together with those of some other light hydrocarbons (propane, butane, isobutane and ethyne), have been measured under realistic conditions in environmental tobacco smoke (ETS) as a step towards the elucidation of the sources of 2-hydroxyethyl and 2-hydroxypropyl adducts of hemoglobin observed in non-smokers. These adducts may reflect in vivo doses of carcinogenic epoxides that are metabolites of the respective alkenes. The data show that 2.0 mg ethene, 1.4 mg propene, and 0.7 mg propane together with smaller amounts of butane, isobutane and ethyne are released per cigarette smoked (0.66 g tobacco) of a common Swedish brand. The alkenes in ETS should be considered as contributing factors to a risk of systemic cancer from passive smoking. With regard to alkene intake, even a relatively mild exposure to ETS (2 cigarettes per h for 5 h per day in a 33 m3 room with one air change per hour is estimated to correspond to the active smoking of about one cigarette per day.

When 1-anilino-8-naphthalenesulfonate (ANS) interacts with phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) its fluorescence is enhanced and a blue shift occurs. There is evidence that ANS binds to the site of the nucleotide substrate. The work described herein shows that when various anion inhibitors are added to the ANS-enzyme solution, de-enhancement of the fluorescence occurs. Extrapolation to infinite anion concentration shows that pyruvate ions are the most effective quenchers (ca. 90%) and nitrate ions the least effective, sulfate and phosphate ions being intermediate. The results are consistent with earlier enzymes kinetic findings suggesting that pyruvate ions and ANS, both competing with the nucleotide substrate, are able to bind to the enzyme simultaneously and that sulfate, phosphate and nitrate ions can, to various extents, affect the properties at the active centre of phosphoglycerate kinase via conformational changes without sharing ligands with the nucleotide substrate.

A new synthesis of 4-methoxy-2,3,5-trimethylpyridine (2), an important building block for the preparation of gastric-acid inhibiting compounds, is described. Condensation of ethyl 3-amino-2-methyl-2-butenoate (3) and diethyl 2-methylmalonate (4) gives 4-hydroxy-3,5,6-trimethyl-2(1H)-pyridone 5. Reaction of 5 with phosphoryl chloride affords 2,4-dichloro-3,5,6-trimethylpyridine (9a), which, upon hydrogenolysis with palladium on charcoal, gives 2,3,5-trimethylpyridine (10). However, selective hydrogenolysis in acidic solution yields 4-chloro-2-3-5-trimethylpyridine (11). Substitution of the chlorine in 11 with methoxide ion gives 4-methoxy-2,3,5-trimethylpyridine (2), which can be oxidized to the corresponding N-oxide (13). This constitutes a new and efficient route to compound 2 in an overall yield of 43%.

The crystal structure, thermal behaviour, mass spectrum and protonation of 4-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole (medetomidine) hydrochloride have been investigated. The title compound crystallizes in both hydrated and anhydrous forms, and their structures have been determined by three-dimensional X-ray structure analysis. The crystals of the anhydrous form are monoclinic and those of the hydrated form (containing one hydrate water molecule) are triclinic with unit-cell dimensions: a = 23.861(9), b = 7.721(4), c = 22.037(9) A, beta = 140.20(4) degrees, Z = 8, and space group C2/c, and a = 7.841(4), b = 8.380(3), c = 12.743(6) A, alpha = 93.66(3), beta = 102.90(3), gamma = 116.85(3) degrees, Z = 2, and space group P1, respectively. Thermal decomposition of the title compound has been interpreted from the TG, DTG and DSC curves with the help of mass spectrometry. Medetomidine hydrochloride monohydrate decomposes in four stages. The first is dehydration at 45-100 degrees C, the second is evaporation of HCl and medetomidine base at 200-320 degrees C, and the third and fourth are decomposition at 340-570 degrees C. The protonation constant is 7.04 in aqueous 0.1 M NaClO4 (25 degrees C).

Nineteen different carotenoids have been isolated from various harvests of Mytilus edulis (edible mussels). Besides beta,beta-carotene (occasional) these were ten acetylenic C40-carotenoids: crocoxanthin-like, anhydro-amarouciaxanthin B, 19'-hexanoyloxyisomytiloxanthin, isomytiloxanthin, alloxanthin, mytiloxanthin, amarouciaxanthin B-like, halocynthiaxanthin, pectenol-like and heteroxanthin; two acetylenic C37-carotenoids: pyrrhoxanthinol and hydrato-pyrrhoxanthinol; four C40-skeletal allenic carotenoids: 19'-hexanoyloxyfucoxanthin, fucoxanthin, 19'-hexanoyloxyfucoxanthinol and fucoxanthinol; two C37-skeletal allenic carotenoids: peridinin and peridininol. Anhydro-amarouciaxanthin B, 19'-hexanoyloxyisomytiloxanthin (minor occasional) and hydrato-pyrrhoxanthinol constitute new carotenoids. The characterization comprised TLC and HPLC behaviour, VIS spectrophotometry, 1H NMR (including full assignment of three new carotenoid end groups), CD and mass spectra, as well as chemical derivatizations. Stereochemical considerations are discussed.

An immunological epitope has been located at the well preserved heptade discontinuity in Coil 2B of human cytokeratin 8, with the aid of synthetic peptides, antibodies to these and monoclonal antibodies to cytokeratins. CD revealed 37% alpha-helix in a 31-peptide.

The packing of DNA is described using the formalism of differential geometry. Winding of the DNA double helix around the histone 2-5 octamer forming a nucleosome and the condensation of the so-formed bead-on-a-string chromatine aided by histone 1 is interpreted as two consecutive isometric, i.e. Bonnet, transformations. The DNA double helix can be approximated to a helicoid which can be transformed isometrically to a catenoid, an approximation of the nucleosome. Owing to the organization of the histone octamer the extended chromatine takes a helicoidal shape allowing a second Bonnet transformation to consummate the condensation into a chromatine fibre.

The major degradation product of desonide in a pharmaceutical ointment formulation has been shown to be identical with the C-17-carboxylic acid obtained on oxidative cleavage of the alpha-ketol group of desonide with alkaline hydrogen peroxide. The pKa value of this acid has been estimated from chromatographic data.