Efficient photochemical oxetane formation from 1-methyl-2,4,5-triphenylimidazole and benzophenones

In contrast to simple imidazoles, 1-methy1–2,4,5-triphenylimidazole ($\text{1}$) produced stable oxetane photoadducts $\text{3b}$ - $\text{e}$ with good efficiency upon irradiation in the presence of benzophenone derivatives $\text{2b}$ - $\text{e}$ in acetonitrile solution. Irradiation in the solid-phase was also studied. The oxetanes $\text{3b}$ - $\text{e}$ readily underwent cycloreversion by acid catalysis or by heating.     

Vibrational spectra and molecular conformations of 1,5-dichloro- and 1,5-dibromopentanes and 1,6-dichloro-and 1,6-dibromohexanes

The Raman and IR spectra of 1,5-dichloro- and 1,5-dibromopentanes and 1,6-dichloro-and 1,6-dibromohexanes have been measured. The normal coordinates have been calculated for these molecules using a consistent set of force constants and the molecular conformations studied by analysing the spectra with reference to the results of the calculations. In the crystalline solid state, 1,5-dichloropentane assumes the trans-trans-trans-gauche form and 1,5-dibromopentane, 1,6-dichloro- and 1,6-dibromohexanes assume the all-trans form. The normal coordinate treatment with the well-established force field was of great help in determining the whole molecular form of the relatively large chain molecules.     

Removal of fine powders from film surface. I. Effect of electrostatic force on the removal efficiency

A novel fine particle removal system composed of a corona-discharge neutralizer, a pulse-jet air unit and an image processing system has been developed. First of all, adhesion force between particle and film was directly measured and effect of electrostatic force on the adhesion force was calculated experimentally and theoretically. The electrostatic force was found to be significant, leading to the suggestion that the countermeasure for the electrostatic force was required to effectively remove fine particles. This system was then applied to the removal of fine particles from surface of a gelatin film used for conventional capsule material. The number of particles removed by the system was calculated by an image processing system and number base removal efficiency was computed with and without the elimination of electrostatic charge by the neutralizer. It was found that the difference between the removal efficiency of particles with elimination of electrostatic charge and that of without the elimination showed linear relationship with the electrostatic adhesion force. The data confirmed the necessity of electrostatic charge elimination for the effective removal of fine particles.     

Facile construction and divergent transformation of polycyclic isoxazoles: direct access to polyketide architectures

[reaction: see text] Base-promoted cyclocondensation of C-chloro oximes with cyclic 1,3-diketones affords functionalized isoxazoles in good yield and under convenient reaction conditions. This process enables the synthesis of highly substituted products with notable functional group tolerance. The products obtained are directly converted to a variety of polyketide-derived polycyclic structures including xanthenes, anthracenes, and benzophenones.     

SPECIFIC PHOTOCOUPLING OF 5-BROMOURIDINE TO TRYPTOPHAN IN AQUEOUS FROZEN SOLUTION§

Abstract —5-Bromouridine (BrUd) photochemically reacted with l -tryptophan (trp) only in aqueous frozen solution giving rise to 2-[1,2,3,4-tetrahydro-1-(β-d -ribofuranosyl)-2,4-dioxo-5-pyrimidinyl]-l -tryptophan ( 1a ). Under similar conditions irradiation of 5-bromouracil (BrU) and trp gave the corresponding coupled product 2. Addition of acetone, potassium carbonate or sodium chloride to the frozen system completely inhibited the photocoupling reaction. These photocoupling reactions are suggested to proceed via mixed aggregate formation between trp and BrUd (or BrU) in frozen aqueous solution. Stacking interactions in these aggregates are characterized by an efficient quenching of trp fluorescence by BrUd. Under the same conditions other amino acids such as phenylalanine, tyrosine, histidine and lysine did not react with BrUd, indicating that the photocoupling of BrUd (or BrU) is specific for trp.     

Amidase and peptidase activities of polyclonal immunoglobulin G present in the sera of patients with rheumatoid arthritis

Polyclonal Immunoglobulin (Ig) G from patients with rheumatoid arthritis (RA) and healthy subjects hydrolyzed carbobenzoxy−Val−Gly−Arg p-nitroanilide and D−Pro−Phe−Arg p-nitroanilide. RA IgG exhibited higher activity against the former substrate, but not the latter. On the other hand, RA IgG showed reduced activity against D−Pro−Phe−Arg methylcoumarinamide, when compared with those of the healthy controls. These results suggest that RA IgGs differ from normal IgGs in the substrate specificity of amidase activity. Preliminary studies have shown that two out of three RA IgG samples cleaved a pentapeptide—Gln−Arg−Arg−Arg−Ala−Ala— which is assumed to be associated with the risk of developing RA (Gregersen, P. K. et al. (1987), Arthritis Rheum. 30, 1205–1213). By contrast, virtually no cleavage of the same peptide was observed with IgG from healthy controls. A peptide analog, Gln−Arg−Arg−Trp−Ala, was not cleaved at all by any IgGs examined either from RA patients or healthy controls.     

Mechanism of selective p-quinol formation in the cobalt schiff base complex-catalyzed oxygenation of 4-alkyl-2,6-di-t-butylphenols

The selective formation of $\text{p}$-quinols in the Co(Salpr)-catalyzed oxygenation of 4-alkyl-2,6-di-$\text{t}$-butylphenols in MeOH has been found to involve the rate determining reduction of peroxy-$\text{p}$-quinolato Co(III) complex formed in the initial fast step. An ionic mechanism of the reduction of the OO bond in the peroxy complex by MeOH has been discussed based on kinetic studies. The reactive species in the catalytic cycle is found to be [Co(III)(Salpr)(OH)].     

Improving the properties of the proton exchange membranes by introducing α-methylstyrene in the pre-irradiation induced graft polymerization

New proton exchange membranes (PEMs) were prepared by pre-irradiation induced grafting of α-methylstyrene (AMS)/styrene (STY)/divinylbenzene (DVB) into the crosslinked polytetrafluoroethylene (RX-PTFE) films and successively sulfonated. The new PEMs showed the improved glass transition temperature and chemical stability as compared with the PEMs prepared by pre-irradiation induced grafting of STY/DVB. The balance of the cost, grafting kinetic, thermal properties and the properties of the resulted proton exchange membrane is the key point of this work.     

A new route to 3-alkyl-2,5-di-t-butyl-2,4-cyclopentadienones from 4-alkyl-2,6-di-t-butylphenols

Base-catalyzed reaction of 5-acylmethyl-2,5-di-$\text{t}$-butyl-4-oxa-2-cyclopentenones selectively derived from 4-alkyl-2,6-di-$\text{t}$-butylphenols $\text{via}$ three steps involving oxygenation, acetylation, and acid-treatment gave 3-alkyl-2,5-di-$\text{t}$-butyl-2,4-cyclopentadienones in excellent yield.     

Isolation of new quinidine metabolites and simultaneous determination of quinidine and its metabolites in blood and urine by direct injection HPLC analysis

Summary New quinidine metabolites, including 10,11-dihydrodiol quinidine N-oxide, 10,11-dihydrodiol quinidine and their glucuronides, were found in human urine. A quinidine monitoring HPLC method including these metabolites, is proposed by the direct injection of body fluid samples onto the precolumn for deproteinization followed by reverse phase separation in the analytical column with a column switching technique. The recovery of spiked quinidine and its metabolites in plasma was quantitative (98–102%) with good reproducibility (C.V.: 1.6–4.0%). Several clinical samples such as whole blood and urine were analyzed by the present method.