Kazue Ohkura

A simplified and improved synthesis of [11C]phosgene with iron and iron (III) oxide.

[11C]Phosgene ([11C]COCl2), a useful precursor for labeling several radiopharmaceuticals, is generally produced by catalytic oxidation of [11C]carbon tetrachloride over Fe granules, although in low yields or with poor reproducibility. In order to develop am improved synthesis of [11C]phosgene, two oxidizing agents, Fe2O3 and CuO, were examined. The yield of [11C]phosgene was significantly increased using Fe2O3 powder mixed with Fe granules, while the use of CuO alone, or CuO powder mixed with Fe granules resulted in an insignificant yield. The yield and specific activity of S- (-) [11C]CGP-12177 synthesized using Fe2O3 powder mixed with Fe granules were markedly higher than those synthesized by the previous methods using Fe granules alone or Fe granules mixed with Fe powder. Thus, in the present study, we developed a simple and practical method for the synthesis of [11C]phosgene, which provided an improved yield of S- (-) [11C]CGP-12177.

Separation and Identification of Taxifolin 3- O -Glucoside Isomers from Chamaecyparis Obtusa (Cupressaceae)

Taxifolin 3- O -glucoside isomers, [(2R, 3R)-, (2R, 3S)-, (2S, 3R)- and (2S, 3S)-] were isolated from leaves of Chamaecyparis obtuse (Cupressaceae). Their structures were elucidated on the basis of UV, MS, CD, 1 H- and 13 C-NMR spectral data, including 2D shift correlation. It was found that the compounds could be distinguished by the use of 1 H- and 13 C-NMR spectral data.

Stereoselective synthesis of 4a-fluoro-5,10-ethenobenzo[f]quinazolines via photo-Diels–Alder reaction of 5-fluoro-1,3-dimethyluracil with naphthalenes

UV-irradiation of a solution of 5-fluoro-1,3-dimethyluracil (5-FDMU) in aprotic media effected a stereoselective 1,4-cycloaddition reaction to give a barrelene derivative in high yield. In direct contrast, irradiation of a solution of 5-FDMU and naphthalene in a protic medium afforded 5-(1-naphthyl)uracil as the major product.

Increased [18F]2-fluoro-2-deoxy-d-glucose ([18F]FDG) yield with recycled target [18O]water: factors affecting the [18F]FDG yield

The reuse of [18O] water after being purified by distillation has been reported to give lower [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) yields, probably due to the presence of organic impurities. In our routine production of [18F]FDG, however, we observed increased [18F]FDG yields with recycled [18O]water. Thus, factors affecting [18F]FDG yield were examined using as-purchased (virgin) and recycled (by photochemical combustion and distillation) [18O]water. [18F]FDG was synthesized by nucleophilic 18F-fluorination on a quaternary 4-aminopyridinium resin. The recycled [18O]water gave an [18F]FDG yield significantly higher than did the virgin water, without any significant difference in the [18F]fluoride yield. Levels of several ionic impurities including Cl- and Ca2+ were significantly higher in the virgin [18O]water than in the recycled water, while significantly larger amounts of organic impurities were detected in the former. Hence, trace amounts of organic impurities were not responsible for the lower [18F]FDG yield. Chloride anion in the [18O]water may compete with [18F]fluoride to lower the [18F]FDG yield.

The pyridyl cation as a reactive intermediate in the photoreaction of iodopyridines with benzenes

Abstract The electrophilic behavior of the reactive entity in the phtosubstitution of benzenes with 2-iodopyridine was found to be ascribable to the intermediary 2-pyridyl cation, rather than to the electrophilic 2-pyridyl radical.

Acid-catalyzed phororeaction of 6-chloro-1,3-dimethyluracil in benzene ; synthesis of cyclooctapyrimidine-2,4-dione

The photolysis of 6-chloro-1,3-dimethyluracil in benzene afforded 1,3-dimethyl-6-phenyluracil, while the photoreaction in the presence of trifluoroacetic acid afforded 1,3-dimethylcyclooctapyrimidine-2,4-dione as a major product

A facile synthesis of N-(2- and 4-pyridyl) indoles

The reactions of the sodium salts of indoles with 2- and 4-fluoropy- ridines afforded the corresponding N-pyridylindoles in good yields, whereas the reaction with 3-fluoropyridine gave no coupling product

Photochemical Synthesis of Naphtho- cyclobutapyrimidines via 1,2-Cyclo- addition of 6-Chloro-1,3-dimethyluracil with Naphthalenes

UV-Irradiation of a solution of 6-chloro-1,3-dimethyluracil (6-CIDMU) and naphthalene in a non-polar solvent (cyclohexane) afforded 6-(1-naphthyluracil) as the sole product. In contrast, irradiation of a solution of 6-CIDMU and naphthalene in a polar medium in the absence of TFA effected 1,2-cycloaddition to give naphthocyclobutapyrimidines in moderate yields. This photocycloaddition reaction also proceeds in non-polar solvents in the presence of TFA.

Synthesis and Antiviral Activity of Novel Fluorinated 2′,3′‐Dideoxynucleosides

A series of 5‐(trifluoroethoxymethyl)‐2′,3′‐dideoxyuridines and 5‐[bis(trifluoroethoxy)‐methyl]‐2′,3′‐dideoxyuridines have been prepared and screened for antiviral activity. The conformations of these compounds are discussed on the bases of NOE studies and the MO calculations. Modelling and NOE studies suggest both syn‐ and anti conformations for these 5‐(2,2,2‐trifluoroethoxymethyl)‐ and 5‐[bis(2,2,2‐trifluoroethoxy)‐methyl]‐ derivatives. The NOE parameters are also suggested to be more attributable to the nature of the fluorine atom than to structural or conformational changes. Compounds 17, 26 and 30 showed some activity in anti‐HIV‐1 and anti‐HIV‐2 assays, but the compounds were devoid of activity against HSV and human rhinovirus. The compounds tested exhibited low cytotoxicity and were inactive against a bank of cancer cells in vitro. †In honor and celebration of the 70th birthday of Professor Leroy B. Townsend.

Mode Switching during the Cycloaddition of 5-Fluoro-1,3-dimethyluracil with Naphthalene from 1,4- to 1,2-Addition

UV-irradiation of a solution of 5-fluoro-1,3-dimethyluracil (5-FDMU) and naphthalene (1) in acetonitrile effected both 1,2- and 1,4-cycloaddition. The 1,2-cycloaddition proceeds more smoothly than the alternative 1,4-cycloaddition. The 1,2-cycloadduct (2), however, is labile to the UV-light used for the reaction, and is rapidly converted to 5-FDMU and naphthalene, while the 1,4-adduct (3) is insensitive to UV-light. Thus, 2 is obtained as the major product by short-period irradiation, while 3 is produced predominantly when the irradiation duration is prolonged. Mode-selective 1,2-cycloaddition is achieved when UV-irradiation is performed in the presence of piperylene.