Stereoselective synthesis of CF3-substituted aziridines by Lewis acid-mediated aziridination of aldimines with diazoacetates

Treatment of trifluoroacetaldehyde N,O-acetal with diazoacetate in the presence of a Lewis acid furnished CF₃-substituted aziridinecarboxylates in good yields. Both cis and trans isomers were obtained stereoselectively by the proper choice of the ester substituents. Use of a chiral diazoacetate derived from (R)-pantolactone led to highly diastereoselective aziridination (94% de).     

Synthesis and properties of polydiene and polypentenamer having formyl or hydroxymethyl groups and their photosensitive derivatives

cis-1,4-Polybutadiene and polypentenamer having pendant functional groups such as formyl, aldoxime, hydroxymethyl, or cinnamoyloxymethyl groups have been prepared, and some of their properties were investigated in terms of structural effect on physical properties of these polymers. cis-1, 4-Polybutadiene and polypentenamer having a different content of formyl group were prepared by the hydroformylation reaction with rhodium catalyst under mild conditions. The pendant formyl group was reduced to a hydroxymethyl group by using various reducing agents such as sodium borohydride or sodium trimethoxyborohydride which were effective to avoid a crosslinking reaction among the formyl groups. Glass transition temperature of polypentenamer having hydroxymethyl groups increased with increasing the content of the hydroxymethyl groups in the polymer. Cinnamoyl group was introduced into the polypentenamer having hydroxymethyl groups by reacting with cinnamoyl chloride so as to prepare a photosensitive rubber. The relationships between the photosensitivity of the cinnamoylated polypentenamer and the mobility of polymer main chains have been elucidated. A linear relationship between the photodimerization rate constant and the difference between ultraviolet (UV) irradiation temperature and the glass transition temperature of the polymer was found. It has become apparent that the photosensitivity of cinnamoylated polypentenamer can be estimated by the glass transition temperature of the original polymer, UV irradiation temperature, activation energy of the dimerization, and γ, which is a coefficient of the relationship between the photosensitive group concentration and the glass transition temperature of the polymer.     

Activity of artificial mutant variants of human growth hormone deficient in a disulfide bond between Cys53 and Cys165

In order to understand the role of Cys53 and Cys165 of human growth hormone (hGH) in receptor-binding and biological activity, artificial mutant variants of hGH were prepared in Escherichia coli by in vitro mutagenesis. Variants of hGH were constructed by replacement of Cys165 with Ala ([Ala165]hGH) or Ser ([Ser165]hGH), by replacement of Cys53 with Ala ([Ala53]hGH), by replacement of Cys53 and Cys165 with Ala ([Ala53, Ala165]hGH), or by replacement of Cys53 with Ala and Cys165 with Ser ([Ala53,Ser165]hGH). All of the variants constructed as well as reduced hGH exhibited less biological activity than that of intact hGH, and the decreases in biological activity were almost equal, as measured by a sensitive biological assay for growth hormone: adipose conversion assay using 3T3-F442A cells. These variants also showed less receptor-binding activity than that of intact hGH. These results suggest that it is possible neither the residue Cys53 nor Cys165 is directly involved in the receptor binding, and that the disulfide bridge between Cys53 and Cys165 in hGH may not always be crucial for the biological activity, though necessary to express full hGH activity.     

Prospective study to assess the clinical efficacy of bone scintigraphy--some analyses of clinical data

The value of preoperative bone scans in patients with primary breast and prostate cancer was evaluated prospectively. Of 414 patients with breast cancer, clinical stage I is 14, II is 219, IIIA is 59, IIIB is 39 and IV is 14. Of 88 patients with prostate cancer, clinical stage I is 14, II is 15, III is 18 and IV is 41. 11 percent of patients with breast cancer and 54 percent of patients with prostate cancer had bone metastases. Clavicle, ribs, thoracic spine, lumbar spine and pelvis metastasized most frequently. The incidences of bone metastases were 18.4% with Scirrhous carcinoma, 15.4% with Medullary tubular carcinoma and 3.8% with Papillotubular carcinoma. The methodology and results of ROC analysis were described in our other papers. Some results of data analysis were described in this paper.     

Silicon hydrides and nickel complexes : III. Hydrosilylation of olefins with dichloro[1,2-bis-(dimethylphosphino)-1,2-dicarba-closo-dodecaborane]-nickel(II) as catalyst

The hydrosilylation of olefins catalyzed by nickel(II) chloride complexed with 1,2-bis(dimethylphosphino)-1,2-dicarba-closo-dodecaborane produces terminal and internal adducts in comparable amounts. This unusual feature of the reaction is explained in terms of the electron-accepting nature of the carboranyl group.     

Time evolution of density fluctuation in the supercritical region. 2. Comparison of hydrogen- and non-hydrogen-bonded fluids

The time evolution of the density fluctuation of molecules is investigated by dynamic light scattering in six neat fluids in supercritical states. This study is the first to compare the dynamics of density inhomogeneity between hydrogen- and non-hydrogen-bonded fluids. Supercritical methanol and ethanol are used as hydrogen-bonded fluids, whereas four non-hydrogen-bonded fluids were used: CHF(3), C(2)H(4), CO(2), and Xe. We measure the time correlation function of the density fluctuation of each fluid at the same reduced temperatures and densities and investigate the relationship between the dynamic and static density inhomogeneities of those supercritical fluids. In all cases, the profile of the time correlation function of the density fluctuation is characterized by a single-exponential function, whose decay is responsible for the dynamics characterized by hydrodynamic conditions. We obtain correlation times from the time correlation function and discuss dynamic and static inhomogeneity using the Kawasaki theory and the Landau-Placzek theory. While the correlation times in the six fluids show noncoincidence, those values agree well with each other except for the supercritical alcohols when scaled to a dimensionless parameter. Although the principle of corresponding state is observed in the non-hydrogen-bonded fluids, both the supercritical methanol and ethanol deviate from that principle. This deviation is attributed to the presence of hydrogen bonding among alcohol molecules at high temperature and low density. The average cluster size of each fluid is estimated under the same thermodynamic conditions, and it is shown that the clusters of supercritical alcohols are on average 1.5-1.7 times larger than those of the four non-hydrogen-bonded fluids. Moreover, the thermal diffusivity of each neat fluid is obtained over wide ranges of density and temperature.     

γ-Radiolysis of 5-fluorouracil and 5-fluorouridine derivatives having sulfur-containing substituents

γ-Radiolysis reactions of eight 5-fluorouracil (5-FU) derivatives having sulfonyl group-containing substituents at the 1-position and five 5-fluorouridine (5-FUR) derivatives having thioureido group-containing substituents were studied under the conditions where hydrated electron (e_aq^?) and hydroxyl radical (HO·) become the principal reactive species. The 5-FU and 5-FUR derivatives were radiolyzed to give 5-FU and 5-FUR, respectively. The efficiency of the reactions depended upon the nature of reactive species and also upon the nature of substituents. The reactivity features of the γ-radiolysis reactions are discussed.     

Reactivity of cobaloxime bound to polystyrene chain by carbon–cobalt σ bond

The (alkyl)-bis(dimethylglyoximato)pyridinecobalt attached to polychloromethylstyrene by a cobalt–carbon bond was prepared by the reaction of Co(II)(DH)₂Py with polychloromethylstyrene in benzene. The fraction of p-vinylbenzyl·Co(DH)₂Py introduced to the polymer was 8.1 and 2.1 mole %. The photodecomposition of the polymer-bonded cobaloxime was investigated by following the change of the visible spectrum. The rate constant k_dec of the polymer-bonded cobaloxime was 1.1 × 10^?2 sec^?1 in benzene; it is one-fourth of that of its monomeric analog, benzyl·Co(DH)₂Py. The k_dec values of the cobaloximes were also measured in benzene–dimethyl sulfoxide mixed solvents, and the polymer effects were discussed. The dependence of the photodecomposition on energy of the irradiation light was investigated, and it was found that the absorption band near 470 nm is important for the photodecomposition of the cobalt–carbon bond. Spectroscopic measurements of the ligand exchange reaction of polymer-bonded cobaloxime with pyridine in dimethyl sulfoxide gave a larger equilibrium constant (1.2 × 10⁴ liter/mole) than that of benzyl·Co(DH)₂Py (9.4 × 10² liter/mole). The kinetic data of the ligand exchange reaction indicated that the larger equilibrium constant for the polymeric system is due to the smaller rate constant of the reverse reaction. The thermodynamic parameters were also obtained.