Diastereoselective hydroformylation of 2,5-cyclohexadienyl-1-carbinols with catalytic amounts of a reversibly bound directing group

A phosphinite plays a role as a reversibly bound directing group for the regio- and diastereoselective hydroformylation of 2,5-cyclohexadienyl-1-carbinols. Of the two alkene functions only one was functionalized through hydroformylation to form a synthetically attractive quaternary carbon center leaving the second alkene function for potential further functionalization.     

Kinetic study of proton-transfer reactions of phenylnitromethanes. Implication for the origin of nitroalkane anomaly

Measurements of rate constants and substituent effects for three important elementary steps of proton-transfer reactions of phenylnitromethane were reported. The Hammett ρ values for the deprotonation of ArCH(2)NO(2) with OH(-), protonation of ArCH═NO(2)(-) with H(2)O, and protonation of ArCH═NO(2)(-) with HCl were determined in aqueous MeOH at 25 °C. Comparison of these experimentally observed ρ values with those calculated at B3LYP/6-31G* revealed that aci-nitro species (ArCH═NO(2)H), which is formed on the O-protonation of ArCH═NO(2)(-), does not lie on the main route of the proton-transfer reaction. Analysis of the Br?nsted plot implies that the proton-transfer reaction of most XC(6)H(4)CH(2)NO(2) exhibits nitroalkane anomaly, but not for p-NO(2)C(6)H(4)CH(2)NO(2), and that the transition state charge imbalance is an origin of anomaly.     

Determination of environmental actinide nuclides and210Pb(210Po) by low-energy photon spectrometry with alpha-spectrometry

Low-energy photon spectrometry with -spectrometry was used to determine the environmental concentrations of low-level actinides and other nuclides, especially²¹⁰Pb and²¹⁰Po. The isotopic ratio of²⁴⁰Pu/²³⁹Pu was successfully determined by measuring L_x-ray/-ray counting ratio. A reliable method has been developed for the determination of extremely low-level²³⁷Np global fallout in environmental samples. The non-destructive determination by Ge-LEPS for natural²¹⁰Pb in various samples (tobacco leaves, commercially available tobacco, etc.) was also carried out with the determination of²¹⁰Po by -spectrometry using²⁰⁹Po as a yield tracer.     

Cationic polymerization of formaldehyde in liquid carbon dioxide. Part II: A kinetic study of the polymerization

The kinetic behavior on the polymerization of formaldehyde with and without acidic catalyst, in liquid carbon dioxide, in the temperature range of 30 to 50°C. was investigated. In the polymerization without catalyst both the polymer yield and the degree of polymerization increased with reaction time and also with rising temperature. With acidic catalyst, such as acetic acid and dichloroacetic acid, both the polymer yield and the degree of polymerization increased more than that in the polymerization without catalyst. The overall rate of polymerization with and without acidic catalyst was expressed by the first-order rate equation with respect to monomer concentration. From the results it was concluded that the polymerizations belonged to a type of successive polymerization with rapid initiation and no termination. The rate constant and the activation energy of each elementary process of polymerization were estimated on the basis of the results.     

Concise total synthesis of (-)-spongotine A

The first asymmetric total synthesis of spongotine A is described. The oxidative synthesis of the imidazoline/ketone unit from keto aldehyde and diamine is a key step in this synthesis. The absolute stereochemistry of the asymmetric center of natural spongotine A is revealed as the (S)-configuration.     

Formation of Supramolecular Nanostructures through in Situ Self-Assembly and Post-Assembly Modification of a Biocatalytically Constructed Dipeptide Hydrazide**

Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.     

Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides in phosphate rocks and phosphate fertilizers

Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides have been studied for 2 phosphate rocks and 7 phosphate fertilizers. Uranium contents were found to be rather high (39-117 ppm) except for phosphate rock from Kola. The uranium series nuclides were found to be in various equilibration states, which can be grouped into following three categories. Almost in the equilibrium state, 238U approximately 230Th greater than 210Pb greater than 226Ra and 238U greater than 230Th greater than 210Pb greater than 226Ra. Thorium contents were found to be, in general, low and appreciable disequilibrium of the thorium series nuclides was not observed except one sample. Potassium contents were also very low (less than 0.3% K2O) except for complex fertilizers. Based on the present data, discussions were made for the radiation exposure due to phosphate fertilizers.