Enantioselective total synthesis of heliespirone B

The first enantiocontrolled total synthesis of heliespirone B has been accomplished employing a biomimetic intramolecular oxy-Michael reaction followed by the regio- and diastereoselective reduction of the carbonyl function as key steps.     

Regioselectivity in the acylation of methylhydroquinone dimethyl ether: an unprecedented case of indirect steric hindrance

The origin of the highly regioselective acylation of methylhydroquinone dimethyl ether was investigated using geometry minimization (ab initio and DFT) and NOE spectroscopic measurements. The theoretical and experimental results were consistent with the indirect participation of the aromatic methyl group in blocking the electrophile attack at position 3 of the aromatic ring.     

K-birnessite MnO2: a new selective oxidant for benzylic and allylic alcohols

K-birnessite, which is readily prepared by the pyrolysis of KMnO₄, acts as a convenient new oxidant for benzylic and allylic alcohols.     

Aluminum alkoxide complexes from highly substituted 3,4‐epoxy alcohols: An NMR and computational study

The organoaluminum mediated epoxide ring opening of epoxy alcohols is a key step in the oxirane‐based approach for polypropionate synthesis. However, this reaction has shown unanticipated regioselectivities when applied to 2‐methyl‐3,4‐epoxy alcohols. In order to gain mechanistic insight into the factors controlling the epoxide ring opening process, diastereomeric 2‐methyl‐3,4‐epoxy alcohols were reacted with triethylaluminum in order to identify the aluminum complexes formed by these systems. Different epoxide–aluminum complexes were calculated using ab initio HF/[13s7p/11s5p] and B3PW91/6‐31G** gauge‐including atomic orbital (GIAO) methods and compared to the experimental NMR data. The calculated and experimental data correlates with the aluminum dimer complex (TIPSOCH₂CH(OAlEt₂)CH(CH)₃CHCH(O)(AlEt₃))₂ (VIII) for the systems favoring the nucleophilic attack at the external C4 epoxide carbon, while an unusual trialuminum species TIPSOCH₂CH(OAlEt₂)CH(CH)₃CHCH(O)(AlEt₃)₂ (X) is consistent with the systems favoring the internal C3 attack. The ²⁷Al NMR data established the tetracoordinated nature of the aluminum metal in all alkoxy aluminum intermediates, while the ¹³C NMR data provided insight into the aluminum‐oxygen coordination. The formation of the complexes was dictated by the stereochemical disposition of the substituents. These complexes are different from the generally accepted bidentate intermediates proposed for 2,3‐epoxy alcohols and simpler 3,4‐epoxy alcohols. Copyright © 2012 John Wiley & Sons, Ltd.     

Performance test of passive radon–thoron discriminative detectors on environmental parameters

This paper describes how humidity, wind and ambient aerosols in air influence the detection responses of passive detectors. Two types of alpha track detectors based on a passive radon (²²²Rn)–thoron (²²⁰Rn) discriminative measurement technique were used: the Raduet and Radopot detectors that were developed and calibrated by the National Institute of Radiological Sciences, Japan. The initial experiment showed that the infiltration rate of ²²⁰Rn onto sponges with a high air exchange rate for the Raduet detectors was one third lower than that onto filters for the Radopot detectors. Little distinct dependence on humidity was observed for the ²²²Rn detection responses of both detectors. For ²²⁰Rn, the detection responses of both detectors for the high air exchange rate seemed to decrease slightly at high humidity conditions. The ²²⁰Rn detection responses of the Radopot detectors had little influence from wind speed. The ²²⁰Rn detection responses of the Raduet detectors for the high air exchange rate seemed to decrease at low wind speeds. Furthermore, there was little difference between the detection responses in the presence and absence of ambient aerosol particles because the ambient aerosols were filtered out during their passive diffusion through the sponges and filters for the Raduet and Radopot detectors, respectively.     

The emergence of different tail exponents in the distributions of firm size variables

We discuss a mechanism through which inversion symmetry (i.e., invariance of a joint probability density function under the exchange of variables) and Gibrat’s law generate power-law distributions with different tail exponents. Using a dataset of firm size variables, that is, tangible fixed assets K$K$, the number of workers L$L$, and sales Y$Y$, we confirm that these variables have power-law tails with different exponents, and that inversion symmetry and Gibrat’s law hold. Based on these findings, we argue that there exists a plane in the three dimensional space (logK,logL,logY)$(logK,logL,logY)$, with respect to which the joint probability density function for the three variables is invariant under the exchange of variables. We provide empirical evidence suggesting that this plane fits the data well, and argue that the plane can be interpreted as the Cobb–Douglas production function, which has been extensively used in various areas of economics since it was first introduced almost a century ago.     

Analyzing Power in Elastic Scattering of Polarized Protons from Neutron-rich Helium Isotopes

The vector analyzing power has been measured for the elastic scattering of neutron-rich ⁶He from polarized protons at 71 MeV/nucleon. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a ⁶He nucleus. An optical model analysis revealed that the spin-orbit potential for ⁶He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semi-microscopic analysis with a α + n + n cluster folding model suggests that the inclusion of realistic interaction between a proton and the α core is important in describing the p-⁶He elastic scattering.     

π 0 and η Photoproduction on the Deuteron at ELPH, Tohoku University

Baryon spectroscopy is important to understand Quantum Chromodynamics at low energies. In this purpose, a series of π ⁰ and η photoproduction experiments was carried out with an electro-magnetic calorimeter FOREST at Research Center for Electron Photon Science, Tohoku University. The incident tagged bremsstrahlung photon energy ranges from 550 to 1,150 MeV. The differential and total cross sections obtained for π ⁰ and η photoproduction processes on the proton are consistent with the SAID and MAID calculations. The analysis of π ⁰ and η photoproduction on the neutron is underway.     

First-principles study on superconductivity of the gold–indium alloy under high pressure

The superconductivity of gold–indium alloys has been investigated using first-principles calculations based on the density functional theory. At ambient pressure, the calculated superconducting transition temperature (T _c) is 0.04 μ K in pure gold, but T _c dramatically increases by substituting indium atoms for gold atoms. The gold–indium alloy having 12.5 atomic percent indium (Au_0.875In_0.125) shows T _c of 0.1 K, and Au_0.75In_0.25 marks 1.7 K. The dramatic increase in T _c owing to the alloying effect is caused by the enhancement of the electron–phonon coupling. The superconductivity of gold is predicted to be drastically weakened with increasing pressure and virtually disappear at 10 GPa, but it continues up to at least 30 GPa by the inclusion of indium atoms.