On the correlation between the magnetic structure and the electrical properties of EuB6

Single crystals of EuB₆ were prepared by the floating-zone method. Magnetic and electric measurements on these crystals in the temperature range 1.6–300 K revealed that the pure EuB₆ is an antiferromagnet with a Néel temperature of 5–6 K and has a carrier concentration of 4.2 × 10²⁰ cm^-3. It was found that in polycrystalline sample, defects of Eu ions reduce the carrier concentration and make the sample ferromagnetic. It is suggested that the conduction electrons in pure EuB₆ originate from the overlap of the 4f band tail and the conduction band.     

Further studies on palytoxin. II. structure of palytoxin

The full structure of palytoxin, a potent coelenterate toxin, is reported.     

Structures of xestospongin A,B,C and D,novel vasodilativecompounds from marine sponge, xestospongiaexigua

Xestospongin A,B,C and D represent a new class of macrocyclic 1-oxaquinolizidines, have been isolated from Australian sponge $\text{Xestospongia}$$\text{exigua}$. The structure of xestospongin C has been determined by X-ray analysis.     

Three-dimensional athermal waveguide at 1.3 μm wavelength for temperature independent lightwave devices

To eliminate the temperature dependence of narrow-band filter, a three-dimensional athermal waveguide of which optical path length is independent of temperature was developed at 1.3 μm wavelength. The temperature coefficient of the refractive index of films made of glass materials was measured at this wavelength, and a strip-loaded athermal waveguide was designed using a scalar finite element method. The temperature coefficient of optical path length was successfully decreased to 9.65X10^-9[/K] (0.1% of the conventional waveguide).     

Synthesis and reaction of a new type of 5-deazaflavin with axial and planar chirality

A new type of 5-deazaflavin derivative with axial and planar chirality was synthesized as a flavoenzyme model. A novel optical resolution gave an enantiomeric pair of the 5-deazaflavins 1a,b. Compounds1a,b were optically stable and effectively discriminated PNPH enantiomers in a model reaction of intercoenzyme hydrogen transfer.     

Synthesis of N-methyl and N-11C-methyl spiperone by phase transfer catalysis in anhydrous solvent

Spiperone, a butyrophenone neuroleptic drug, has been used in binding studies of dopamine receptors. L?ngstr?m et al. developed N-11C-methyl spiperone, and, in cooperate with Wagner et al., made it possible to visualize the distribution of dopamine receptors in the human brain in vivo. In this paper, we independently developed another synthetic method of N-11C-methyl spiperone using the phase transfer catalyst in an anhydrous solvent. Separation of the product is feasible only by passing the reactant solution through a Millipore filter and injecting it onto high pressure liquid chromatography (HPLC). The time required for the synthesis and purification of N-11C-methyl spiperone from 11C-methyl iodide and spiperone was 20 min. Radiochemical yield exceeded 35% against 11C-methyl iodide without correcting decay of the radioactivity.     

ESR studies of polyacenic semiconductive material

ESR measurements have been performed on the polyacenic material prepared by the pyrolytic treatment of phenol-formaldehyde resin. Six kinds of samples (A)-(F) with various electrical conductivity (σ) were employed for the measurements. Each sample shows a single narrow line, the g-values of which suggest the existence of unpaired electrons of π-type. If the sample (F) (σ = 1 × 10° S cm^?1) the single narrow line becomes drastically diminished in the presence of a small amount of oxygen.     

Chromatographic resolution of dipeptide enantiomers and diastereomers on chiral stationary phases from poly(L-leucine) or poly(L-phenylalanine)

Two types of chiral stationary phase, polymer-bonded and non-bonded, containing poly(L-leucine) and poly(L-phenylalanine) were prepared. These stationary phases gave higher enantioselectivity for the optical resolution of various derivatives of leucylphenylalanine methyl ester by liquid chromatography than did poly(L-alanine) and poly(L-glutamate).