Beta-delayed γ-ray studies of πf7/2 - νpf shell nuclei

We have utilized the selective process of β decay to populate low-energy excited states in the neutron-rich ₂₂Ti, ₂₃V, ₂₄Cr, and ₂₅Mn nuclei. The goal was to systematically track the monopole shift of the νf_5/2 single-particle level with increased occupancy of the πf_7/2 orbital. The β-decay properties of the parent nuclides, along with the low-energy structure of the daughters, are presented and compared with the results of shell model calculations employing the GXPF1 interaction.     

A new minor butenolide from <Emphasis Type="Italic">Machilus odoratissima</Emphasis>

A new butenolide, designated odoratinolide (1), was isolated from the bark of the Vietnamese medicinal plant Machilus odoratissima. Its structure was determined by spectroscopic analyses.     

NIR spectroscopic study of the dissolution process in pharmaceutical tablets

In this study, water penetration and the interaction between water and a pharmaceutical excipient in a tablet were investigated using near-infrared (NIR) spectroscopy and perturbation-correlation moving-window two-dimensional correlation spectroscopy (PCMW-2DCS). The penetration rate of water into a tablet was mainly dependent on the porosity of the tablet and was less dependent on the type of excipient. This behavior was well described by the Lucas–Washburn theory. The PCMW-2DCS technique revealed that there are two-staged interaction changes in NIR spectra of the water–powder interactions. The first and second changes corresponded to the water–solid interaction and the dissolution of the solid, respectively. The diffusion-controlled dissolution model by Nernst well explained these results.     

Application of sweeping to micellar electrokinetic chromatography-atmospheric pressure chemical ionization-mass spectrometric analysis of environmental pollutants.

An application study of sweeping, an on-line sample concentration technique, to micellar electrokinetic chromatography (MEKC) directly combined with mass spectrometry (MS) using an atmospheric pressure chemical ionization (APCI) interface, namely MEKC-APCI-MS, was investigated to enhance the concentration sensitivity for the analysis of environmental pollutants. Under a neutral condition, around 100-fold increase in the concentration sensitivity was achieved for several aromatic amines and alkyl phthalates as test samples by sweeping-MEKC-APCI-MS compared to conventional MEKC-APCI-MS, whereas under an acidic condition, 100 to 600-fold sensitivity enhancement was gained for similar solutes. Linearity of the corrected peak area obtained in the mass chromatogram against the sample concentration was examined for 3,4-dichloroaniline and diisopropyl phthalate (DIPP). The estimated limits of detection for 3,4-dichloroaniline and DIPP were 0.6 and 0.4 ppm, respectively, in terms of the injected sample concentration.     

Use of potassium-form cation-exchange resin as a conductimetric enhancer in ion-exclusion chromatography of aliphatic carboxylic acids

In this study, a cation-exchange resin (CEX) of the K⁺-form, i.e., an enhancer resin, is used as a postcolumn conductimetric enhancer in the ion-exclusion chromatography of aliphatic carboxylic acids. The enhancer resin is filled in the switching valve of an ion chromatograph; this valve is usually used as a suppressor valve in ion-exchange chromatography. An aliphatic carboxylic acid (e.g., CH₃COOH) separated by a weakly acidic CEX column of the H⁺-form converts into that of the K⁺-form (e.g., CH₃COOK) by passing through the enhancer resin. In contrast, the background conductivity decreases because a strong acid (e.g., HNO₃) with a higher conductimetric response in an eluent converts into a salt (e.g., KNO₃) with a lower conductimetric response. Since the pH of the eluent containing the resin enhancer increases from 3.27 to 5.85, the enhancer accelerates the dissociations of analyte acids. Consequently, peak heights and peak areas of aliphatic carboxylic acids (e.g., acetic acid, propionic acid, butyric acid, and valeric acid) with the enhancer resin are 6.3-8.0 times higher and 7.2-9.2 times larger, respectively, than those without the enhancer resin. Calibrations of peak areas for injected analytes are linear in the concentration range of 0.01-1.0 mM. The detection limits (signal-to-noise ratio = 3) range from 0.10 μM to 0.39 μM in this system, as opposed to those in the range of 0.24-7.1 μM in the separation column alone. The developed system is successfully applied to the determination of aliphatic carboxylic acids in a chicken droppings sample.     

Syntheses of N-aryl-protected glucosamines and their stereoselectivity in chemical glycosylations

N-Aryl-protecting groups were introduced in glucosamines to achieve β-selective glycosylation. Various N-aryl aminosugars were synthesized via Buchwald–Hartwig reaction. Glycosylation using glycosyl trichloroacetimidates of N-aryl aminosugars smoothly proceeded in the presence of trimethylsilyl trifluoromethanesulfonate. Use of a glycosyl donor comprising an electron-donating 2,4-dimethoxyphenyl (DMP) group led to the glycosylation proceeding with high β selectivity. This stereoselectivity seemed to be derived from the formation of an aziridine intermediate. The DMP-protecting group can be removed immediately by using ammonium hexanitratocerate (IV).     

Trifluoroacetaldehyde: A useful industrial bulk material for the synthesis of trifluoromethylated amino compounds

The synthesis of various trifluoromethylated amino compounds was studied using trifluoroacetaldehyde, an industrial bulk material, as a starting compound. One general application of trifluoroacetaldehyde is the preparation of trifluoroethylamino derivatives via reductive amination reaction. This synthesis includes the formation of the corresponding N,O-acetal intermediates followed by their reduction using NaBH₄ or 2-picoline borane complex, affording the target trifluoroethylamino compounds in moderate to good yields (47-87%).Another general application of trifluoroacetaldehyde is the synthesis of chiral α-substituted trifluoroethylamino compounds. In this synthesis, trifluoroacetaldehyde was first converted into the chiral trifluoromethyl tert-butyl sulfinimine, which was subjected to 1,2-nucleophilic addition reactions across its CN double bond. The addition of phenyllithium afforded α-(phenyl)trifluoroethylamino derivative in 83% yield and with 96% de. Allylation and Reformatsky reactions produced the corresponding α-substituted trifluoroethylamino derivatives in 82 and 58% yields and with 90 and 91% de, respectively.