Particle Sizing by Planar-Phase Doppler System

Conventional phase Doppler systems are useful for sizing particles in the order of microns, but sensitive to the Gaussian beam defect which can cause sizing errors. The defect can be significant when a large size is measured. In this paper, we present a new phase Doppler system using a planar optical layout which permits large particles to be measured in a forward scattering scheme without the Gaussian beam errors. The optical system design is discussed by numerical simulation based on the Mie theory.     

A facile synthesis of 1-aryl-3-heteroaryl-1H-pyrazolo[3,4-b]quinoxalines and related compounds with antifungal activitySynthesis of 1-Aryl-3-heteroaryl-1H-pyrazolo[3,4-b]quinoxalines

The novel 1H-pyrazolo[3,4-b]quinoxalines (flavazoles) 9–15 were synthesized from 3-methoxycarbonylmethylene-2-oxo-1,2,3,4-tetrahydroquinoxaline 6 via a convenient hydrazone synthesis, and these flavazoles were clarified to have the antifungal activity.     

Determination of Binding Constants for Cyclodextrin Complexes with Alkanols by the 1H NMR Measurements of Longitudinal Relaxation Time Using Tetramethylammonium Chloride as an Internal Reference

The longitudinal relaxation times (T₁)of ¹H NMR signals for a variety of alkanols in D₂Omarkedly decreased with increasing concentrations (c)of - and -cyclodextrins (CD). Tetramethylammoniumchloride (TMA) used as an internal reference wasavailable for evaluating an effect of solutionviscosity on relaxation rates R(=1/T₁), since TMAshowed no appreciable interaction with CD. Changes inthe ratio of R for alkanol protons to R for TMAprotons with c were analyzed by the curve-fittingmethod to give K_a. These K_a values agreedwell with those obtained by the analysis of changesin , indicating that T₁ measurement is available forthe determination of K_a for CD complexes. 2D ROESYspectra provided definite information on the molecularstructures of CD complexes with alkanols.     

Photon antibunching from a single quantum-dot-microcavity system in the strong coupling regime

We observe antibunching in the photons emitted from a strongly coupled single quantum dot and pillar microcavity in resonance. When the quantum dot was spectrally detuned from the cavity mode, the cavity emission remained antibunched, and also anticorrelated from the quantum dot emission. Resonant pumping of the selected quantum dot via an excited state enabled these observations by eliminating the background emitters that are usually coupled to the cavity. This device demonstrates an on-demand single-photon source operating in the strong coupling regime, with a Purcell factor of 61+/-7 and quantum efficiency of 97%.     

Mechanistic study on the enantiodifferentiating anti-Markovnikov photoaddition of alcohols to 1,1-diphenyl-1-alkenes in near-critical and supercritical carbon dioxide

Enantiodifferentiating anti-Markovnikov photoaddition of alcohol (methanol, ethanol, 2-propanol, and tert-butanol) to aromatic alkene (1,1-diphenylpropene and 1,1-diphenyl-1-butene), sensitized by optically active alkyl and saccharide naphthalene(di)carboxylates, was investigated in supercritical carbon dioxide at varying pressures to elucidate the effects of clustering on photosensitization and enantiodifferentiation behavior, in particular on the product's enantiomeric excess (ee). For all the alkene/alcohol/chiral sensitizer combinations examined, a sudden change in the product's ee was consistently observed near the critical density, which is attributable to the critical pressure dependence of clustering around the intervening exciplex intermediate.     

Supramolecular chirogenesis in bis-porphyrins: interaction with chiral acids and application for the absolute configuration assignment

[structure: see text] A new supramolecular chirogenic system on the basis of bis(free base porphyrin) and various enantiopure acids, which can be effectively applied for the chirality sensing purposes, is reported. The temperature and solvent are found to be key factors controlling the chirality transfer process in these assemblies.     

New entry to convertible isocyanides for the Ugi reaction and its application to the stereocontrolled formal total synthesis of the proteasome inhibitor omuralide

The development of a new convertible isocyanide, indole-isocyanide, for ready access to pyroglutamic acids culminated in the formal total synthesis of the proteasome inhibitor omuralide featuring a stereocontrolled Ugi reaction. Indole-isocyanide was named after the facilitation of hydrolysis of the resulting 2-(2,2-dimethoxyethyl)anilide via an N-acylindole intermediate obtained by the Ugi multicomponent condensation reaction followed by the indole formation.     

Highly selective oligosaccharide sensing by a Curdlan-polythiophene hybrid

An in situ hybrid complex of Curdlan with water-soluble polythiophene functioned as a highly sensitive and selective saccharide chemosensor in aqueous media, enabling us to discriminate tetrasaccharide acarbose at 1 μM from 24 mono-, di-, tri-, tetra-, and pentasaccharides.     

Enantiodifferentiating photoisomerization of (Z,Z)-1,3-cyclooctadiene included and sensitized by naphthoyl-curdlan

6-O-(2-naphthoyl)curdlan was newly synthesized as a sensitizing polysaccharide host to examine the chiroptical properties, supramolecular complexation, and photochirogenic behavior with (Z,Z)-1,3-cyclooctadiene (1ZZ). The enantiodifferentiating photoisomerization of 1ZZ included and sensitized by this polysaccharide host gave a highly strained chiral (E,Z)-isomer in up to 8.7% enantiomeric excess (ee) in solution and 11.7% ee in the solid state, which are the highest values ever reported for a supramolecular photochirogenesis of 1EZ.     

Doubly activated supramolecular reaction: transesterification of acyclic oligoether esters with metal alkoxides

Transesterification reactions of acyclic oligoether esters E3-E10 with metal alkoxides were accelerated upon noncovalent complexation of the esters with metal ions. In the reaction of monovalent alkaline metal alkoxides, CH(3)ONa and CH(3)OK, plots of the observed rate constants k(obs) with respect to the chain length of E3-E10 showed selective acceleration of the transesterification. Compared with the shortest E3, which can hardly bind metal ion, 4.3- and 6.6-fold accelerations in the maxima were achieved in the combinations of E5/CH(3)ONa and E6/CH(3)OK, respectively. Supramolecular intermediate complex could be spectrometrically visualized by ESI-FT-ICR-MS in the course of reaction. Kinetic experiments, together with structural analyses by means of NMR, mass spectrometry, and DFT calculations of the intermediate complexes, indicate that a size-fit complex of host substitute with alkali metal ion allows strong electron withdrawing due to the close contact of the carbonyl oxygen to the metal ion, resulting in the selective rate enhancement of the reaction, while in the reaction of E3-E10 with a divalent alkaline earth metal alkoxide, (CH(3)CH(2)O)(2)Ba, the k(obs) values increased stepwise with elongation of the side arm to attain an dramatic large acceleration. In comparison with the k(obs) of E3, 4610-fold acceleration was achieved in the reaction of E10. The double activation of the host substrate and guest counter nucleophile at once brings about this extraordinary rate acceleration. The strong wrapping complexation of long oligoether ester with barium ethoxide allows for the effective electron withdrawal from the ester carbonyl group (host activation) as well as separation of the accompanying guest alkoxide anions (guest activation).