The remote-oxyfunctionalization of unactivated carbons in (5 beta)-3-oxobile acids by 2,6-dichloropyridine N-oxide catalyzed by ruthenium-porphyrin and HBr: a direct lactonization at C-20

Remote-oxyfunctionalization induced by 2,6-dichloropyridine N-oxide (DCP N-oxide) as an oxygen donor and a (5,10,15,20-tetramesitylporphyrinate) ruthenium(II) carbonyl complex (Ru-porphyrin) and HBr as catalysts was examined for a series of methyl ester-peracetylated derivatives of (5 beta)-3-oxobile acids. Using the DCP-N-oxide/Ru-porphyrin/HBr system, 5 beta-hydroxylation predominated for the substrates having a 12-acetoxyl substituent due to steric hindrance, but the presence of a 7-acetoxyl substituent decreased the reactivity of the 5 beta-position allowing for the competitive (20S)-20-oxyfunctionalization, subject to electronic constraints. A variety of novel 5 beta-hydroxylation and (20S)-24,20-gamma-lactonization products, as well as their double-oxyfunctionalization and dehydration products, were obtained in one-step. The alkaline hydrolysis of the gamma-lactones gave the corresponding stereoselective (20S)-20-hydroxy-carboxylic acids.     

Novel method for linking CdS nanoparticles at liquid-liquid interface

Liquid-liquid interface of water-hexane provides a unique reaction environment in which CdS nanoparticles capped with mercaptoethylamine could be linked together to form a homodimer with a divalent acid chloride, sebacoyl chloride. Prior to the reaction, mercaptoethylamine-capped CdS in aqueous solution was purified by dialysis and freeze-drying. The observation with a transmission electron microscope suggested the formation of a homodimer of CdS nanoparticles.     

Cytotoxic cholic acid type sterones from a marine soft coral <Emphasis Type="Italic">Paraminabea</Emphasis> sp.

Chemical investigation of an Okinawan marine soft coral resulted in the isolation of one new compound (1) and five known cholic acid type keto-steroids 2–6 possessing enone or dienone A-rings and desmosterol (7). The structures of all compounds were elucidated from spectral data, mainly by 1D and 2D NMR techniques, mass spectra, comparison of NMR data with those of reported compounds, and by chemical transformations. Compounds 1–7 showed potent cytotoxic activity.     

Catalytic asymmetric oxidation of cyclic dithioacetals: highly diastereo- and enantioselective synthesis of the S-oxides by a chiral aluminum(salalen) complex

Aluminum(salalen) complex 1 [salalen = half-reduced salen, salen = N,N'-ethylenebis(salicylideneiminato)] was found to be a highly efficient catalyst for asymmetric oxidation of cyclic dithioacetals in the presence of 30% hydrogen peroxide as an oxidant. In the reaction of a series of 2-substituted 1,3-dithianes bearing alkyl, alkenyl, alkynyl, and aryl groups as the substituent, the trans-monoxides were obtained in high yields with 19:1 → >20:1 dr (diastereomeric ratio) and 98-99% ee (enamtiomeric excess). The reaction of nonsubstituted 1,3-dithiane also proceeded in a highly enantioselective manner to give the monoxide with a small formation of the trans-1,3-dioxide, an overoxidation product. Five-membered 1,3-dithiolanes and seven-membered 1,3-dithiepanes also underwent oxidation to give monoxides with high diastereo- and enantioselectivity. It was found that the equilibrium between the two chairlike conformers of dithianes has relevance to the observed diastereoselectivity in the first oxidation process, and the dioxide formation in the oxidation of 1,3-dithiane and its stereochemistry also can be explained by the conformational equilibrium of the product monoxide.     

Self‐Directed Orientation of Molecular Columns Based on n‐Type Hexaazatrinaphthylenes (HATNAs) for Electron Transport

Self‐organizing n‐type hexaazatrinaphthylenes (HATNAs) with various bay‐located side chains have been synthesized. The HATNA derivatives are able to form long‐range molecular columns with self‐directed growth directions. In particular, alkyl‐substituted HATNAs showed in‐plane molecular columns with axes parallel to substrates, whereas the columnar orientation of the HATNAs with alkylethynyl or alkylthio groups strongly depended on the length of the introduced side chains. Interestingly, the derivative with octylthio chains exhibited out‐of‐plane molecular columns, in which electron mobility of up to 10^?3 cm² V^?1 s^?1 was determined through the time‐of‐flight technique, highlighting the fact that such molecular columns based on bay‐substituted HATNAs are promising n‐type semiconductors for device applications.     

Multidimensional angle sensing method using guided-mode resonance

Optical Review - A waveguide grating on a transparent substrate can serve as an optical notch filter owing to guided-mode resonance. The filtering wavelength is highly sensitive to an incidence...     

Visual colorimetry for trace antimony(V) by ion-pair solid-phase extraction with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) on a PTFE type membrane filter.

A new visual colorimetry for trace antimony(V) based on ion-pair solid-phase extraction to a PTFE-type membrane filter with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) ion ([Co(5-Cl-PADAP)(2)](+)) has been developed. Experiments showed that hexachloroantimonate(V) ion (SbCl(6)(-)) was adsorbed with [Co(5-Cl-PADAP)(2)](+) to the front surface of the PTFE filter. The adsorption of antimony(V) ion was promoted by the addition of lithium chloride as a source of chloride ion. The excess reagent of [Co(5-Cl-PADAP)(2)](+) was eluted by rinsing with a 10 wt% methanol aqueous solution. In this case, the slow rate of the hydrolysis reaction of SbCl(6)(-) and the difference of the hydrophobicity of the ion pairs were important for adsorption and separation with a PTFE-type membrane filter. The antimony(V) concentration was determined through a visual comparison with a standard series. The visual detection limit was 0.10 microg. The calibration curve assessed with the reflection spectrometric responses at 580 nm was linear in the concentration range of 0.10 - 1.2 microg (r = 0.996). The proposed method has been applied to the determination of sub-microgram levels of antimony(V) ion in water samples.