A micellar alignment effect in the photodimerizations of N-ω-carboxyalkyl-2-pyridones and their 4-alkyl derivatives in micelle or reversed micelle

The photoreaction of N-ω-carboxyalkyl-2-pyridones at 7.2–22.4mM concentrations in micellar and reversed micellar systems gave the ratio of cis to trans dimer increasing with decreasing length of the alkyl chain and in their 4-alkyl derivatives, only cis dimer was obtained.     

Thermomechanical analysis of calcium alginate hydrogels in water

Spherical hydrogels of Ca alginate (CaAlg) were prepared by conversion of Na alginate (NaAlg) to CaAlg in CaCl₂ aqueous solution. The degree of conversion was varied by changing the conversion times. NaAlg samples with mannuronic and guluronic component ratios (M/G ratio) 0.21 and 0.88 were used. The degrees of conversion and water contents (W_c=mass of water in CaAlg/mass of dry CaAlg) were measured by weighing. The degrees of conversion from NaAlg to CaAlg increased with increasing immersion time and the content of G. W_c of CaAlg hydrogels decreased with increasing immersion time and levelled off at 75 g g^-1 when immersion time exceeded about 10 min. Viscoelastic properties of CaAlg hydrogels in water were measured using a thermomechanical analyzer (TMA) equipped with a quartz compression probe. Dynamic modulus (E') of CaAlg with M/G=0.88 increased with increasing immersion time when immersion time is less than 5 min. When immersion time exceeded 5 min, E' reached a constant value at 4.5*10⁴ Pa. In contrast, E' of CaAlg with M/G=0.21 increased with increasing immersion time. This suggests that densely crosslinked hydrogels are formed when the guluronate sequence of the samples is rich and Na ions are fully converted to Ca ions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrostatic manipulation of enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate within gamma-cyclodextrin cavity through chemical modification. inverted product distribution and enhanced enantioselectivity

In the enantiodifferentiating supramolecular photocyclodimerization of 2-anthracenecarboxylate using gamma-cyclodextrin with a dicationic side chain, a dramatic switching of the product selectivity and a significant enhancement of the enantiomeric excess were achieved by introducing a flexible dicationic sidearm to native gamma-cyclodextrin and also by lowering the temperature and solvent polarity.     

Cobalt-catalyzed intramolecular Heck-type reaction of 6-halo-1-hexene derivatives

[reaction: see text] Treatment of 6-iodo-1-hexene derivatives with trimethylsilylmethyl Grignard reagent in the presence of CoCl(2)(dppb) in refluxing THF affords Heck-type products, methylenecyclopentanes, in good yields.     

Analysis of crystalline phases in airborne particulates by grazing incidence X-ray diffractometry

Amounts of crystalline phases of airborne particulates collected on a silicon wafer (10 x 10 mm) using a high-volume air sampler were analyzed by grazing incidence X-ray diffractometry (GIXD). Airborne particulates were classified into five size ranges (1.09-10.5 microm) with a cascade impactor attached on the sampling ports of the high-volume air sampler. GIXD was used throughout this analysis to obtain better sensitivity for small amounts of airborne particulates on the silicon wafer. Calibration standards on the silicon wafer for the diffractometric determination were prepared by the suspension droplet method of the crystalline standards dispersed in cyclohexane. Analytical lines were (020) for gypsum, (101) for quartz, (104) for calcite, (200) for halite, and (110) for sal ammoniac. The sample and the calibrating standards were heated at 350 degrees C for 2 h to avoid mutual interference with gypsum (041 and 221) when calcite and halite were determined. The GIXD method enables us to determine 0.23-13.2 microg of gypsum, quartz, calcite, halite and sal ammoniac in 0.110-0.233 mg of airborne particulates on the silicon wafer.     

Cobalt schiff base complex catalysed solvolytic ring opening of epoxy compounds

Co(salen) catalyzes solvolytic ring opening of epoxy compounds in methanol to give glycol monomethyl ether derivatives. Active species is Co(salen) (OH) which is formed in situ, and its catalytic activity depends on the pKa of the conjugated acid of X in Co(salen) (X) (X=OAc, OCH₂CF₃, OH).

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() , . ()(OH), in situ X () (X) ( X=OAc, OCH₂CF₃, OH).

     

Effect of ultraviolet irradiation on terpolymerization of sulfur dioxide with two unsaturated compounds

The terpolymerization of sulfur dioxide, butene-1 and acrylonitrile affords terpolymers containing equimolar amounts of sulfur dioxide and butene-1 with various acrylonitrile contents. Ultraviolet irradiation was found to accelerate the polymerization and decrease the acrylonitrile content in the polymer. This fact is interpreted by a mechanism through a copolymerization of sulfur dioxide–butene-1 complex and acrylonitrile, whereby the polymerizability of sulfur dioxide–butene-1 complexed monomer may be accelerated by ultraviolet light. In fact, a binary system of sulfur dioxide and butene-1 was found to be accelerated by ultraviolet irradiation, and it affords a maximum rate at a 1:1 composition of feed monomer. Ultraviolet light of 250–300 mμ wavelength is effective for the initiation and the propagation. This may be ascribed to the ultraviolet absorption of the sulfur dioxide–butene-1 complex. The temperature coefficient was measured in both dark and ultraviolet irradiation reactions. The ultraviolet irradiation enhances the reactivity of sulfur dioxide–butene-1 complexed monomer at low temperature. In the terpolymerization with sulfur dioxide, isoprene, and butadiene, the ratio of isoprene and butadiene in the terpolymer was not altered by ultraviolet irradiation because both monomers from complexes with sulfur dioxide, perhaps having the same temperature coefficient for the polymerization.     

A novel method for the preparation of benzylidenecyclohexanes with high optical purity

The enantioselective reaction of the α-thio carbanion derived from 1-phenyl-1-(phenylthio)-1-(tributylstannyl)methane with 4-substituted cyclohexanones in the presence of bis(oxazoline)s gave the products as a diastereomeric mixture. Each diastereomer obtained had high optical purity. The reaction of the α-seleno carbanion derived from the bis(phenylseleno)acetal also showed high enantioselectivity. The stereospecific elimination of the isolated diastereomers on treatment with methanesulfonyl chloride and triethylamine afforded axially chiral benzylidenecyclohexanes with high enantioselectivities up to 99% ee.     

Total synthesis of scytophycin C. 1. Stereoselective syntheses of the C(1)-C(18) segment and the C(19)-C(31) segment

[structure: see text] Stereoselective total synthesis of scytophycin C, a marine 22-membered macrolide displaying potent activity against a variety of human carcinoma cell lines, has been reported in which the polypropionate structure bearing contiguous asymmetric centers was stereospecifically constructed by using new acyclic stereocontrol. This paper describes stereoselective syntheses of the C(1)-C(18) segment (Segment A) including a trans-disubstituted dihydropyran ring and the C(19)-C(31) segment (Segment B) having eight stereogenic centers.     

Chemical forms of radioactive iodine in seawater and its effects upon marine organisms

Chemical forms of radioactive iodine and its effects upon marine organisms were studied by the tracer experiments. Seaweeds or fish were held in the aquarium in which the 125I tracer in either iodide or iodate form was inoculated. Iodide form of 125I was taken by Dorome (Chasmichthys gulosus) with the concentration factor of about 10 and excreted with the biological half-life of 15 days, while iodate form of 125I was not taken up appreciably and the concentration factor did not greatly exceed unity. Uptake and loss of 125I were studied as well for 3 species of seaweeds, Hijiki(Hizikia fusiforme), Nejimoku (Sargassum sagamianum) and Tsunomata (Chondrus ocellatus). Iodate form of 125I was accumulated less than iodide form by these seaweeds but the concentration factor of iodate by these seaweeds was very high compared to those by fish.