Crowned polyacetylene. I. Synthesis and characterization of poly(4′-ethynylbenzo-15-crown-5)

4′-Ethynylbenzo-15-crown-5 ( EB15C5 ) polymerized with high yields in the presence of (bicyclo[2.2.1] hepta-2,5-diene) rhodium(I) chloride dimer and triethylamine as a cocatalyst in chloroform at 30°C. Common catalysts for the polymerization of substituted acetylenes, WCl₆ and MoCl₅, did not produce any polymer from EB15C5 . The structure of the main chain for poly(4′-ethynylbenzo-15-crown-5) ( PEB15C5 ) was determined to be predomi-nantly cis form, based upon the relatively sharp signals attributed to the main chain atoms that was observed in the ¹H and ¹³C NMR spectra. The cation-binding properties of PEB15C5 are very similar to that of poly(4′-vinylbenzo-15-crown-5), and the selectivity is in the order of K⁺> Rb⁺ ? Cs⁺ ? Na⁺, Li⁺. The electrical conductivity of PEB15C5 increased from 1.3 × 10^?10 to 1.3 × 10^?6 S. cm^?1, when the polymer was doped with iodine. © 1995 John Wiley & Sons, Inc.     

Crowned polyacetylene. 2. cis form determination of poly(4′-ethynylbenzo-15-crown-5) by solid-state NMR method

The chain structure of cis-poly(4′-ethynylbenzo-15-crown-5) (PEB15C5), prepared using the rhodium complex catalyst, was studied at ?175°C using the solid-state NMR technique. The second moment of PEB15C5 was 7.0 G² for the main chain and 19.0 G² for the side chain. These values agreed well with the respective theoretical ones for the cis form in the rigid state rather than the trans one. This agreement between experiment and theory suggested that the plane of the side chain (i.e., the benzo-15-crown-5 group) is orthogonal to the main chain plane of the cis-transoidal form. It was verified that the strong dipoledipole interaction between the side chains plays an important role as a clue to theoretically determine the cis-transoidal form. NMR results in solid state confirmed theoretically that multipeaks in the ¹H and ¹³C NMR spectra in CDCl₃ solution are attributed to cis-transoidal form in the chain. © 1995 John Wiley & Sons, Inc.     

Astellifadiene: Structure Determination by NMR Spectroscopy and Crystalline Sponge Method,and Elucidation of its Biosynthesis

Genome mining of a terpene synthase gene from Emericella variecolor NBRC 32302 and its functional expression in Aspergillus oryzae led to the production of the new sesterterpene hydrocarbon, astellifadiene ( 1 ), having a 6‐8‐6‐5‐fused ring system. The structure of 1 was initially investigated by extensive NMR analyses, and was further confirmed by the crystalline sponge method, which established the absolute structure of 1 and demonstrated the usefulness of the method in the structure determination of complex hydrocarbon natural products. Furthermore, the biosynthesis of 1 was proposed on the basis of isotope‐incorporation experiments performed both in vivo and in vitro. The cyclization of GFPP involves a protonation‐initiated second cyclization sequence, 1,2‐alkyl migration, and 1,5‐hydride shift to generate the novel scaffold of 1 .     

Astellifadiene: Structure Determination by NMR Spectroscopy and Crystalline Sponge Method,and Elucidation of its Biosynthesis

Genome mining of a terpene synthase gene from Emericella variecolor NBRC 32302 and its functional expression in Aspergillus oryzae led to the production of the new sesterterpene hydrocarbon, astellifadiene ( 1 ), having a 6‐8‐6‐5‐fused ring system. The structure of 1 was initially investigated by extensive NMR analyses, and was further confirmed by the crystalline sponge method, which established the absolute structure of 1 and demonstrated the usefulness of the method in the structure determination of complex hydrocarbon natural products. Furthermore, the biosynthesis of 1 was proposed on the basis of isotope‐incorporation experiments performed both in vivo and in vitro. The cyclization of GFPP involves a protonation‐initiated second cyclization sequence, 1,2‐alkyl migration, and 1,5‐hydride shift to generate the novel scaffold of 1 .     

Doyle-Kirmse reaction of allylic sulfides with diazoalkane-free (2-furyl)carbenoid transfer

[reaction: see text] In the presence of rhodium catalyst, (2-furyl)carbenoids generated from conjugated ene-yne-carbonyl compounds 1 efficiently undergo carbene transfer reactions with allylic sulfides followed by [2,3]sigmatropic rearrangement of sulfur ylides to give furan-containing sulfides in good yields. When diallyl sulfide is employed, heteroatom-containing polycyclic compounds are obtained by sequential intramolecular Diels-Alder cyclization reaction with a constructed furan ring as an enophile.     

A comparative visualization tool for ocean data analysis based on mode water regions

Journal of Visualization - Ocean data have been improved with the enhancement of observed values and the evolution of computational technologies. It has also been verified based on the...     

Fixed crosslink formation and viscoelasticity of polystyrene networks

The crosslinking formation in the 8/92 mol % random copolymer of ethynyl- styrene and styrene is clarified quantitatively from the IR spectrum analysis on the basis of the thermally homogeneous reaction of ethynylstyrenes between the chains. The viscoelastic properties of the crosslinked polystyrene, CL-P(ESt/St), are investigated based on the temperature and frequency dependencies of the dynamic Young modulus. The relaxation spectrum of CL-P(ESt/St) drops deeply like the Wedge type with a slope of −½ in the glass transition region, and became a plateau without a terminal zone in the rubbery elasticity region. The effects of the ethynyl crosslinked junctions for the micro-Brownian motions of the segments in the strand are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3319–3327, 1999     

Dextran oxidized by a malaprade reaction shows main chain scission through a maillard reaction triggered by schiff base formation between aldehydes and amines

Although periodate‐oxidized dextran is widely used in biomedical applications, the degradation mechanism of oxidized dextran has not yet been elucidated. Herein, we propose a novel main chain scission mechanism of oxidized dextran triggered by reaction with amine. NMR analysis revealed four hemiacetal substructures during oxidation by periodate. Kinetic analysis showed that the degradation time constant of the C3‐removed substructure and increasing time constant of the reducing end protons are consistent with the decrease in molecular weight determined by gel permeation chromatography. A methylene group is generated at the same time constant of degradation, indicating that oxidized dextran degradation proceeds via a Maillard reaction. Oxidized dextran does not degrade in saline solution without reactive amine species. Thus, we conclude that oxidized dextran is degraded in the main chain via Schiff base formation through a Maillard reaction, depending on the oxidation ratio and amino acid concentration. These findings help to elucidate the reaction mechanism of polysaccharide degradation and develop novel biodegradable polysaccharide materials for biomedical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2254–2260     

ABA- and BAB-triblock cooligomers of tri-<Emphasis Type="Italic">O</Emphasis>-methylated and unmodified cello-oligosaccharides: syntheses and structure-solubility relationship

Triblock cooligomers consisting of tri-O-methyl-glucopyranosyl and unmodified glucopyranosyl residues, methyl 2,3,4,6-tetra-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-α-d-glucopyranoside (1: ABA triblock cooligomer; DS = 2.1) and β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-2,3,6-tri-O-methyl-β-d-glucopyranosyl-(1 → 4)-d-glucopyranose (2: BAB triblock cooligomer; DS = 1.8) were prepared. Compound 1 dissolved both in distilled water and chloroform but compound 2 dissolved in distilled water not in chloroform, though compounds 1 and 2 consist of 4 tri-O-methyl-glucopyranosyl and 2 unmodified anhydro glucopyranosyl units.