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61.
A flexible and stereodivergent synthesis of the cis- and trans-fused 2,5-disubstituted octahydroquinolinone ring systems bearing all four stereogenic centers for the synthesis of the decahydroquinoline type of dendrobatid alkaloids has been achieved. The strategy involves stereoselective and stereodivergent construction of 2,3,6-trisubstituted piperidine ring systems using the Michael type of conjugate addition reaction to the enaminoesters 1 and 3, the intramolecular aldol type of cyclization reaction of keto aldehydes 11 and 12, and ring-closing metathesis of 21 as key steps. 相似文献
62.
Hideo Nishii Toshinobu Higashimura 《Journal of polymer science. Part A, Polymer chemistry》1977,15(5):1179-1188
Ring-substituted methylstyrenes (p-, m-, and o-methylstyrenes) in conjunction with acetyl perchlorate (AcClO4) or trifluoromethanesulfonic acid as catalysts gave their linear unsaturated dimer in high yield in benzene at temperatures from 50 to 70°C. In particular, the yield of o-methylstyrene dimer was as high as 90% in the AcClO4 catalysis at 50°C. The dimer yield depended on solvent and catalyst. The terminal structures of the dimers and higher oligomers were analyzed by NMR spectroscopy. Oligomers with a cyclic terminal structure increased in the products at higher temperature. The dimer yield was improved by codimerizing p-methylstyrene with less reactive m-methylstyrene or styrene with AcClO4 catalyst. The dimers obtained partly consisted of linear unsaturated codimers. 相似文献
63.
Tetsuji Kametani Kazuo Kigasawa Mineharu Hüragi Nagatoshi Wagatsuma Setsu Saitoh Hideo Sugi 《Journal of heterocyclic chemistry》1973,10(3):313-315
Acid treatment of the alkylated products of (Va, Vb, and VIII) of piperidinols IVa and IVb, and tetrahydropyridine VII with β-bromoethylbenzene, afforded 1,2,3,4,5,6-hexahydro-8-hydroxy-2,6-methano-6,1 1-dimethyl-3-phenethyl-3-benzazocine (la) in good yield. Piperidinols Va and Vb were also obtained from the reaction of N-(3-methyl-3-pentenyl)-β-phenethylamine (IIb) with methyl 3-(4-methoxyphenyl)-2,3-epoxypropionate. 相似文献
64.
Hideo Kise Hiroshi Ogata 《Journal of polymer science. Part A, Polymer chemistry》1983,21(12):3443-3451
The reaction of poly(vinylidene fluoride) (PVDF) powder with aqueous sodium hydroxide solutions in the presence of quaternary ammonium or phosphonium halides as phase transfer catalysts afforded dehydrofluorinated polymers. The structure of the products was investigated by infrared spetroscopy, and a fluorine-substituted conjugated polyene structure was suggested which was found to be stable against air oxidation. Tetrabutylammonium bromide and tetrabutylphosphonium bromide were the most active among the catalysts used. The effects of the reaction conditions on the conversion are described. The treatment of PVDF films under phase transfer conditions increased the wettability of the surface and electric conductivity. The reaction of PVDF with potassium hydroxide in 2-propanol proceeded not only by elimination but also by substitution of hydroxide ions. 相似文献
65.
A stereoselectivity in an intramolecular cycloaddition of the olefinic -quinodimethanes 13 and 23 generated from the thermolysis of optically active 4β-[2-(4-methoxybenzocyclobutenyl)ethyl] -5α-methoxymethyl-3-phenyl-thio-methylenefuran-2-ones 12 and 22, respectively, is studied and a stereoselective synthesis of (+)--4,5-( 4-methoxybenzo) -1β,7aβ-(2α-methoxymethyl-5-oxofuro)hydrindane 1 is also described. 相似文献
66.
Polyanionic glycopolymers were synthesized aiming at establishing a simple process for assembling glycosyl arrays. The synthetic glycopolymers carry the key carbohydrate epitopes of α-d-galactobioside (Gb2), β-lactoside, and α-d-mannopyranoside, each of which serves as a ligand of bacterial toxins and adhesion proteins. The Gb2 epitope, prepared from penta-O-acetyl-d-galactopyranose, was coupled with poly(ethylene-alt-maleic anhydride) in a polymer reaction to afford a Gb2-embedded glycopolymer having also carboxylate (COO−) polyanions at the side chain. The polyanionic glycopolymer was then applied to a preparation of sugar-coated gold electrodes, which involves an alternating layer-by-layer adsorption based on electrostatic interactions. The presence of the Gb2-coat on the surface was evidenced by Fourier transform infrared reflection absorption spectroscopy. The Gb2-coated glyco-chip was stable in 10 mM HEPES buffer containing 150 mM NaCl aq. Other glycopolymers carrying the β-lactoside and α-d-mannopyranoside epitopes were applied to the same assembling process. The derived glycosyl arrays will be useful for detecting Shiga toxins, other pathogenic toxins and viruses when applied as glyco-chips for surface plasmon resonance or quartz crystal microbalance technique. 相似文献
67.
A novel synthesis of 5-cyano[n](2,4)pyridinophane-6-ones 12a-d (n= 9, 8, 7, and 6) consists of allowing cyanoacetatoamide to react with cycloalk-2-enones. Their static and dynamic properties as well as structural characteristics are studied on the basis of their spectroscopic properties, cyclic voltammetry, and theoretical calculations. The (1)H and (13)C NMR spectra at various temperatures have clarified the dynamic behavior of the methylene chains for [7](2,4)- and [6](2,4)pyridinophane-6-one derivatives 12c and 12d. The energy barrier (Delta G(++)) of the bridge flipping of 12c is estimated to be 12.0 kcal mol(-1)(T(c)= 0 degree C). On the other hand, compound 12d undergoes pseudorotation (conformational change of the methylene chain) at room temperature, and does not undergo bridge flipping even at 150 degree C in DMSO-d(6). The energy barrier (Delta G(++)) of the pseudorotation of the methylene chain 12d of is found to be 10.5 kcal mol(-1)(T(c)=-25 degree C), and thus, two stable conformers of the hexamethylene bridge of 12d are determined as predicted by theoretical calculations. Deformation of the pyridone ring of 12d is also determined by X-ray crystallographic analysis. Furthermore, chemical transformations of 12a-c leading to 5-carbamoyl[n](2,4)pyridinophanes 15a-c are also accomplished successfully in moderate to good yields. 相似文献
68.
Kazuhiro Endo Hideo Ihara Kazuhiro Watanabe Shun-Ichi Gonda 《Journal of solid state chemistry》1981,39(2):215-218
Transition-metal trisulfides, TiS3, NbS3, and TaS3, with a quasi-one-dimensional structure are investigated by X-ray photoelectron spectroscopic (XPS) measurements to obtain information on the valence band structures. The band structures at the Fermi level of these compounds correspond well to their transport properties. A shoulder is observed at the top of the valence band in NbS3 and TaS3, suggesting that this band is made up of the metal dz2 electrons. The dz2 band is occupied in NbS3 and TaS2 and empty in TiS3. The characteristic features at the top of the valence band in NbS3 imply the occurrence of dz2 band separation, which leads to a semiconducting nature. 相似文献
69.
The enzymatic resolution products [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-7 (98% ee) and {acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal} (8aS)-9 (>99% ee)] obtained by the lipase-catalyzed enantioselective acetylation of (±)-7 in the presence of vinyl acetate as an acyl donor were converted to the ,β-unsaturated ketones (8aR)-6 and (8aS)-6, respectively. Concise syntheses of (+)-totarol 1, (+)-podototarin 2 and (+)-sempervirol 3 were achieved based on Michael reactions between (8aS)-6 and the appropriate β-keto ester followed by aldol condensation. The first chiral syntheses of (+)-jolkinolides E 4 and D 5 were achieved from (5R,10R,12R)-12-hydroxypodocarpa-8(14)-en-13-one 15 derived from (8aR)-6. 相似文献
70.