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31.
Shimpei Sugiyama 《Tetrahedron letters》2005,46(39):6771-6775
Treatment of optically active 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from symmetrical ketones and (R)-(−)-chloromethyl p-tolyl sulfoxide in three steps, with lithium enolate of carboxylic acid tert-butyl esters gave optically active adducts having a substituent at the α-position with high 1,4-chiral induction from the sulfur chiral center in high yields. The adducts were converted to optically active esters and carboxylic acids having a chiral center at the α-position. When this addition reaction was carried out with the ester enolate generated from excess carboxylic acid tert-butyl ester with LDA in the presence of HMPA, the diastereomer of the adduct was obtained. By using the two reaction conditions for the generation of the ester enolates, a new method for asymmetric synthesis of both enantiomers of carboxylic acid derivatives having a substituent at the α-position from the one chiral source, (R)-(−)-chloromethyl p-tolyl sulfoxide, was realized. 相似文献
32.
Y Naito T Goto F Akahoshi S Ono H Yoshitomi T Okano N Sugiyama S Abe S Hanada M Hirata 《Chemical & pharmaceutical bulletin》1991,39(9):2323-2332
A series of 2-[4-(thiazol-2-yl)phenyl]propionic acids substituted at various positions were prepared by the reaction of diethyl 2-methyl-2-(4-thiocarbamoylphenyl)malonates with alpha-bromoaldehyde diethyl acetals or alpha-haloketones followed by hydrolysis of esters. The inhibition of prostaglandin H synthetase (cyclooxygenase) was assayed by use of an enzyme preparation from guinea pig polymorphonuclear leukocytes. Examination of the structure-activity relationship of these compounds indicated that the substitution pattern with halogens at position 3 (R1) of the benzene ring and a methyl group in position 4 (R2) and/or 5 (R3) of the thiazole ring were favorable for inhibitory activity. The compounds bearing bulky alkyl or polar functional groups at the R2 position were weak inhibitors. The potent inhibitors of cyclooxygenase were tested for their ability to reduce carrageenin-induced inflammation of rat paws. These derivatives had strong anti-inflammatory activity based on their strong inhibition of cyclooxygenase, with some exceptions, including those with a thiomethyl group at R1. 相似文献
33.
Adachi K Sugiyama Y Yoneda K Yamada K Nozaki K Fuyuhiro A Kawata S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6616-6628
Novel triply hydrogen bonded suprastructures based on [M(tdpd)2(L)2]2- (H2tdpd=1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile, L=solvent) and melamine-analogous cations have been synthesized and characterized. The use of anions containing two AAA sets from [M(tdpd)2(L)2]2- together with cations containing one DDD set (A=hydrogen-bond acceptor, D=hydrogen-bond donor) leads to the formation of complementary triply hydrogen bonded modules in the solid state. In all cases, the building module is further extended via additional hydrogen-bonding interactions to produce a tape, and tapes are assembled into sheets. These results show that a hydrogen-bonded module consisting of different kinds of building blocks, one of which is a metal complex that includes hydrogen-bond acceptor sites and the other is a hydrogen-bond donor molecule, will be attractive for constructing metal-containing supramolecular systems by the self-assembly technique. 相似文献
34.
Mitsuru Ueda Yoshikatu Seino Yuko Haneda Masanobu Yoneda Jun-Ichi Sugiyama 《Journal of polymer science. Part A, Polymer chemistry》1994,32(4):675-681
tert-Butyl substituted poly (aryl ether ketone)s with relatively high molecular weights were prepared by the Ni-catalyzed polymerization of tert-butyl substituted aromatic dichlorides containing ether ketone unit. These polymers were amorphous and soluble in common organic solvents, such as THF, dichloromethane, and chloroform. De-tert-butylation of the polymer by the treatment of trifluoromethanesulfonic acid in the presence of toluene proceeded smoothly and produced crystalline poly (aryl ether ketone). © 1994 John Wiley & Sons, Inc. 相似文献
35.
Sugiyama T Schweinberger E Kazimierczuk Z Ramzaeva N Rosemeyer H Seela F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(2):369-378
2-Aza-2'-deoxyadenosine (2, z2Ad) is synthesized via its 1,N6-etheno derivative 7 and enzymatically deaminated to 2-aza-2'-deoxyinosine (3). Compound 2 is converted into the phosphoramidite building block 10b. This is employed in solid-phase oligonucleotide synthesis. The 2-azapurine base forms a strong base pair with guanine, but a much weaker one with adenine, thymine, and cytosine. Oligonucleotide duplexes with dangling nucleotide residues, such as 2-aza-2'-deoxyadenosine and 7-deaza-2'-deoxyadenosine (4, c7Ad), either on one or both termini, are synthesized, and the thermal stability of the duplexes is correlated with the hydrophobic properties of the dangling nucleotide residues. 相似文献
36.
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38.
An air-segmented continuous-flow method has been developed for the determination of molybdenum at ultra trace levels using
the catalytic effect of molybdate during the oxidation of L-ascorbic acid by hydrogen peroxide. Incorporation of an on-line
ion exchange column improved the tolerance limit for various ions. The detection limits with and without the column were 64 pmol L−1 and 17 pmol L−1, and the reproducibilities at 10 nmol L−1 were 2.1% and 0.2%, respectively. The proposed method was applied to the determination of molybdenum in seawater and lake
water as well as in rock and sediment samples. This method has the highest sensitivity among the available literature to our
knowledge, and is also convenient for routine analysis of molybdenum in various natural samples.
Author for correspondence. E-mail: masahito.sugiyama@ sojin0206.mbox.media.kyoto-u.ac.jp
Received October 23, 2002; accepted January 28, 2003
Published online May 19, 2003 相似文献
39.
Detailed investigation on the origin of the acidity of the alpha-protons of a set of the carbonyl molecules was carried out on the basis of properties of the localized molecular orbital. An anomalously high acidity of Meldrum's acid, as compared with those of dimedone and dimethyl malonate, is one of the well-known but unresolved issues. The well-localized sigma orbitals of the C-H bonds at the alpha-position of the carbonyl groups can be obtained with the reactive hybrid orbital (RHO) theory. We found that the energy levels of the unoccupied RHOs of the C-H moiety of Meldrum's acid and other carbonyl compounds showed a good linear correlation with the experimental deprotonation energies. This is probably because the deprotonation reaction to form the proposed naked anions in a polar solvent is a highly endothermic process, in which the thermodynamic energy differences between the neutral molecules and the corresponding anions approximately coincide with the activation energies. We also investigated the effect of the conformational change upon deprotonation on the electron-accepting energy level of the relevant C-H bonds of cyclic/acyclic and monocarbonyl/dicarbonyl compounds. A conformational change occurs in the cases of cyclic six-membered compounds, but its influence on the reactivity of the C-H bond is small. The acidity of dicarbonyl compounds, including Meldrum's acid, showed a good correlation with the deviations from the perpendicular position of the dihedral angles of the relevant C-H bond with respect to the adjacent carbonyl C=O bond. This angle parameter can be related to the magnitude of the in-phase orbital interaction between the sigma(CH) and pi(C)(=)(O) orbitals, which facilitate electron acceptance. These results indicated that the acidity of the alpha-proton of carbonyl compounds can be represented in terms of the electron-accepting orbital levels of the unoccupied RHO of the C-H moiety. All the linear relationships found in the present work strongly suggested that the acidity of Meldrum's acid, which is conventionally regarded as an anomaly, is consistent with those of the other carbonyl compounds. 相似文献