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排序方式: 共有192条查询结果,搜索用时 15 毫秒
1.
Huang JM Yang CS Zhao R Takahashi H Fukuyama Y 《Chemical & pharmaceutical bulletin》2004,52(1):104-107
Seven new seco-prezizaane-type sesquiterpenes were isolated from the methanol extract of the pericarps of Illicium merrillianum. Their structures were elucidated as 3-deoxypseudoanisatin (1), 2beta-hydroxy-3,6-dedioxypseudoanisatin (2), 8alpha-hydroxy-10-deoxycyclomerrillianolide (3), 10beta-hydroxypseudoanisatin (4), 10beta-hydroxycyclopseudoanisatin (5), 1,6-dihydroxy-3-deoxyminwanensin (6), and 8-deoxymerrilliortholactone (7) by analyses of their spectroscopic data and chemical transformation. Compounds 4 and 5 as well as 6 and 7 coexist as a keto/acetal equilibrated mixture in methanol solution. 相似文献
2.
Kei Yoshida Junko Kusaki Katsunobu Ehara Shiro Saka 《Applied biochemistry and biotechnology》2005,123(1-3):795-806
Japanese beech (Fagus crenata Blume), its cell wall components, and model compounds were treated by supercritical water (380°C, 100 MPa) for 5 s using a batch-type reactor to investigate the production behavior of low molecular weight organic acids. It was found that cellulose and hemicellulose were decomposed to formic acid, pyruvic acid, glycolic acid, acetic acid, and lactic acid, whereas lignin was barely decomposed to such organic acids under the given conditions. However, after prolonged treatment (380°C, 100 MPa, 4 min) of lignin, some organic acids were recovered owing perhaps to the decomposition of the propyl side chain of lignin. It was additionally revealed that the predominant organic acid recovered was acetic acid, which might be derived from the acetyl group of hemicellulose in Japanese beech. 相似文献
3.
Yoshiyasu Ichikawa Yohei Matsukawa Mari Tamura Fumiyo Ohara Minoru Isobe Hiyoshizo Kotsuki 《化学:亚洲杂志》2006,1(5):717-723
A new method for the synthesis of urea‐linked disaccharides in aqueous media has been developed. The key feature of our approach is two strained Steyermark‐type gluco‐ and galactopyranosyl oxazolidinones. Each oxazolidinone is attached to a pyranose ring in a di‐equatorial trans‐annulation framework. Reaction of these oxazolidinones with 4‐aminohexopyranose in water proceeded smoothly to afford the urea‐tethered cellobiose and lactose analogues. The galactose‐type oxazolidinone proved to be more reactive than the glucose‐type, which is explained by the presence of an axial hydroxy group at C4 in the former. 相似文献
4.
Inhibitory activities of Dipyridamole (DPM, 2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido(5,4-d)py rim idine) against xanthine oxidase (XO), carbonic anhydorase (CA) and monoamine oxidase (MAO) were studied, in vitro. DPM did not inhibit XO and CA, but it strongly inhibited MAO. The type of inhibition by DPM against MAO with respect to benzylamine as a substrate was uncompetitive. 相似文献
5.
Takahasi H Yanagi K Ueda M Nakade K Fukuyama Y 《Chemical & pharmaceutical bulletin》2003,51(12):1377-1381
The methanol extract of the seeds of Phytolacca americana was reinvestigated to yield three new 1,4-benzodioxane-type compounds, americanoic acid methyl ester (1), isoamericanoic acid A methyl ester (2), and 9'-O-methylamericanol A (3) along with the previously isolated neolignans 6-9. The structures of 1-3 were characterized by 2D NMR and long-range selective proton-decoupling (LSPD) techniques. The neuritogenic effects of compounds 1-3, and dicarboxilic acids 4 and 5, which had been previously synthesized with horseradish peroxidase-catalyzed oxidative coupling of caffeic acid, were examined in primary cultured rat cortical neurons. Americanoic acid A methyl ester (1) exhibited neurite outgrowth-promoting activity at concentration of 0.01-1.0 microM, whereas dicarboxilic acids 4 and 5 were found to induce neuritogenesis dose dependently at the concentrations from 0.1 microM to 10 microM. 相似文献
6.
Fukuyama Y Minami H Matsuo A Kitamura K Akizuki M Kubo M Kodama M 《Chemical & pharmaceutical bulletin》2002,50(3):368-371
New five seven-membered vibsane-type diterpenes named 5-epi-vibsanin C, 5-epi-vibsanin H, 5-epi-vibsanin K, 18-O-methyl-5-epi-vibsanin K and 5-epi-vibsanin E have been isolated from the leaves of Viburnum awabuki (Caplifoliaceae). Their structures have been elucidated by analyses of spectroscopic data and comparison of their spectral data with those of the previously known seven-membered vibsane-type diterpenes. The occurrence of these seven-membered vibsane-type diterpenes with a cis relationship on the C-5 and C-10 positions in nature have been predicted by conformational analysis of vibsanin B, an eleven-membered vibsane-type diterpene. Vibsanin C, 5-epi-vibsanin C and 5-epi-vibsanin H exhibited moderate cytotoxic activities on KB cells. 相似文献
7.
A new synthetic method for the preparation of allyl amines has been developed. The key steps of this method are enantioselective addition of diethylzinc and [1,3]-chirality transfer through the [3.3] sigmatropic rearrangement of allyl cyanates. Stereocontrolled syntheses of lentiginosine (1) and polyoxamic acid derivative 2 from a common intermediate 7 derived from D-tartaric acid (8), have been accomplished. 相似文献
8.
9.
Hiroyuki Kataoka Kentaro Ehara Rie Yasuhara Keita Saito 《Analytical and bioanalytical chemistry》2013,405(1):331-340
We have developed a simple and sensitive method for the simultaneous determination of testosterone (TES), cortisol (CRT), and dehydroepiandrosterone (DHEA) in saliva by automated online in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a Discovery HS F5 column. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample at a flow rate of 200 μL/min using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. The in-tube SPME LC–MS/MS method showed good linearity with correlation coefficients r?≥?0.9998 for TES, CRT, and DHEA using their respective stable isotope-labeled internal standards. The intra-day and inter-day precisions (relative standard deviations) were below 4.9 and 8.5 % (n?=?5), respectively. This method was successfully utilized to analyze TES, CRT, and DHEA in saliva samples without any other pretreatment or interference peaks, and the quantification limits (S/N?=?10) of TES, CRT and DHEA were about 0.01, 0.03 and 0.29 ng/mL saliva, respectively. The recoveries of these compounds spiked into saliva samples were each above 94 %. This method was applied to analyze changes in salivary TES, CRT, and DHEA levels resulting from stress and fatigue load. 相似文献
10.
Gerui Pei Dr. Pei Zhao Song Xu Xintian Zhao Prof. Chuncai Kong Prof. Zhimao Yang Prof. Masahiro Ehara Prof. Tao Yang 《ChemistryOpen》2020,9(11):1195-1201
The coordination of 10-electron diatomic ligands (BF, CO N2) to iron complexes Fe(CO)2(CNArTripp2)2 [ArTripp2=2,6-(2,4,6-(iso-propyl)3C6H2)2C6H3] have been realized in experiments very recently (Science, 2019 , 363, 1203–1205). Herein, the stability, electronic structures, and bonding properties of (E1E2)Fe-(CO)2(CNArTripp2)2 (E1E2=BF, CO, N2, CN−, NO+) were studied using density functional (DFT) calculations. The ground state of all those molecules is singlet and the calculated geometries are in excellent agreement with the experimental values. The natural bond orbital analysis revealed that Fe is negatively charged while E1 possesses positive charges. By employing the energy decomposition analysis, the bonding nature of the E2E1–Fe(CO)2(CNArTripp2)2 bond was disclosed to be the classic dative bond E2E1→Fe(CO)2(CNArTripp2)2 rather than the electron-sharing double bond. More interestingly, the bonding strength between BF and Fe(CO)2(CNArTripp2)2 is much stronger than that between CO (or N2) and Fe(CO)2(CNArTripp2)2, which is ascribed to the better σ-donation and π back-donations. However, the orbital interactions in CN−→Fe(CO)2(CNArTripp2)2 and NO+→Fe(CO)2(CNArTripp2)2 mainly come from σ-donation and π back-donation, respectively. The different contributions from σ donation and π donation for different ligands can be well explained by using the energy levels of E1E2 and Fe(CO)2(CNArTripp2)2 fragments. 相似文献