共查询到20条相似文献,搜索用时 15 毫秒
1.
Maria Rodríguez Alfonso Gómez Fernando González Eduardo Barzana Agustin López-Munguía 《Applied biochemistry and biotechnology》1996,59(2):167-175
Enzyme synthesis of methyl fructoside was studied usingΒ-fructofuranosidase fromSacharomyces cerevisiae and sucrose and methanol as substrates. Taking into account the inhibition and deactivation effects of methanol on the enzyme,
a system with 4.9M (20%, v/v) methanol was selected. At this alcohol level, 35% of sucrose is converted to fructoside at low
or high substrate concentrations. The effect of enzyme concentration, pH, and temperature on both the synthesis and the hydrolysis
of the fructoside was investigated. It was found that if the reaction proceeds at pH 6.0, 4‡C and/or 0.014 mg/mL (3 U/mL)
of Β-fructofuranosidase at varying sucrose concentrations, methyl fructoside may be obtained with a minimum loss of the fructoside
at the end of the reaction. 相似文献
2.
E. G. Mkrtchyan D. S. Yachevskii D. L. Chizhov V. N. Charushin 《Russian Chemical Bulletin》2005,54(9):2150-2156
Reactions of perfluoroalkyl-containing aliphatic 1,3-diketones with triethyl orthoformate afforded a number of β-ethoxy enones.
Their reactions with o-phenylenediamine gave novel perfluoroalkyl-containing tridentate β-amino enones and tetradentate bis(β-amino enones) in high
yields.
Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2086–2092, September, 2005. 相似文献
3.
B. B. Semenov K. A. Novikov V. V. Kachala V. N. Azev 《Chemistry of Natural Compounds》2006,42(5):582-584
The Pictet-Spengler reaction involving β-phenyltryptamine was shown to be diastereo-specific with formation primarily of the (1S*,4R*) diastereomer of 4-phenyl-1-(2-thienyl)-2,3,4,9-tetrahydro-1H-β-carboline, a compound with potential GABA-receptor activity.
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Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 468–470, September–October, 2006. 相似文献
4.
Jun-hua Shi Yuxun Zhou Ming-lei He Jian Jin Yi-chuan Xiao Jun-hua Xiao Dong-zhi Wei 《Chemistry of Natural Compounds》2006,42(3):325-327
A novel compound, biotinylated 18β-glycyrrhetinic acid (BGA), was synthesized. It is a compound of 18β-glycyrrhetinic acid linked with biotin.
Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 266–267, May–June, 2006.
An erratum to this article is available at . 相似文献
5.
V. A. Tartakovsky A. S. Ermakov D. B. Vinogradov N. V. Sigai 《Russian Chemical Bulletin》1997,46(5):1024-1025
β-Nitroxyalkylnitramines were obtained by nitration of β-hydroxyalkyl sulfamates, products of the condensation of derivatives
of sulfamic acid with alkene oxides, by a mixture of HNO3 and H2SO4.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1061–1062, May, 1997. 相似文献
6.
Hui-Ling Ma Jin-Yi Qin Lei Wang Sheng-Xiang Yang Ming-Hua Chiu Xian-Min Zhang Jin-Ming Gao 《Chemistry of Natural Compounds》2008,44(1):44-47
A new triterpene, taraxast-20(30)-en-3β,12β-diol (1), and eight known compounds were isolated from the leaves of Craibiodendron yunnanense. Their structures were established on the basis of spectral evidence.
Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 35–37, January–February, 2008. 相似文献
7.
The macroscopic solvent effect on static nonlinear polarizabilities of a number of intramolecular charge-transfer (ICT) molecules
have been studied by using the self-consistent-reaction field (SCRF) model in the framework of ab initio time-dependent-HF
(TDHF) method using 3-21G basis set. The two-state model of static β and <γ> have been used to obtain their functional dependence on the ground-state hardness parameter, dipole moment and solvation
energy. The methyl substituted 4-quinopyran and other zwitterionic molecules are found to exhibit strong diminution of both
quadratic and cubic polarizabilities at higher solvent reaction field due to negative solvatochromic effect. However, molecules
showing positive solvatochromism lead to strong enhancement of the NLO response on increase in solvent polarity. The evolution
pattern of the solvent modulated static β and <γ> of 4-quinopyran (4QP) obtained for varying inter-ring torsion angle differ strikingly from that shown by p-amino p'-nitro biphenyl (ANB). 相似文献
8.
The needle oils of Pinus sylvestris L. were analyzed by GC and GC-MS. The results showed some qualitative and quantitative variations. Forty-three components
were identified in the oils of P. sylvestris. All the samples of essential oils contained α-pinene, camphene, and β-pinene as major constituents. Chemical variations
of P. sylvestris samples were discussed.
Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 22–25, January–February, 2006. 相似文献
9.
Xiaodong Jia Xingzeng Zhao Ming Wang Yu Chen Yunfa Dong Xu Feng 《Chemistry of Natural Compounds》2008,44(6):692-695
Two new coumarin biosides, tert-O-β-D-apiofuranosyl-(1→6)-O-β-D-glucopyranosyl-byakangelicin (1) and 2′-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranosyl-peucedanol (2), were isolated from the fresh roots of Angelica dahurica. The structures of the new compounds were elucidated on the basis of spectral analysis.
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 561–563, November–December, 2008. 相似文献
10.
Summary. Arylimines of 2-acetylthiophene and 2-, 3-, and 4-acetylpyridines react with ketenes yielding 4-heterosubstituted β-lactams.
Reactions of imines with ketenes were proved to be diastereoselective. The stereochemistry of the products was confirmed by
X-ray analysis. β-Lactams treated with Lawesson’s reagent gave β-thiolactams. 相似文献
11.
V. S. Renzik V. D. Akamsin I. V. Galyametdinova S. G. Fattakhov B. E. Ivanov 《Russian Chemical Bulletin》1999,48(5):979-983
Dialkyl β-(2-aroxyethylamino)ethylphosphonates,N-[β-(2-methoxyphenoxy)ethyl]-N′-[β-(diethoxyphosphoryl)ethyl]-α,ω-diaminoalkanes, and diethyl β-(N-arylpiperazino)ethyl-phosphonates were synthesized by the reactions of dialkyl vinylphosphonates with β-aroxyethylamines,N-[β-(2-methoxyphenoxy)ethyl]-α,ω-diaminoalkanes, andN-aryl-piperazines, respectively. The compounds synthesized exhibit hypotensive and α-adrenolytic activities.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 987–991, May 1999. 相似文献
12.
Haruko Ikeuchi Kaoru Naganuma Marie Ichikawa Hiromichi Ozawa Tomoya Ino Makoto Sato Hiroko Yonezawa Sonomi Mukaida Akihiro Yamamoto Takeshi Hashimoto 《Journal of solution chemistry》2007,36(10):1243-1259
The diffusion coefficients of several tris(β-diketonato) ruthenium complexes in acetonitrile solutions containing a supporting electrolyte were determined by chronoamperometry.
The diffusion coefficients of the charged complexes, which were produced by electrochemical oxidation or reduction, were also
determined by double potential step chronoamperometry. Two kinds of radii of the complexes were evaluated. One was the Van
der Waals radius and the other was the geometric distance from the center of the complex to the outer surface of the farthest
atom. The latter quantity was determined from X-ray diffractometric data. The diffusion coefficients of the neutral complexes
were discussed on the basis of the Stokes-Einstein equation. Those of charged complexes could not be explained by the theoretical
equation presented by Hubbard and Onsager. 相似文献
13.
A. Amini V. Barclay T. Rundlöf S. Jönsson A. Karlsson T. Arvidsson 《Chromatographia》2006,63(3-4):143-148
This paper reports the determination of caffeine, ephedrine and pseudo-ephedrine in a dietary product by two rapid and simple
methods utilising capillary electrophoresis (CE). The solutes were extracted from the product using 0.2 M HCl and determined
by CE with background electrolytes containing 7.5% highly sulfated-β-cyclodextrin (7–11 sulfate groups per β-CD molecule) at pH 2.5 and pH 7.6. Determination of ephedrine and pseudo-ephedrine was accomplished at pH 2.5 with the anode
at the detection side of the capillary whereas caffeine was quantified at pH 7.6 with a normal electrophoresis polarity mode.
Triethanolamine was added to the running buffer at pH 2.5 in order to reverse the electroosmotic flow (EOF) and thereby speed
up the separation of ephedrine and pseudo-ephedrine.
Revised: 18 November 2005 and 2 January 2006 相似文献
14.
The synthesis of α-amino-β-keto-esters (β-oxo dipeptides) was studied. Corresponding α-amino-β-ketoesters were prepared from BOC-(L)-Valine and BOC-(L)-isoleucine by coupling with (D,L)-threonine hydrochloride and oxidation
with Dess-Martin periodinane (DMP) with a total yield of 48% and 38%, respectively.
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Translated from Chemistry Online, 2007, 70(10): 793–796 [译自: 化学通报] 相似文献
15.
M. I. Merlani L. Sh. Amiranashvili N. I. Men’shova E. P. Kemertelidze 《Chemistry of Natural Compounds》2007,43(1):97-99
5α-Androstan-3β,17β-diol (3b-adiol), a known inhibitor of prostate cancer cell growth, was synthesized from tigogenin. Its structure was confirmed
by NMR and IR spectroscopy and mass spectroscopy.
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Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 81–82, January–February, 2007. 相似文献
16.
Ab initio calculations of the molecules of CH3- and CF3-substituted β-propiothiolactones and the productsof their deprotonation were carried out by the restricted Hartree—Fock method
with full geometry optimization using the 6–31 G* basis set. Peculiarities of the geometry and electronic structure of the systems in question were established. Only 2-methyl-β-propiothiolactone
forms a mesomeric stabilized carbanion in the case of proton abstraction from the α-position of thiolactone cycle. Carbanions
of 3-methyl, 2-, and 3-thrifluoromethyl-β-propiothiolactones are stabilized due to the ring opening to form ketene thiolate
ions. The CH-acidity of fluorine-containing β-thiolactones is much higher than that of nonfluorinated analogs (the differences
in the deprotonation energies are 13.4 to 25.2 kcal mol−1).
Deceased.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1719–1725, September, 1998. 相似文献
17.
Li-juan Yang Xiao-dong Yang Shu Yang Jing-feng Zhao Hong-bin Zhang Liang Li 《Chemistry of Natural Compounds》2006,42(6):649-651
Two new benzoyl esters of glucose 1-O-(E)-4′-methoxybenzoyl-β-D-glucopyranose (1) and 1-O-(E)-4′-methoxybenzoyl-β-D-gluconic acid (2) were isolated from Lagotis yunnanensis, together with six previously known iridoid glucosides. The structures of these compounds were elucidated on the basis of
spectral analysis, including 2D NMR spectroscopy.
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 529–530, November–December, 2006. 相似文献
18.
Salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides, RCH(OH)CH2N(O)=NO− M+ (R=Me, Pri, or But; and M=Li, Na, K, Ag, NH4, or Me4N), were prepared. Their alkylation with alkyl halides R′X (X=Cl, Br, or I) and dimethyl sulfate was studied. Generally, alkylation
afforded mixtures ofN-(β-hydroxyalkyl)-N′-alkoxydiazeneN-oxides RCH(OH)CH2N(O)=NOR′ andO-alkyl-N-(β-hydroxyalkyl)-N-nitrosohydroxylamines RCH(OH)CH2N(NO)OR′.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1996–2001, October, 1998. 相似文献
19.
Summary The electrostatic forces within the active site of theβ-lactamaseStaphylococcus aureus PC1 have been used to predict structures for the precatalytic complex with ampicillin, methicillin, clavulanate and imipenem.
There are significant differences in the orientation of theseβ-lactams within the binding site, which explains the differences in their resistance to the lactamase. The electrostatic forces
were calculated using a distributed multipole analysis ofab initio wave functions for both the lactams and the binding site residues, to ensure a good representation of the orientation dependence
of this dominant contribution. The predicted binding orientations are contrasted with those predicted by overlaying the electrostatic
extrema around the ligands. The accuracy of the ligand-only-based predictions is limited in some cases because of the subtle
steric requirements of the lactamase binding site. 相似文献
20.
A new compound of formula C28H48O with mp 179-180°C (aqueous ethanol) that was called eucanbin was isolated pure by column chromatography of the ethanol extract
of the aerial part of Eupatorium cannabinum L. The structure 24α-methylcholest-20(21)-en-3β-ol was assigned based on chemical and spectral data.
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 318–320, May–June, 2009. 相似文献