首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 281 毫秒
1.
Proofs are given of the structures of two new glycosides of the furostan series isolated from the leaves of the plantNolina microscarpa S. Wats. (family Dracaenaceae). Nolinofuroside D is (25S)-furost-5-ene-1,3,22,26-tetraol 1-O--D-galactopyranoside 26-O--D-glucopyranoside (I), and nolinofuroside F is (25S)-furost-5-ene-1,3,22,26-tetraol 1-O--D-fucopyranoside 26-O--D-glucopyranoside 3-O--L-rhamnopyranoside (VII). The latter was characterized as its 22-O-methyl ether (VIII). Nolinofuroside E (IV) has the structure of (25S)-furost-5-ene-1,3,22,26-tetraol 26-O--glucopyranoside 1-O-[O--L-rhamnopyranosyl-(12)--D-fucopyranoside], which followed from the structure of the fermentation product (VI). The products of the fermentation of the above-named compounds were present in the plant in only trace amounts. Only one of them — nolinospiroside D (III) — has not been described previously. This monoside of the spirostan series is (25S)-spirost-5-ene-1,3-diol 1-O--D-galactopyranoside.M. V. Frunze Simferopol' State University. Institute of Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 678–686, September–October, 1991.  相似文献   

2.
Summary Aqueous suspensions of AgI were studied by the electric birefringence method. The rotatory diffusion constant and the relation between two electric moments of the particles (defined by the ratio ) were determined from the dependence of the electric birefringence on the frequency of the applied field (=229s –1; =2,37). These parameters were also calculated from the electric birefringence data in rapidly reversed electric pulses. The obtained values are=237s –1 and =1,09. The correspondence of the-values is satisfactory. The discrepancy of the -values may be due to the polydispersity of the investigated suspension. The dependence of electric birefringence on the frequency of the applied field, the difference between the initial slopes of the curvesn/E = 2 andn/E ~ 2 and the type of the birefringence at field reversal show that the orientation of the AgI particles is due to the interaction of two electric moments with the applied field, which are directed along the larger dimension of the particles. One of both electric moments is the induced dipole moment connected with the displacement of the ions in the double electric layer. The other moment shows a slow relaxation between 10 Hz and 1 kHz and may be related to either the permanent or a slow induced dipole moment.
Zusammenfassung Es wurden wäßrige AgI-Suspensionen mit Hilfe der elektrischen Doppelbrechung untersucht. Die Rotationsdiffusionskonstante und die Beziehung —definiert als Verhältnis - zwischen zwei elektrischen Momenten der Teilchen wurden aus der Abhängigkeit der elektrischen Doppelbrechung von der Frequenz des angelegten Feldes bestimmt (=229s –1;=2,37). Diese Parameter wurden auch aus Messungen der elektrischen Doppelbrechung im elektrischen Feld mit rechteckförmigen Impulsen wechseln der Polarität berechnet. Die erhaltenen Werte,=237s –1 und =1,09, stimmen im Fall gut, im Fall schlecht überein, was auf die Polydispersität der untersuchten Dispersionen zurückgeführt werden kann. Aus der Abhängigkeit der elektrischen Doppelbrechung von der Frequenz des angelegten Feldes, aus der Differenz zwischen den Anfangssteigungen der Kurvenn/E = 2 undn/E ~ 2 und aus dem Verhalten der Doppelbrechung bei rechteckförmigen Pulsen wechselnder Polarität geht hervor, daß die Orientierung der AgI-Partikel von der Wechselwirkung zweier elektrischer Momente mit dem angelegten elektris chen Feld herrührt, die beide mit der Richtung der längeren Achse der Teilchen übereinstimmen. Eines der beiden Momente ist das induzierte Dipolmoment und kommt durch eine sehr schnelle Platzverschiebung der Ionen in der elektrischen Doppelschicht zustande. Das andere Moment zeigt eine langsame Relaxation im Bereich 10 Hz bis 1 kHz und kann entweder mit dem permanenten Dipolmoment oder mit einem langsamen induzierten Dipolmoment in Zusammenhang gebracht werden.


With 4 figures and 1 table  相似文献   

3.
It has been found that only the cis isomer (liquid) of 2,5-dimethyltetrahydro-4-thiopyranone is cyanoethylated under the usual conditions. 2,5-Dimethyl-5-(-carboxyethyl)tetrahydro-4-thiopyranone was synthesized by the acid hydrolysis of 2,5-dimethyl-5-(-cyanoethyl)-tetrahydro-4-thiopyranone. The selective reduction with aluminum isopropoxide of 2,5-dimethyl-5-(-eyanoethyl) tetrahydro-4-thiopyranone and of the individual isomers of 2,5-dimethyl-5-(-cyanoethyl)-4-piperidone gave the isomeric 2,5-dimethyl-5-(-cyanoethyl)-tetrahydro-4-thiopyranols and -4-piperidols. The reaction of the isomeric 5-cyanoethyl-4-piperidols with allyl bromide gave the corresponding 1-allyl-2,5-dimethyl-5(-cyanoethyl)-4-piperidols.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 12–14, January, 1972.  相似文献   

4.
2-(-Ethoxyvinyl)dioxolanium salts were obtained by reaction of ortho esters with 2,4,4,5,5-pentamethyl-1,3-dioxolanium perchlorate in acetic anhydride. Alkaline hydrolysis of 2-(-ethoxyvinyl)-4,4,5,5-tetramethyl-1,3-dioxolanium perchlorate leads to the corresponding ,-unsaturated aldehyde. Substituted 2-(-aminovinyl)-1,3-dioxolanium perchlorates are formed by reaction of this salt with aromatic amines, amino acids, and urea. These perchlorates readily split out perchloric acid in alkaline media to give Schiff bases. The charges and electron densities were calculated for the 2-(-methoxyvinyl)-1,3-dioxolanium cation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1614–1617, December, 1973.  相似文献   

5.
The effects of -cyclodextrin (-CyD), heptakis(2,6-di-O-methyl)--cyclodextrin (DMCyD) and heptakis(2,3,6-tri-O-methyl)--cyclodextrin (TMCyD) ontrans-cis photoisomerization of 1-ethyl-4-(4-hydroxystyryl)pyridinium (POH) have been studied in aqueous solutions. The ratio of [cis]/[trans] for POH in the photostationary state at pH 8.54 was remarkably reduced by the presence of CyD or DMCyD. The reduction of the [cis]/[trans] ratio in the photostationary state was explained in terms of the shift of the equilibrium of POH + trans PO trans + H toward PO trans formation. The binding constants of CyD and DMCyD for PO trans were 2.00- and 1.36-fold larger than those for POH + trans , respectively. The binding constants of TMCyD for both species are much smaller than those of CyD and DMCyD. This result indicates that PO trans , which has a betain structure, forms stable complexes with CyD and DMCyD with its hydrophobic parts inside and the charged parts outside the CyD cavities.  相似文献   

6.
Some physicochemical and biological properties of a new branched cyclodextrin, 6-O--(4-O--d-glucuronyl)-d-glucosyl--cyclodextrin GUG--CyD) were investigated. Further, theinteraction of GUG--CyD with several drugs was studied by the solubility and spectroscopic methods, and compared with those of parent -CyD and 6-O--maltosyl--CyD(2--CyD).The hemolytic activity of GUG--CyD on rabbit erythrocytes was lower than those of -CyD and 2--CyD. GUG--CyD and 2--CyD showed negligible cytotoxicity on Caco-2 cells up to at least 0.1 M. The inclusion ability of GUG--CyD to neutral and acidic drugs was comparable to or slightly smaller than those of -CyD and 2--CyD, probably because of a steric hindrance of the branched sugar. On the other hand, GUG--CyD showed greater affinity for the basic drugs, compared with -CyD and 2--CyD, owing to the electrostatic interaction of its carboxylate anion with positive charge of basic drugs. Thus GUG--CyD may be useful as a safe solubilizing agent particularly for basic drugs.  相似文献   

7.
Summary Equimolar quantities of CrCl3 · 3THF and-diketones, -dkH, react to yield CrCl2(-dk) · 2THF and CrCl2(-dk) · THF complexes in coordinating and noncoordinating solvents respectively. For 1 : 2 and 1 : 3 molar ratios of reactants, derivatives of general formulae CrCl(-dk)2 and Cr(-dk)3 (where-dkH = acerylacetrrnc, benzoylacetonc and dibenzoylmethane) have been isolated. All complexes have been characterized by elemental analysis, molecular weights and by i.r. spectra.  相似文献   

8.
A new glycoside (cyclofoetoside B) (I) has been isolated from the epigeal part of the plantThalictrum foetidum L. (Ranunculaceae). On the basis of chemical transformations and with the aid of physicochemical characteristics it has been established that cyclofoetoside B is 24S-cycloartane-3, 16, 24, 25, 29-pentaol 3-O--L-arabinopyranoside 16-O-[O--L-rhamnopyranoside-(1 6)--D-glucopyranoside], C47-H80O17, mp 194–197°C (methanol); [] D 24 +15.7 ± 2° (c 0.88; pyridine). The enzymatic hydrolysis of (I) has yielded cyclofoetigenin B (III), 24S-cycloartane-3,16,24,25,29-pentaol 16-O--D-glucopyranoside, (IV), C36H62O10, mp 223–225°C (acetone), [] D 24 +37 ± 2° (c 0.97; methanol) and 24S-cycloartane-3,16,24,25,29-pentaol 16-O-[O--L-rhamnopyranosyl-(1 6)--D-glucopyranoside, C42H72O14, mp 229–231°C (methanol), [] D 30 +41 ± 2° (c 0.7; methanol). Details of the IR and1H and13C NMR spectra of the compounds are given.Irkutsk Institute of Organic Chemistry, Academy of Sciences of the USSR. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Trashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 341–345, May–June, 1986.  相似文献   

9.
Two new steroid glycosides, which have been called echinasterosides B1 and B2 have been isolated from the starfishEchinaster sepositus. Using chemical transformations (methylation, hydrolysis) and also spectral methods (1H and13C NMR spectroscopy and GLC-MS) the complete chemical structure of B1 has been established as 15-acetoxy-5-cholestane-3,4,6,8,24-pentaol 24-O[O-(2)O÷ methyl--D-xylopyranosyl)-(13)--L-arabinofuranoside] (I) and that of glycoside B2 as 5-cholestane-3,4,6,8,15,24-hexaol 24-O-[O÷(2-O-methyl--D-xylopyranosyl)-(13)--L-arabinofuranoside] (II).Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Pirodnykh Soedinenii, No. 2, pp. 246–249, March–April, 1987.  相似文献   

10.
    
A holostane oligoglycoside — pseudostichoposide A — has been isolated from the holothurianPseudostichopus trachus Sluiter, collected on the oceanic side of the island of Urup (Kurile Islands). Its structure has been established with the aid of13C and1H NMR spectroscopy and partial acid hydrolysis with sulfuric acid in the presence of butanol as 3-{O-(3-O-methyl--D-quinovopyransoyl-(1 3)-O--D-xylopyranosyl-(1 4)-O--D-quinovopyranosyl-(1 2)-[4-O-(sodium sulfato)--D-xylopyranosyloxy]}-holost-7-en-22-one. Its native genin, which has been called urupogenin (3-hydroxyholost-7-en-22-one) was obtained on partial hydrolysis in the form of an individual compound. It is a new holostane derivative.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 678–684, September–October, 1989.  相似文献   

11.
    
Summary FromRhodiola algida we have isolated a new -lactone — alginoside (I) with the composition C13H22O8, mp 192°C. It has been shown that it has the structure of-ethyl--(-D-glucopyranosyloxy)--methylbutyrolactone.The aglycone algin obtained by the hydrolysis of (I) is also a new compound, and it has the structure-ethyl--hydroxy--methylbutyrolactone.All-Union Scientific-Research Institute of Medicinal Plants. M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–339, May–June, 1975.  相似文献   

12.
Correlated measurement of the lifetime and of the lineshape of the 511 keV annihilation radiation of positrons (age-momentum correlation, AMOC) has become a powerful tool for investigating reactions of positron or positronium in condensed matter as a function of time. The beam-based + AMOC method installed at the Stuttgart relativistic positron beam facility (E kin e+ 4MeV) offers substantial advantages over the conventional E coincidence technique resulting in a fast data taking due to the unity detection efficiency of the + scintillator which provides the start signal for the lifetime measurement. In this paper the application of AMOC to positronium chemistry is illustrated by the study of spin conversion of positronium in the system methanol/HTEMPO as a function of HTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, a paramagnetic solute) concentration. The same technique can be applied to other systems and other reactions in positronium chemistry, e. g., oxidation or complex formation.  相似文献   

13.
The crystalline isomorphs of-zeolite containing boron or gallium in the framework positions have been synthesized and the products characterized by comparing them with Al- zeolite. Evidence for the presence of B or Ga in the zeolite lattice framework has been confirmed by spectroscopic (XRD, IR and29Si,27Al and11B MASNMR), DTA/TG, ion exchange, sorption and catalytic activity results. Chemical analysis and NMR confirm the absence of any significant amount of Al in the zeolite (SiO2/Al2O3=2000). The XRD pattern of the as-synthesized B- and Ga- compounds matched well with that of Al- zeolite. Lattice B and Ga leads to a change in the X-rayd values. Framework and bridging hydroxyl stretching IR bands of-zeolite are shifted due to incorporation of gallium and boron into the zeolitic framework. MASNMR spectra of11B and29Si also suggest the presence of tetrahedrally coordinated B(III) or Ga(III) ions in the-zeolite framework. B and Ga-zeolites exhibit significant ion exchange capacity and catalytic activity in them-xylene isomerization reaction. The shifts in the IR bands towards higher frequency in B- and lower frequency in Ga-, the observed ion exchange capacities and catalytic properties, indicate the presence of B3+ or Ga3+ ions in the framework of-zeolite.  相似文献   

14.
-Picolinium-p-chlorophenacylide (-PCFY) acts as a retarder for polymerization of N-vinyl pyrrolidone. The polymerization runs were carried out at 60°C using benzene as an inert solvent. The kinetic equation for the present system may be written asR p [-PCPY]–1.0 [AIBN]0.66[N-VP]1.0. The value of overall energy of activation for polymerization in presence and absence of-PCPY was computed as 44.0 and 42.3 kJ mol–1, respectively. The inverse relationship ofR p and¯M v with-PCPY suggests that-PCPY acts as a polymerization retarder. The retarding effect is also evidenced by higher initiator exponent value and higher value of energy of activation in presence of ylide. A mechanism is also proposed in which polymer propagating chain combines with one ylide component to give resonance stabilized radical.  相似文献   

15.
Summary 3-Aroyl-4-aryl-2-pyrazolines (21–40) have been synthesized by the reaction of ,-unsaturated ketones (1–20) with diazomethane. These 2-pyrazolines gave -methyl-,-unsaturated ketones (41–46) on thermal denitrogenation.Dedicated to Prof. Dr.F. Sauter on the occasion of his 65th birthday  相似文献   

16.
Summary From a methanolic extract of the skins of the bulbs ofAllium giganteum Rgl, a new steroid glycoside has been isolated — aginoside, which is (25R)-5-spirostan-2, 3, 6-triol 3-0-{[0--D-xylopyranosyl-(13)-]-[0--D-glucopyranosyl-(12)]-0--D-glucopyranosyl-(14)-0--D-galactopyranoside}.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 480–486, July–August, 1976.  相似文献   

17.
Three new glycosides, D1, D2, and D3, have been isolated from the Far Eastern starfishDistolasterias nipon. They have been identified by chemical and physicochemical methods as 5-cholestane÷3,6,8,15,24-pentaol 3,24-di-O--D-xylopyranoside, t-cholest-22-ene-3,6,8,15,24-pentaol 3,24-di-O--D-xylopyranoside (II), and 5-cholestane-3,6,8,15,24-pentaol 24-O--D-glucopyranoside 3-O--D-xylopyranoside (III).Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 250–255, March–April, 1987.  相似文献   

18.
Conclusions It was shown that the reaction gas chromatography method can be used to determine the rate constants for the cleavage of the Si-C bonds in-trialkylsilylpropionic acids under the influence of sulfuric acid. We determined the rate constants for the cleavage of the Si-C bonds in the -trimethylsilylpropionic and-dimethylbutylsilylpropionic acids under the influence of sulfuric acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 195–197, January, 1974.  相似文献   

19.
Conformational analysis of inclusion complexes of sodium 3-hydroxy-2-naphthalenecarboxylate with -cyclodextrin and heptakis-(2,3,6-tri-o-methyl)--cyclodextrin in D2O was investigated by 1D and 2D 1HNMR measurements. The results show that part of the naphthyl group of sodium 3-hydroxy-2-naphthalenecarboxylate is situated in the 2,3-OH side of the -cyclodextrin cavity asymmetrically while the whole naphthyl group is included in the heptakis-(2,3,6-tri-o-methyl)--cyclodextrin cavity with the caboxylate and hydroxy group close to the 6-OCH3 group.  相似文献   

20.
Conclusions 3-Acetyl--3,4-epoxycarane under the influence of bases is easily rearranged to the,-unsaturated ketol, namely 3-acetyl-4-caren-3-ol, by the E2 mechanism of the-elimination reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2084–2086, September, 1971.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号