Triterpene Glycosides of Zygophyllum eichwaldii. III. Structure of Zygoeichwaloside G

The new triterpene glycoside zygoeichwaloside G was isolated from the roots of Zygophyllum eichwaldii C.A.M. by column chromatography. Acid hydrolysis and PMR and ¹³C NMR spectroscopy using twodimensional COSY, TOCSY, and HSQC and analysis of HMBC and ROESY spectra established that glycoside G is 19--hydroxyursolic acid 3-O--L-(2-O-sulfo)-arabinopyranoside.     

Triterpene Glycosides from Plants of the Astragalus Genus. III. Structure of Cyclounifolioside C from Astragalus unifoliolatus

The known compound cyclocantogenin (1) and a new cycloartane glycoside cyclounifolioside C (2), which has the structure 24R-cycloartan-3,6,16,24,25-pentaol 3-O--D-glucopyranoside, were isolated from roots of Astragalus unifoliolatus Bunge. The structures of the isolated compounds are established using hydrolysis and spectral data.     

Triterpene Glycosides from Plants of the Astragalus Genus. Structure of Cyclounifolioside A from Astragalus unifoliolatus

The known compound oleanolic acid (1) and a new cycloartane glycoside cyclounifolioside A (2), which has the structure 6,16-di-O-acetyl-24R-cycloartan-6,16,24,25-pentaol 3-O--D-glucopyranoside, were isolated from Astragalus unifoliolatus Bunge. The structures of the isolated compounds were established using chemical transformations and two-dimensional spectra (TOCSY, ROESY, HMBC, HSQC, COSY).     

Triterpene glycosides ofFatsia japonica. I. Isolation and structure of glycosides fromFatsia japonica seeds

The known triterpene glycosides hederagenin 3-O--L-arabinopyranoside, hederagenin 3-O-\-D-glucopyranoside, oleanolic acid 3-O--sophoroside, hederagenin 3-O--sophoroside, and their 28-O--gentiobiosyl esters, respectively, in addition to the new triterpene glycoside 3-O--sophorosyl-28-O--L-rhamnopyranosyl-(14)-O--gentiobiosyl hederagenin are isolated fromFatsia japonica (Araliaceae) seeds. The structures of these glycosides are established using chemical and spectral methods.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 131–133, March–April, 2000.     

Triterpene Glycosides of Astragalus and Their Genins. LXI. Occurrence of Cycloartane 6-O-Monodesmosides

Cyclosiversigenin 6-O--L-rhamnopyranoside and 6-O--D-glucopyranoside were isolated fromAstragalus coluteocarpusBoiss. (Leguminosae) andAstragalus dissectusB. Fedtsch. et N. Ivanova, respectively. Cyclosiversigenin 5-O--L-rhamnopyranoside was shown to be an artifact forAstragalus coluteocarpus.Thus, the cyclosiversigenin 6-O--D-glucopyranoside that was isolated from certainAstragalusspecies is hypothesized also to be an artifact. Glycosylation of the 6 -hydroxyl group of cycloartanes by D-glucose and D-xylose, in contrast with other substituents, does not change the low-field position of the PMR signal of the 4-CH ₃ group (1.65 2.01 ppm) that is caused by the influence of deuteropyridine directly on the 6 -hydroxyl. Obviously one of the hydroxyls of the -D-glucopyranoside or -D-xylopyranoside residues has the same effect in this instance.     

Triterpene glycosides ofScheffleropsis angkae. I. Structure of glycosides L-B1, L-B2, L-H1, and L-H2

The structures of four triterpene glycosides from the leaves ofScheffleropsis angkae (Araliaceae) are found by chemical methods and NMR spectroscopy to be the 3-O--L-arabinopyranosides of oleanic and ursolic acids and their 28-O--L-rhamnopyranosyl-(14)-O--gentiobiosyl esters, which are designated L-B₁, L-B₂, L-H₁, and L-H₂, respectively. The glycoside L-H₂ is new.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 136–138, March–April, 2000.     

Triterpene glycosides ofScheffleropsis angkae. II. Structure of glycosides L-E1, L-E2, L-K1, and L-K2

The structures of four triterpene glycosides from leaves ofScheffleropsis angkae (Araliaceae) are established using chemical and NMR methods. The structures 3-O--D-glucopyranosyl-(1-3)-O--L-arabinopyranosides of oleanic and ursolic acids and their 28-O--L-rhamnopyranosyl-(1-4)-O--gentiobiosyl ethers are proposed for L-E₁, L-E₂, L-K₁, and L-K₂, respectively. L-K₁ and L-K₂ are new triterpene glycosides.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 239–241, May–June, 2000.     

Structure and properties of non-classical polymers II. Band structure and spin densities

Theoretical investigation of the band structure of three types of nonclassical polymers, namely alternant (one- and two-dimensional), nonalternant and heteroatomic, are carried out. Although polyradicals, these polymers have a considerable delocalization energy which may determine their relative stability.The spin-density distribution of the alternant type of non-classical polymers corresponds to a ferrimagnetic ground state at 0 K.The non-classical polymers represent a new class of organic systems as their band structure and magnetic properties essentially differ from those of common polymers.     

Photochemical addition of diethyl ether to β,β,β',β'-tetrakis(trifluoromethyl)divinyl ether

The 1:1 adducts of diethyl and ,,','-tetrakis(trifluoromethyl)divinyl ether (1),i.e., 3,5-(ee)-bis[2,2,2-trifluoro-1-(trifluoromethyl)ethyl]-2,6-dimethyl-1,4-dioxane (2) (3 isomers) and 4-ethoxy-1,1,1-trifluoro-2-trifluoromethyl-3-[3,3,3-trifluoro-2(trifluoromethyl)propenyloxy]pentane (3), have been obtained by UV-irradiation of a solution of divinyl ether1 in diethyl ether. The X-ray structural investigation of the all-(e)-isomer of dioxane (2) has been carried out.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 85–88, January, 1994.     

Chemical Composition of Certain Sedum Species of Kazakhstan

The chemical composition of sevenSedumspecies growing in Kazakhstan was studied by chromatography. The contents of seven groups of natural compounds were determined. Comparison with markers and literature data identified 24 compounds including 9 that have not been described previously inSedumspecies     

Interaction of fluoroalkyl-containing β-diketones with amines

The composition of products of the interaction of asymmetric fluoroalkyl-containing -diketones with amines was studied. Mixtures of regioisomeric -aminovinylketones and products of cleavage and secondary condensation are formed, depending on the temperature, the solvent, the nature of the fluorinated and nonfluorinated substituents in the -diketone, and the basicity of the amine. The major product is a -aminovinylketone in which the NH₂ group is removed from the fluoroalkyl substituent. No -aminovinylimines, products of condensation involving two electrophilic centers, were observed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2278–2284, September, 1996.     

Effect of Cyclodextrins on the Chemical Stability of ST1435, a Contraceptive Steroid Progestin, in Aqueous Solution

The influence of cyclodextrins (CDs) on the chemical stability of the contraceptive steroid progestin, ST1435, in aqueous solution has been studied using reversed phase high performance liquid chromatography. The effects of CD structure, temperature, and CD concentration on the rate of degradation were investigated. It was found that the drug degraded to different extents following a pseudo-first order reaction mechanism. The presence of the host molecules affected the degradation rate as a result of complexation which might result in protection of the labile moiety of the drug molecule against degradation. Hydroxypropyl--cyclodextrin (HP--CD) and hydroxyethyl--cyclodextrin (HE--CD) retarded the degradation in contrast to -cyclodextrin (-CD) which accelerated the steroid degradation. The stabilizing action of HP--CD is larger than that of HE--CD. The degradation rate increased upon increasing temperature and the Arrhenius equation is valid. Lineweaver-Burk equation analysis indicated that the steroid included inside the CD cavity degraded three times more slowly than did the free ST1435 in solution. This equation further supported the formation of a 1 : 1 inclusion complex between ST1435 and HP--CD with a stability constant of 934.5 M-1 at 65°C.     

Stereocontrolled synthesis of low-molecular-weight β-O-glycosides from products of decyclization of acylated oligosaccharide glycals

Low-molecular-weight -O-glycosides with aliphatic polyfunctional aglycones were synthesized by Horner-Emmons olefination of O-glycosylated ,-unsaturated aldehydes prepared by acid opening of the dihydropyran ring in totally acylated lactal, cellobial, and gentiobial.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1176–1181, May, 1992.     

Conformational Heterogeneity of a Tripeptide in the Solid State and in Solution: Characterization of a γ-Turn Containing Incipient Hairpin in Solution

A terminally blocked tripeptide Boc--Ala-Aib--Ala-OMe 1 with noncoded amino acids forms a novel type of hairpin structure containing a -turn instead of a conventional -turn in the central loop region in solution. This new type structural motif was characterized by NMR and restraint molecular dynamics simulation study. In the solid state peptide 1 adopts an extended backbone conformation and self-assembles to form supramolecular -sheet.     

Synthesis and sorption properties of new hybrid chelating sorbents with β-alanine functional groups

A series of -aminopropylsilylated sorbents was obtained from different oxide supports (silica gels, silica fillers, macroporous glasses, alumina) and by the direct synthesis (hydrolytic polycondensation of tetraalkoxysilanes with -aminopropyltriethoxysilane). The highest degree of immobilization was achieved for silicas, while the most convenient solvent was methanol. Sorbents with -alanine functional groups were obtained by the subsequent reaction with acrylic acid. The degree of -carboxyethylation was 1.3–1.9, and the highest content of functional groups (v_COOH = 3.23 mmol g^–1) was achieved for carboxyethylated xero gel synthesized by the copolycondensation of tetraethoxysilane with -aminopropyltriethoxysilane. The sorbents containing -alanine possess a higher selectivity of Cu²⁺ ion sorption than the initial -aminopropylsilylated sorbents.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2620–2625, December, 2004.     

Determination of the equilibrium melting point of the β-form of polypropylene

The melting behavior of the -form of isotactic polypropylene (-iPP) was investigated as a function of crystallization time and temperature. Calcium suberate, a selective -nucleating agent was used to produce samples that consist entirely of -form i-PP. The experimental melting points were recorded at different crystallization times and were extrapolated to the start of the crystallization process in order to eliminate the effect of lamellar thickening. Using the non-linear Hoffman—Weeks approach to correlate these extrapolated experimental melting temperatures with the corresponding crystallization temperatures, an equilibrium melting point of 209°C was obtained for -iPP. The equilibrium melting point estimated through the non-linear Hoffman—Weeks analysis is about 30°C higher than that (T _m ⁰=177°C) obtained on the basis of the linear extrapolation. These results are consistent with earlier claims that a linear extrapolation of T _m–T _c data leads to an underestimation of the equilibrium melting point. The results obtained for -iPP exemplify the importance of accounting for both the isothermal lamellar thickening effects and the non-linearity in the T _m–T _c correlation, when the determination of an equilibrium melting point is carried out using a procedure based on the predictions of the Lauritzen—Hoffman secondary nucleation theory.This revised version was published online in November 2005 with corrections to the Cover Date.     

Reaction of β-Cyclodextrin with N-2,3-Epoxypropylphthalimide. Preparation, Characterisation and Study of a New Substituted Cycloheptaamylose. Effects on the Water Solubility of Drugs

The reaction of -cyclodextrinwith N-2,3-epoxypropylphthalimide yielded a set of newamorphous host compounds with high solubility whichwas transmitted to the corresponding host-guestcomplexes. The structure was determined by comparing the 1H- and 13C-NMR spectra with those of theparent compound, the degree of substitution by integration of the corresponding NMR signals, and C, H,and N elemental analysis.     

Synthesis, Properties, and Crystal and Molecular Structures of New Ni(II) Complexes with Sterically Hindered Methoxy-β-iminoketones

This paper describes a procedure for the synthesis of two new volatile complexes, C₂₂H₄₀N₂NiO₄ and C₂₀H₃₆N₂NiO₄, based on sterically hindered methoxy--iminoketones. The compounds were investigated by IR spectroscopy and DTA. Full crystal-chemical analysis has been carried out. The structures are molecular. The complexes have close geometrical characteristics; the distances are Ni–O 1.826 and Ni–N 1.842 ; the O–Ni–N chelate angle is 93.2°. The complexes have an intramolecular hydrogen bond N–H...O, estimated at 2.54 (2.08) . In both structures, the packing of complexes is similar to that in nickel(II) dipivalylmethanate.     

Influence of cyclodextrins on nitrosation of drugs

The World Health Organization issued a nitrosation procedure (NAP Test) which allows to carry out nitrosation under standard conditions. It has proved that the in vitro reaction rates of the fast nitrosatable drugs piperazine, cimetidine and ethambutol are not influenced by -, - and -cyclodextrin. On the contrary, -, -cyclodextrin and heptakis-2,6-di-O-methyl--cyclodextrin enhance the nitrosation of the slower nitrosatable 1-ephedrine and fencamfamine significantly. This possible reaction must be considered if nitrosatable drugs are formulated with cyclodextrins to be administered to human beings.     

Simultaneous determination of tetrahydro-β-carbolines and β-carbolines

Summary Reversed-phase ion-pair HPLC with fluorimetric detectors connected in series was studied for the simultaneous determination of two tetrahydro--carbolines and two -carbolines. After additon of internal standards the samples were reacted with fluorescamine, and then subjected to serial extractions to remove their precursor (tryptamine) from the analytical system. This treatment not only suppressed the artefactual formation of tetrahydro--carbolines and -carbolines during analysis, but also effectively purified them. Under optimum conditions, using trifluoroacetic acid as counter ion, all analytes were separated within 14 min and without major interfering peaks. The quantitative ranges were 0.25–80.0 ng mL^–1 for both tetrahydro--carbolines and 0.1–30.0 ng mL^–1 for both -carbolines. Replicate spiking experiments showed that recovery from most of the samples tested was over 90% and the relative standard deviation ranged from 0.7 to 10.4% within and between assays. The proposed method was applicable to various materials such as soy sauce, vinegar, ketchup, tabasco, beer, wine, sake, whisky, brandy, cows' milk, coffee, cocoa, cheese, cigarette smoke and urine.