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 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.     

New route for the synthesis of 2-thiouracil analogues of 3′-azido-2′,3′-dideoxy nucleosides

Summary Reaction of 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pentofuranoside (5) with silylated 2-thiouracil and 5-alkoxy-2-thiouracils in the presence of trimethylsilyl trifluoromethanesulfonate afforded an anomeric mixture of the corresponding 3-azido-2,3-dideoxy-2-thiouridine derivatives with the -anomer as the main product. Deprotected nucleosides were obtained by treatment with tetrabutylammonium fluoride.

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Ein neuer Weg zur Synthese von 2-Thiouracil-Analogen von 3-Azido-2,3-dideoxy-Nucleosiden

Zusammenfassung Die Reaktion von 3-Azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pentofuranosid (5) mit silyliertem 2-Thiouracil und 5-Alkoxy-2-thiouracil in Gegenwart von Trimethylsilyltrifluormethansulfonat ergab eine anomere Mischung der entsprechenden 3-Azido-2,3-dideoxy-2-thiouridin-Derivate, wobei das -Anomer das Hauptprodukt darstellte. Die ungeschützten Nucleoside wurden mittels Behandlung mit Tetrabutylammoniumfluorid erhalten.

     

Synthesis of 2β, 3β, 14α-trihydroxy-Δ4,7-6-ketosteroids and their derivatives

A scheme using -sitosterol as an example for synthesizing 2, 3, 14-trihydroxy-^4,7-6-ketosteroids and their derivatives from 3-hydroxy-⁵-steroids was developed.Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, 220141, Belarus, Minsk, ul, akad. Kuprevicha, 5/2. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 244–248, May–June, 2000.     

On-Line Inhibited Chemiluminescence Detection of 2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-Glucoside and Baicalin Separated by Capillary Electrophoresis

A capillary electrophoresis on-line inhibited luminol-K₃Fe(CN)₆ chemiluminescence method was employed for the determination of 2,3,5,4-tetrahydroxystilbene-2-O--D-glucoside (I) and baicalin (baicalein 7-O-glucuronide, II). In this system, luminol was added to running buffer solution and introduced at the head of the separation capillary, and K₃Fe(CN)₆ was introduced at the end of the capillary. The parameters affecting the separation process and CL detection were studied. Under the optimum conditions, the baseline separation of the two analytes was obtained within 4min. The detection limits (S/N=3) for I and II were 3.0×10^–6M and 1.2×10^–6M, respectively. This proposed method was successfully applied to the determination of II in traditional Chinese medicines.     

Die Acetalgruppe, 1. Mitt. Acetale von Halogenmethyl-arylcarbinolen

Several halomethyl-arylcarbinols were prepared, and the influence of substituents on enantiomer selectivity in the acetalisation reaction with [2S-(2,3a,4,7,7a)]-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ol was examined.

Unserem sehr verehrten Lehrer, Herrn Prof. Dr.Otto Hromatka, mit den besten Wünschen zum 80. Geburtstag gewidmet.     

Enantiomer separations with chromatographic supports based on β-cyclodextrin polymers immobilized on porous silica. Role of the polymer structure in separating ability

Summary Two -cyclodextrin (-CD)-containing polymers have been prepared either by condensation of -CD molecules with a bifunctional reagent or by grafting a -CD derivative on to a linear polymer (polyvinylimidazole). HPLC stationary phases were obtained by adsorption of the -CD polymers on to silica. The ability of these chromatographic supports to resolve racemic mixtures of organic compounds such as amino acid derivatives, phenylhydantoins, barbiturates, and hydroxycoumarin derivatives has been investigated. Results were found to depend on the chemical structure of the -CD polymers     

Triterpene Glycosides of Zygophyllum eichwaldii. II. Structure of Zygoeichwaloside I

Column chromatography of roots ofZygophyllum eichwaldiiC.A.M. (Zygophyllaceae) afforded the new glycoside zygoeichwaloside I. Acid hydrolysis, alkaline saponification, solvolysis, and ¹ H and ¹³ C NMR spectroscopies using COSY, TOCSY, ROESY, HSQC, and HMBC methods established its structure as the 28-O--D-glucopyranosyl ester of pomolic acid 3-O--D-2-O-sulfonylgalactopyranoside.     

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.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

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.     

α-Alkoxy-β-dicarbonylverbindungen durch Acylierung von Lithiumenolaten

A series of -alkoxy--dicarbonyl compounds2 were prepared by acylation of lithium enolates in good to excellent yields by a simple one-pot procedure.

     

2,2′-Diphenyl-Δ3,3′-bi-3H-indole-1,1′-dioxide: Molecular interactions and crystal structure

The Dinitrone 2,2-diphenyl-^3,3-bi-3H-indole-1,1-dioxide acts as a demethylating and dehydrogenating agent. The mechanism of interaction of the dinitrone with donors and acceptors does not involve intermediate charge-transfer complexes probably due to a self association between dinitrone molecules (as supported by X-ray determinations). The crystal structure of the dinitrone was obtained by direct methods;a=9.967 (2),b=19.817 (3),c=10.875 (2) Å, =111.2 (2)°, space group P2₁/n. The finalR andR _w were 0.089 and 0.063 for all measured reflexes.

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2,2-Diphenyl-^3,3-bi-3H-indol-1,1-dioxid: Molekulare Wechselwirkungen und Kristallstruktur

Zusammenfassung Das Dinitron 2,2-Diphenyl-^3,3-bi-3H-indol-1,1-dioxid wirkt als Demethylierungs- und Oxydationsmittel. Die Wechselwirkung des Dinitrons mit Elektronen-Acceptoren und Elektronen-Donatoren geht wegen der Selbstassoziation zwischen den Dinitron-Molekülen ohne die dazwischenliegende Bildung eines Charge-Transfer-Komplexes vor sich; das wird auch von Röntgenstrukturuntersuchungen gestützt. Die Kristallstruktur wurde mit direkten Methoden ermittelt:a=9.967 (2),b=19.817 (3),c=10.875 (2) Å; =111.2 (2)°. P2₁/n. Die endgültigen WerteR undR _w waren 0.089 und 0.063 für alle gemessenen Reflexe.

     

Charge control in the formation of complexes of phenol with unsaturated compounds containing organometallic substituents from group IV

The resonance donor effect of the , conjugation of R₃M and R₃MCH₂ (M = Si, Ge, Sn; R is an alklyl group) substituents with the triple bond in compounds R₃MC=CX and R₃MCH₂CCX (X = H, R) changes on passing from isolated molecules to their H-complexes. A partial ⁺ charge on the triple bond enhances , conjugation; a partial ^– charge on the triple bond has practically no effect on the resonance properties of R₃M substituents, whereas the , conjugation of R₃MCH₂ substituents diminishes owing to the effect of negative direct resonance interaction. The effect of , conjugation on the effective negative charges of the carbon atoms in the -CC- fragments was estimated quantitatively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1041–1046, June, 1994.This work was supported by the Russian Fundation for Basic Research (Grant 93-03-18372).     

Hexafluoroacetone as Protecting and Activating Reagent. Glycosylated Malic, Citramalic, and Thiomalic Acid Derivatives, New Glycosylated Building Blocks for Drug Design [1]

Summary. Glycosylated -hydroxy and -mercapto acids have been synthesized starting from malic/citramalic/thiomalic acid and Ac₄--D-Glc-NH₂/Bzl₄--D-Glc-NH₂ using hexafluoroacetone as protecting and activating reagent.Dedicated to Prof. Dr. Horst Wilde on the occasion of his 65^th birthday     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.     

Stereochemistry of planarchiral compounds,part XIII: Crystal structure of Meso-10,10′-dibromo-2,2′-bi-(1,6-methano-[10]-annulenyl)

Summary Crystallization of the mesoform of the title compound1 from benzene-pentane in the presence of 5% of (+)(R) _p (S) _a (R) _p -1 afforded crystals, the structure of which was determined in the achiral spacegroup P2₁/a-C _2h ⁵ . The configuration (R) _p (S) _p was confirmed, the torsional angle around the 2,2-bond is 68.6° and 72.1° (C3-C2-C2-C3 and C1-C2-C2-C1, resp.). The twist of the best planes through the perimeter carbonatoms 3, 4, 5 and 7, 8, 9 (3, 4, etc., resp.) is 26.0° and 19.8°. The colours of the crystals of the stereoisomers of1 depend on the torsional angles and thereby on the conjugation of the -systems. Meso, monoclinic (70.3°): light yellow; racemate, opt. inactive (56.2°): yellow; enantiomer of the racemate (34.4°): orange (average -values).

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Stereochemie planarchiraler Verbindungen, 13. Mitt.: Die Kristallstruktur von Meso-10,10-dibrom-2,2-bi-(1,6-methano-[10]-annulenyl)

Zusammenfassung Kristallisation der Meso-Form der Titelverbindung1 aus Benzol-Pentan in Gegenwart von 5% (+)(R) _p (S) _a (R) _p -1 lieferte Kristalle, deren Struktur in der achiralen Raumgruppe P2₁/a-C _2h ⁵ bestimmt werden konnte: Die Konfiguration (R) _p (S) _p wurde bestätigt, der Torsionswinkel um die 2,2-Bindung beträgt 68.6 bzw. 72.1° (C3-C2-C2-C3 bzw. C1-C2-C2-C1). Die Verkippung der besten Ebenen, definiert durch die Perimeter-C-Atome 3, 4, 5 und 7, 8, 9 (bzw. 3, 4, etc.) beträgt 26.0 bzw. 19.8°. Die Farben der Kristalle der Stereoisomere von1 hängen von den Torsionswinkeln und damit von der Konjugation der -Systeme ab: Meso, monoklin (70.3°): hellgelb; Racemat, opt. inaktiv (56.2°): gelb: Enantiomer des Racemates (34.4°): orange (gemittelte Werte).

     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.     

Convergent synthesis of 2′,3′-dideoxy-3′-mercapto nucleosides — Potential anti-HIV agents

Summary Methyl 3-benzoylthio-5-O-tert-butyldiphenylsilyl-2,3-dideoxy--D-erythro-pentofuranoside (4) and its corresponding anomer5 were synthesized in four steps from 2-deoxy-D-ribose and used as substrates for the synthesis of nucleosides by condensation with silylated thymidine and N⁶-isobutyryladenine. The nucleosides were deprotected by treatment with Bu₄NF inTHF followed by reaction with MeONa in MeOH to give 3-deoxy-3-mercaptothymidine (8), 2,3-dideoxy-3-mercaptoadenosine (15) and its corresponding anomer16. In the latter reactions it was important to use degassed solvents to minimize formation of the corresponding disulfides of purine nucleosides. Using Bu₄NF, without subsequent reaction with MeONa in the deprotection reaction, resulted in intermolecular transesterification reactions.On leave from Chemistry Department, Faculties of Science and Education, Tanta University, Tanta, Egypt     

Enhanced dissolution and oral bioavailability of α-tocopheryl esters by dimethyl-β-cyclodextrin complexation

Inclusion complexation of heptakis (2,6-di-O-methyl)--cyclodextrin (DM--CyD) with -tocopheryl acetate and -tocopheryl nicotinate in aqueous solution was studied by the solubility method. The aqueous solubilities of the esters were about 10⁵ times increased by DM--CyD complexation. The phase-solubility diagram of the tocopheryl ester-DM--CyD systems showed a typicalA _p type, and the stability constants (K) of high-order complexes were estimated by analyzing the upward curvature of the diagrams. The solid complex of -tocopheryl nicotinate with DM--CyD in a molar ratio of 12 was prepared by the kneading method. The dissolution rate of the solid complex was much greater than that of the drug itself, and the rapidly dissolving form of -tocopheryl nicotinate, as an example, showed a markedly increased bioavailability (about 70-fold) after oral administration to fasted dogs.