Culcitoside C1 from the starfishCulcita novaeguineae andLinckia guildingi

By repeated chromatography on Polikhrom-1, silica gel, and Florisil, ethanolic extracts of two species of starfish,Culcita novaeguineae andLinckia guildingi, have yielded the new steroid glycoside culcitoside C₁ (I): 5-cholestan-3,4,6,8,15,24-hexaol 24-O-[2,4-di-O-methyl--D-xylopyranosyl-(12)--L-arabinofuranoside], C₃₉H₆₈O₁₄, mp 245–248°C, []_D -35.8°, c 0.6; methanol). Its structure was shown by the results of acid hydrolysis, acetylation and methylation, and¹H and¹³C NMR spectroscopy.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 801–804, November–December, 1985.     

Triterpene Glycosides of Tragacantha Stipulosa and Their Genins. Structures of Askendosides G and D and Cycloglobiceposide B from One- and Two-Dimensional 1H and 13C NMR Spectroscopy

Roots of Tragacantha stipulosa Boriss yielded three triterpene glycosides of the cycloartane series: askendoside G (1), askendoside D (2), and cycloglobiceposide B (3). Glycoside 1 is 3-O--L-arabinopyranosyl-(12)--D-xylopyranoside; 16-O--D-glucopyranoside-24R-cycloartan-3,6,16,24,25-pentaol; 2 - 3-O--L-arabinopyranosyl-(12)--D-xylopyranoside; 6-O--D-xylopyranoside-20R,24S-epoxycycloartan-3,6,16,25-tetraol; 3 - 3-O--D-xylopyranoside; 16-O--D-glucopyranoside; 25-O--D-glucopyranoside-24R-cycloartan-3,6,16,24,25-pentaol.     

Phase equilibria in the Ag4SSe-SnTe system

The phase diagram of the system Ag₄SSe-SnTe is studied by means of X-ray diffraction, differential thermal and metallographic analyses and measurements of the microhardness and the density of the material. This diagram is divided into two eutectic-type subdiagrams by the composition Ag₄SSe·2SnTe. The unit-cell parameters of the intermediate phases 3Ag₄SSe·SnTe (phase A) and -Ag₄SSe·2SnTe (phase B) are determined as follows: for phase A: a=0.7851 nm, b=0.7196 nm, c=0.6296 nm, =101.32°, =85.90°, =111.36°; for phase B: a=0.3662 nm, b=0.3303 nm, c=0.3343 nm, =90.74°, =108.94°, =91.91°. The phase Ag4SSe·2SnTe melts congruently at 615°C and a polymorphic transition of the phase takes place at T _- =110°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

On the ternary B 2-phase in the Al-Co-Ga system

Summary Lattice parameter values were determined for the ternary B 2-phase in the Al-Co-Ga system, and it was found that a continuous solid solution exists between -AlCo and -CoGa. Phase boundaries of the ternary phase at 1 100 K were derived from the variation of the lattice parameter with composition.

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Über die ternäre B 2-Phase im System Al-Co-Ga

Zusammenfassung Im Bereich der ternären B 2-Phase im System Al-Co-Ga wurden die Werte des Gitterparameters bestimmt; es stellte sich heraus, daß eine durchgehende feste Lösung zwischen -AlCo und -CoGa besteht. Die Phasengrenzen der ternären Phase bei 1 100 K wurden aus der Änderung des Gitterparameters mit der Zusammensetzung abgeleitet.

     

Triterpene glycosides ofHedera canariensis IV. Structures of glycosides L-F3, L-G0, and L-Gla from the leaves of Algerian ivy

Three minor partially acetylated glycosides have been isolated from the leaves of Algerian ivy, Hedera canariensis Willd. (Araliaceae) — the previously known {3-O-[-L-rhamnopyranosyl-(12)-O--L-arabinopyranoside] 28-O-[-L-rhamnopyranosyl-(14)-O-(6-acetyl--D-glucopyranosyl)-(16)-O--D-glucopyranoside}s of oleanolic acid and of hederagenin (ciwujianoside C₄ and kizuta saponin K₁₁) and the new 3-O-[-L-rhamnopyranosyl-(12)--O-L-arabinopyranoside] 28-O-[-L-rhamnopyranosyl-(14)-O-(6-O-acetyl--D-glucopyranosyl)-(16)-O--D-glucopyranoside of echinocystic acid (glycoside L-G₀). The structures of the glycosides isolated have been established on the basis of chemical transformations and¹H and¹³C NMR spectroscopy.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 81–86, January–February, 1999.     

Some Pharmaceutical Properties of a New Branched Cyclodextrin, 6-O-α-(4-O- α-D-Glucuronyl)-D-glucosylβ-cyclodextrin

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.     

Auswertung der sterischen Hinderung von α,β-Diarylacrylnitrilen durch Korrelation polarographischer und HMO—LCAO-Angaben

Zusammenfassung Die Halbstufenpotentiale der polarographischen Reduktion einer Anzahl vontrans-,-Diarylacrylnitrilen [ArCH=C(Ar)CN (Ar=Phenyl-, 1- und 2-Naphthyl-; Ar=Phenyl-, 1- und 2-Naphthyl-, 4-Biphenylyl-, 9-Phenanthryl-, 9-Anthryl-, 1-Pyrenyl-)] inDMF wurden bestimmt. Die Abweichungen der experimentell ermittelten Halbstufenpotentiale von der Korrelation mit den Energien des ersten antibindenden Orbitals (HMO) für planare Systeme werden zur Bestimmung des Grades der sterischen Hinderung von 1-Naphthyl-, 9-Anthryl-, 1-Pyrenyl- und 9-Phenanthrylgruppen herangezogen. Die erhaltenen Werte für die Winkeldrehung dieser Reste stehen in Übereinstimmung mit den durch die Korrelation der IR-Frequenzen der CN-Gruppe mit der CN-Bindungsordnung ermittelten Drehwinkeln.

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Evaluation of steric hindrance in ,-diarylacrylonitriles by correlation of polarographic with HMO—LCAO data

The half-wave polarographic reduction potential of sometrans-,-diarylacrylonitrils Ar–CH=C(CN)Ar (Ar=phenyl-, 1- and 2-naphthyl-; Ar=phenyl-, 1- or 2-naphthyl-, 4-biphenylyl-, 9-phenanthryl-, 9-anthryl-, 1-pyrenyl-) have been measured in an aprotic medium (DMF). The deviations of the experimentally determined half-wave potentials from the correlation with the energies of the first antibonding orbital (HMO) for planar systems have been used for estimating the degree of nonplanarity in the conjugation of the 1-naphthyl, 9-anthryl, 1-pyrenyl and 9-phenanthryl groups. The so obtained rotation angle values agree well with the values calculated by means of the correlation of the CN stretching frequencies and the CN bond order.

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Mit 1 Abbildung     

Trans-cis Photoisomerization of 1-Methyl-4-(4′-hydroxystyryl)pyridinium in inclusion complexes ofβ-cyclodextrin and its derivatives

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.     

Phase diagram of the system dihexadecylphosphatidylcholine/dihexadecyl-phosphatidic acid/water/NaOH at pH=14

Differential-scanning-calorimetry, freeze-fracture electron microscopy, and³¹P-NMR spectroscopy were used to study the lyotropic and thermotropic properties of the system dihexadecylphosphatidylcholine/dihexadecylphosphatidic acid/water/ NaOH in dispersion with excess water at pH=14. The phase diagram showed that both phospholipids are demixed nearly completely in the gel phase. The coexistence of theP and theB -phase in the mixtures was pointed out in the freeze-fracture electron micrographs by the ripple structure (P -phase) and by the lamellar structure (B -phase).     

Synthesis of tetra- and pentacarbocyanine dyes with alkoxy groups in the β,β′ positions of the polymethine chain

Previously unknown symmetrical and unsymmetrical , '-dialkoxytetracarbocyanine and , '-dialkoxypentacarbocyanine dyes have been synthesized by the condensation of -alkoxy-substituted hexamethine and octamethine hemicyanines with quaternary salts of -alkoxypropenyl derivatives of heterocyclic bases. Tetracarbocyanines with a symmetrical structure have also been obtained by the direct interaction of quaternary salts of -alkoxypropenyl derivatives of heterocyclic bases with malonaldehyde dianil.     

Conformational studies of sequential polypeptides of L-Alanine and β-Alanine

Summary In order to investigate the effect of the -alanine residue on the conformational stability of -helical poly(L-alanine), studies have been made on the conformations of sequential copolypeptides having the following repeating sequences: (L-Ala--Ala) _n , (L-Ala-L-Ala--Ala) _n , (L-Ala--Ala-L-Ala-L-Ala) _n and (L-Ala-L-Ala-X) _n , where X is D,L--amino-isobutyric acid residue. Conformations of these polypeptides were measured both in the solution and solid states by means of optical rotatory dispersion, infrared and far-infrared spectroscopies and X-ray diffractions. All the copolypeptides studied here did not give the -helix. It may be, therefore, concluded that the -alanine residue is not incorporated in but impairs the -helix of poly(L-alanine), since the hydrogen bond periodicity in the -helical chain is disturbed by the introduction of such a -amino acid as -alanine.With 5 figures and 2 tables     

Application of the MIMS Technique to Study the Stability Constants of Small Organic Guest Molecules into Cyclodextrin Hosts in Aqueous Medium

In this work the potential of MIMS (Membrane Introduction Mass Spectrometry) for studying the inclusion of small organic guest molecules into cyclodextrin hosts in aqueous medium was investigated. MIMS profiles showed that the inclusion of benzene in cyclodextrins is favored in the following order: -CD HO-propyl--CD> -CD> -CD with equilibrium constants of K -CD = 404; K_HO-propyl-CD = 395, K _-CD = 335 and K _-CD = 210 M^-1 at 25 °C. Kinetic experiments suggested that under the conditions employed the inclusion process has a pseudo first-order dependence on the guest benzene concentration with the following order: -CD > -CD HO-propyl--CD> -CD. MIMS inclusion profiles of chlorobenzene and toluene showed that the presence of substituents in benzene makes the inclusion in -CD more difficult. Experiments with ferrocene--CD have also been carried out, showing that the complex rapidly dissociates in water and the resulting free -CD can complex with benzene present in the solution.     

Phase solubility analysis in studying the interaction of nifedipine with selected cyclodextrins in aqueous solution

The solubilizing potential and complexing tendencies of six cyclodextrins (CyD) with nifedipine in aqueous solution were evaluated using phase solubility methods. Solubility curves of nifedipine with -CyD, 2-hydroxypropyl--CyD (2HP--CyD) and 2-hydroxypropyl--cyclodextrin (2HP--CyD) were classified as type A_L, while for heptakis (2,6-dimethyl)--CyD (DIMEB), randomly methylated--CyD (RAMEB) and -CyD, A_p type phase behaviour was observed. Stability constants, calculated from phase solubility diagrams, decreased in the order: DIMEB > RAMEB > -CyD > 21HP--CyD > -CyD > 2HP--CyD.     

Isomerization of 3β-acetyl-α-3,4-epoxycarane

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.     

Binding of vitamin A byβ-cyclodextrin and heptakis(2,6-O-dimethyl)-β-cyclodextrin

Inclusion complexation of all-trans-retinol, retinal and retinoic acid with -cyclodextrin (-CD) and heptakis(2,6-O-dimethyl)--cyclodextrin (DM--CD) were investigated by means of UV-vis spectroscopy. The association constants (K _a) obtained for vitamin A with DM--CD is greater than with -CD. On the other hand, for the same host compoundK _a values of retinol, retinal and retinoic acid are very close to each other.     

Transformations of solasodine

Solasodine (I) has been subjected to a number of transformations. The following compounds have been obtained from it by described procedures: 3-acetoxypregna-5,16-dien-20-one (II), 3-acetoxypregn-5-en-20-ol (III), and 3-acetoxypregn-5-en-20-ol (IV). The oxidation of (III) and (IV), the formation of an oxime, and the reduction of the oxime with sodium in ethanol, followed by Hess methylation, has led to 20-dimethylaminopregn-5-en-3-ol (IX) and to 20-dimethylaminopregn-5-en-3-ol (X). From compounds (IX) and (X), by analogy with (III) and (IV) by their oxidation and the preparation of oximes, which were then reduced and methylated, the following were obtained: 3,20-bisdimethylaminopregnane (XVII) and 3,20-bisdimethylaminopregnane (XVIII), and also quaternary salts of the latter.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 370–374, May–June, 1980.     

Acylation of α, β- unsaturated ketones

,-Unsaturated ketones with a secondary -carbon atom (ethylideneacetone and n-butylidene-acetophenone) undergo acylation to give 2,6-di- and 2,5,6-trisubstituted pyrylium salts. A mechanism is proposed for the reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 735–737, June, 1973.     

A molecular mechanics study of the effect of substitution in position 1 on the conformational space of the oxytocin/vasopressin ring

Summary The effect of the substitution in position 1 on the low-energy conformations of the oxytocin/vasopressin 20-membered ring was investigated by means of molecular mechanics. Three representative substitutions were considered: -mercapto-,-dimethyl)propionic acid (Dmp), (-mercapto-,-cyclopentamethylene)propionic acid (Cpp), both forming strong antagonists, and (,-dimethyl--mercapto)propionic acid (-Dmp), forming analogs of strongly reduced biological activity, with the -mercaptopropionic (Mpa) residue taken as reference. Both ECEPP/2 (rigid valence geometry) and AMBER (flexible valence geometry) force fields were employed in the calculations. Three basic types of backbone conformations were taken into account which are distinguished by the type of -turn at residues 3 and 4: 1/III, II, and I/III, all types containing one or two intra-annular hydrogen bonds. The allowed (ring-closed) disulfide-bridge conformations were searched by an algorithm formulated in terms of scanning the disulfide-bridge torsional angle C-S-S-C. The ECEPP/2 and AMBER energies of the obtained conformations were found to be in reasonable agreement. Two of the low-energy conformers of the [Mpa¹]-compound agreed very well with the cyclic part of the two conformers found in the crystal structure of [Mpa¹]-oxytocin. An analysis of the effect of -substitution on relative energies showed that the conformations with the N-C-CH₂-CH₂ (₁) and C-CH₂-CH₂-S (₁) angles of the first residue around (–100°, 60°) and (100°, –60°) are not affected; this in most cases implies a left-handed disulfide bridge. In the case of -substitution the allowed values of ₁ are close to ± 60°. This requirement, being in contradiction to the one concerning -substitution, could explain the very low biological activity of the -substituted analogs. The conformational preferences of substituted compounds can largely be explained by the analysis of local interactions within the first residue. Based on the selection of the conformations which are low in energy for both the reference and -substituted compounds, two distinct types of possible binding conformations were proposed, the first one being similar to the crystal conformer with a left-handed disulfide bridge, the second one having a right-handed bridge, but a geometry different from that of the crystal conformer with the right-handed bridge. The first type of disulfide-bridge arrangement is equally favorable for both I/III and II types of backbone structure, while the second one is allowed only for the II type of backbone. No conformation of the I/III type has a low enough energy to be considered as a possible binding conformation for all of the active compounds studied in this work.     

Percolation Effects on the Surface of a Polyimide Film Modified with Aqueous Solutions of an Alkali and Acid

A cluster structure of the surface of a polypyromellitimide film was studied by the electron microscopy and ATR IR spectroscopy methods at different steps of consecutive treatment with aqueous solutions of an alkali and acid. The effective size and fractal dimension D of polyamidoacid clusters, as well as the degree _s of the filling of the surface with the latter were calculated from the data of the electron microscopy as a function of the degree of imide group conversion into amidoacid units on the film surface. The _s and D parameters were shown to increase with a rise in : _s = 0.1–0.3 and D = 1.3–1.4 at < _cr and _s 0.6 and D 1.7 at > _cr, where _cr is a critical degree of conversion, which corresponds to the formation of a continuous physical network of polyamidoacid macromolecules or a percolation cluster. In a region close to _cr (at < _cr), the correlation length land the concentration C of the clusters vary according to the laws of the percolation theory for two-dimensional lattices: l (_cr – )^– and C (_cr – ), where = 1.3 ± 0.1 and = 0.67 ± 0.05.     

Thebaine Cyclopropanation

[1+2]Cycloaddition to thebaine alcaloid under catalysis by copper triflate of carbene generated from CH₂N₂ occurred stereoselectively affording 6,7-methylene-6,7-dihydrothebaine. The simultaneously proceeding 8,14-cyclopropanation and nitrogen quaternization furnished N,N-dimethyl-N-nor-8,14-methylene-8,14-dihydrothebaine triflate whose structure was established by X-ray diffraction analysis. The possibility of preparation of 14-hydroxy-6,7-methylene-8-substituted dihydrocodeine derivatives was demonstrated.