Dielectric and13C NMR studies of sulfur dioxide-hydroquinone clathrates

Dielectric measurements of SO₂ quinol clathrates show that the reorientation of encaged SO₂ molecules is very rapid and depends greatly on the degree of cage occupancy. For a-quinol sample of cage occupancy = 0.57, the reorientation rate was 1 MHz at 6 K, with a reorientational activation energy of 673 J/mol. For a sample identified by¹³C NMR as-quinol, and for a-quinol sample with most cages filled with Xe, SO₂ reorientation rates are even greater, with activation energies of only some tens of J/mol. The low temperature dielectric studies show that some ethanol may be enclathrated in-quinol recrystallized from this solvent. The¹³C NMR spectra confirm the X-ray results that the lattice becomes distorted with increased SO₂ content.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

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     

Violurato complexes of nickel(II). Formation equilibria. Deprotonation equilibria of the coordinated ligands and related stereochemical changes

Summary The formation equilibria of nickel(II) violurato-complexes in water and dimethylsulphoxide-water (8020) as well as deprotonation of the coordinated ligands and related stereochemical changes are reported. The stability constants of the Ni²⁺-H₂V^– complexes log₁=5.06, Iog₂=9.38, log₃=12.98 as well as the acidity constants of the [Ni(H₂V)₃]^– complex, log_j1= 8.37, log_j2=15.76, log_j3=22.37 are determined at 25 °C and 0.1M NaClO₄. A new violurato-complex of Ni²⁺, Na₄[Ni(HV)₃]5H₂O, is isolated and characterized.     

Polarographische Bestimmung der Stabilitätskonstanten ammoniakalischer Magnesiumkomplexe

Zusammenfassung Die polarographische Methode des Indikatorions wurde zur Untersuchung der Komplexbildung des Mg²⁺-Ions mit Ammoniak verwendet. Es wurden die Stabilitätskonstanten ₁,₂,₃,₄ und ein annähernder Wert für ₅ bestimmt.

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Investigation of stability constants of magnesium ion-ammonia complexes

The polarographic method with indicator ion was used for investigation of magnesium ion complexation with ammonia. The numerical values of the stability constants ₁,₂,₃,₄ and the approximative value of ₅ were determined.

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Mit 2 Abbildungen     

Inclusion of Ring A of Cholesterol Inside the β-Cyclodextrin Cavity: Evidence from Oxidation Reactions and Structural Studies

The disposition of cholesterol inside the -cyclodextrin cavity(-CD) was deduced from oxidation of cholesterol secondary alcoholgroups by Ca(OCl)₂ and H₂O₂ in thepyridine–acetic acid system. The amount of cholest-4-ene-3-one formedwas found to be proportional to the concentration of -cyclodextrin,resulting in 56.1% of ketone. The oxidation rate was enhanced by-cyclodextrin and its methyl, polymer and 1 : 1copper(II)–-cyclodextrin derivatives. Detailed investigationsinvolving UV-visible, ¹³C- and ¹H-NMR(T₁, 1D NOE and ROESY) spectroscopic studies were carried out.A binding constant value of 15,385 ± 1500 M^-2 wasobtained for the 2 : 1heptakis-2,6-di-O-methyl--cyclodextrin(DM-CD) : cholesterolcomplex in chloroform from UV studies. Proton and solid state¹³C-CP MAS spectra of the -CD–cholesterol mixtureshowed large magnitude shifts for the protons from the wider end of the-CD cavity as well as those of ring A and ring B of cholesterol. Both1D NOE and ROESY measurements indicated the proximity between ring A andring B protons of cholesterol and the wider end protons of -CD andDM-CD. Besides, analysis of _c,_i and tau;_m from T₁measurements showed not only a lowering of rotational motions but a value of 0.016–0.048 for some of the cholesterol protons, typical of aweak complex. Based on these studies, a probable structure for the 2 : 1complex involving two molecules of -CD/DM-CD was proposed withportions of ring A and ring B being present inside the wider end of the-CD/DM-CD cavity and ring D and the side chain attached atposition 17, projecting into the wider end of the secondCD/DM-CD molecule.     

Structure of korseveridine

Summary The configuration 3, 15-dihydroxy-5, 9, 13, 12, 17, 22-⁸⁽¹⁴⁾-cevine has been proposed for korseveridine.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 2, pp. 101–106, 1968     

Comparison of the Complexation of Cosmetical and Pharmaceutical Compounds with γ-Cyclodextrin, 2-Hydroxypropyl-β-cyclodextrin and Water-Soluble β-Cyclodextrin-co-epichlorhydrin Polymers

The ability of different cyclodextrins (CDs): CD, 2-hydroxypropyl CD to complex drugs like 3--hydroxy-11-oxoolean- 12-en-30-oic acid, 2-ethylhexyl-3-(4-methoxyphenyl)-2-propanoate and menthol was compared to that of water-soluble polymers: CD-co-epichlorhydrin polymer (pCD/EP) and CD-co-epichlorhydrin polymer partially modified with trimethylammonium groups (pCD/EPN⁺). 3--Hydroxy-11-oxoolean-12-en-30-oic acid was poorly solubilized by CD compared with other CD derivatives, however the determination of the complexation constants was possible for pCD/EP, K₁₁ = 740, K₁₂ = 4, for pCD/EPN⁺, K₁₁ = 681, for CD, K₁₁ = 16 and for hydroxypropyl CD, K₁₁ = 114, K₁₂ = 3.4. A significant increase of the solubility was observed for 2-ethylhexyl-3-(4-methoxyphenyl)-2-propanoate with all host molecules, it was 916 times its solubility in pure water with pCD/EPN⁺, 1116 and 1300 times with 2-hydroxypropyl CD and pCD/EP respectively. The association constants are K₁₁ = 7970, K₁₁ = 4700, K₁₁ = 1470, K₁₁ = 230 and K₁₂ = 200 with pCD/EP, pCD/EPN⁺, CD, 2-hydroxypropyl CD respectively. An increase of the solubility of menthol was observed with all CD derivatives, up to 36–37 times, except for CD. The complexation constants are similar equal to about 200.     

Coordination compounds of hydrazine derivatives with transition metals. Part 24. Coordination chemistry of hydrazine-S-methyl carbodithioate schiff bases derived from β-dicarbonyl compounds

Summary The reactions of -diketones and -ketoaldehydes with hydrazine-S-methyl carbodithioate, hydth, have been studied in the absence and presence of metal(II) ions. A series of dimeric monoligand chelates [Ni(-dikhydth-2H)]₂ have been isolated. The reaction of these chelates with monodentate Lewis bases yields square planar [Ni(-dikhydth2H)B] chelates. Bisligand chelates of benzoylacetone monohydrazones [M(Bzachydth-H)₂] (M=Cu or Zn) have been also synthesized, as have a series of Ni^II and Zn^II chelates of -diketone bishydrazones of the type [M(-dik(hydth)₂-2H)].     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.     

The application of the pitzer equations to 1-1 electrolytes in mixed solvents

Pitzer's equation for the activity coefficient has been applied to LiCl, NaCl, KCl, RbCl, CsCl, and HCl in methanol-water mixtures at 25°C. The two parameters, _MX ⁽⁰⁾ and _MX ⁽¹⁾ , were obtained by the method of least squares. The same values of b and as for aqueous systems could be used for the methanol-water mixtures without greatly affecting the standard deviation of the fit. _MX ⁽⁰⁾ was found to decrease with methanol content for the alkali metal chlorides whereas _MX ⁽¹⁾ was found to increase. For HCl, however, a slight maximum and a minimum were found in the values of _MX ⁽⁰⁾ while a maximum was observed in the values of _MX ⁽¹⁾ .     

Measurement of concentration of calcium-45 in aqueous solutions with a silicon photodiode as a beta-ray detector

It was found that a commercial silicon photodiode modified only by removing its window can be used as a low-background detector of -rays from⁴⁵Ca solutions. We built a test system which could count -rays from 0.21% hot CaCl₂ solutions in the concentration range of 10^–5–10^–8M with linear sensitivity. Such a system using a small photodiode for real-time detection of -rays from small amounts of assay solutions could have many applications in the field of biophysics, biochemistry and physiology, e.g., in the study of Ca-binding proteins. This photodiode was also found to be suitable for measurement of low-energy -rays from¹⁴C.     

First Example of Construction of a Pyrrole Ring Bonded to a Steroid System by the Trofimov Reaction

The oxime of ⁵-pregnen-3-ol-20-one reacts with acetylene in the KOH-DMSO system to form a mixture of products containing 3-vinyloxy-17-(1-vinyl-2-pyrrolyl)-⁵-androstene as the major product (63% yield) and also the O-vinyloxime of 3-vinyloxy-⁵-pregnen-20-one (10%), 3-vinyloxy-17- and 3-vinyloxy-17-⁵-pregnen-20-one (25%, 1:4 ratio).     

Ultrasonic study of the molecular encapsulation and the micellization processes of dodecylethyldimethylammonium bromide-water solutions in the presence of β-cyclodextrin or 2,6-di-o-methyl-β-cyclodextrin

Aqueous solutions of -cyclodextrin (-CD) or 2,6-di-o-methyl--cyclodextrin (DM--CD) and dodecylethyldimethylammonium bromide (D₁₂EDMAB) have been studied from speed of sound (u) data at 298.15 K, using a pulse-echo-overlap technique. The molecular encapsulation process of the surfactant monomer into the cyclodextrin cavity and its effect in the micellization process of the surfactant have been analyzed from theu measurements: I) as a function of [D₁₂EDMAB] in the presence of several initial cyclodextrin concentrations (-CD or.DM--CD); II) as a function of [cyclodextrin] (-CD or DM--CD), for an initial micellar solution of D₁₂EDMAB and; III) as a function of the [cyclodextrin]/[surfactant] stoichiometric concentrations. Both inclusion complexes formed (-CDD₁₂EDMAB) and (DM--CDD₁₂EDMAB) have stoichiometries of 11, and their association constantK have been determined using a model proposed in this work, based on the additivity of the different contributions of the involved species to the speed of sound. The apparent critical micellar concentration, cmc^*, of D₁₂EDMAB is found to increase linearly upon the addition of cyclodextrin (-CD or DM--CD). The free surfactant concentration in the micellar region, [D₁₂EDMAB]_f, decreases in the presence of -CD and slightly increases in the presence of DM--CD. The influence of the parcial methylation of the -cyclodextrin (-CDDM--CD) and of the polar head of the surfactant (D₁₂TAB D₁₂EDMAB) on the complextion and micellar parameters are also discussed.Supplementary material available: Tables of speed of sound (14 pages) are available from the authors.     

Triterpene glycosides of Astragalus and their genins XLII. Cycloartanes of Astragalus tragacantha

Another six components ofAstragalus tragacantha Habl. have been identified on the basis of spectral characteristics and chemical transformations. We have previously described cyclocanthagenin and its 3-0--D-xylopyranoside — cyclocanthoside A — as products of the acid hydrolysis of cyclocanthoside D. Cyclocanthosides B, C, E, and G are here described for the first time and are (24S)-cycloartane-3,6,16,24,25-pentol 3-O-(4-O-acetyl--D-xylopyranoside) 6-O--D-glucopyranoside, (24S)-cycloartane-3,6,16,24,25-pentol 6-O-(6-O-acetyl--D-glucopyranoside) 3-O--D-xylopyranoside, (24S)-cycloartane-3,6, 16,24,25-pentol 6-O--D-glucopyranoside, and (24S)-cycloartane-3, 6, 16, 24, 25-pentol 6-O--D-glucopyranoside 3-O-[O--D-glucopyranosyl-(12)--D-xylopyranoside], respectively.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Institute of Ecological Genetics, Moldavian Academy of Sciences, Kishenev. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 360–367, May–August, 1992.     

Reaction of methylmagnesium iodide with steroid keto oxides

Summary The reaction of the 3-acetate of the 20-ketal of 16,17-oxido-⁵-pregnenol-3-one-20 with methylmagnesium iodide and subsequent hydrolysis of the reaction product yielded 16-methyl-⁵-pregnenediol-3 –17-one –20. 18-Nor-17-methyl-17-iso-^5.11-pregnadienediol-3,16-one-20 was formed as a by-product.     

Synthesis of 3-Cyano-4,6-bis(methylthio)pyrazolo[3,4-d]pyrimidine 1-riboside

3-Cyano-4,6-bis(methylthio)pyrazolo[3,4-d]pyrimidine was synthesized by cyclization of 3,4-dicyano-5-aminopyrazole with CS₂ in pyridine with subsequent Dimroth rearrangement and methylation of the resulting 3-cyano-4,6-dimercaptopyrazolo[3,4-d]-pyrimidine with methyl iodide. Glycosylation of the product by fusion with 1,2,3,5-tetra-O-acetyl--D-ribofuranose in the presence of iodine gave 1-(2,3,5-tri-O-acetyl--D-ribofuranosyl)-3-cyano-4,6-bis(methylthio)pyrazolo[3,4-d]pyrimidine, the deacetylation of which with a 1% solution of hydrogen chloride in methanol led to 3-cyano-4,6-bis(methylthio)pyrazolo[3,4-d]pyrimidine 1-fiboside. The structures of the compounds were established by IR, UV, circular dichroism, PMR, and ¹³NMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1687–1692, December, 1979.Original article submitted March 29, 1979.     

Preparation and Characterization of Branched β-Cyclodextrins Having Manno-Oligosaccharide Side Chains Derived from Yeast Mannan and Study of Their Functions

Branched -cyclodextrins (-CDs) having manno-oligosaccharide side chains were investigated. Three kinds of monobranched -CDs and five kinds of dibranched -CDs were chemically synthesized using the trichloroacetimidate method. Their structures were analyzed by HPLC, MS, and NMR spectroscopies. The specific interaction between those compounds and mannose-binding lectins (Concanavalin A and Pisum sativum agglutinin) was investigated by inhibition tests of hemagglutinating activity and by using an optical biosensor of the IAsys apparatus with a resonant mirror detector. The results showed that all branched -CDs interactedwith lectins. The binding affinity was 6¹,6⁴-(Man₃)₂- 6¹,6⁴-(Man₂)₂- > 6¹,6⁴-(Man₄)₂--CD when the derivatives were compared on the basis of side chain length and 6¹,6³- 6¹,6⁴- > 6¹,6²-(Man₂)₂--CD when compared on the basis of side chain position.     

Temperature-programmed desorption of hydrogen from Fe?Ni/Al2O3 catalysts

The aim of this paper is to investigate temperature activated hydrogen adsorption on Fe–Ni/Al₂O₃ catalyst and for the sake of comparison also on monometallic systems Fe/Al₂O₃ and Ni/Al₂O₃.

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- Fe–Ni/Al₂O₃ , , Fe/Al₂O₃ Ni/Al₂O₃.

     

Synthesis of chlorobis/β-diketonato/oxotechnetium/V/ and tris/β-diketonato/technetium/III/ complexes

Chlorobis/-diketonato/ oxotechnetium/V/ complexes [TcOCl/-dik/₂, -diketone=acetylacetone, benzoylacetone and dibenzoylmethane] were newly synthesized using macroamount of⁹⁹Tc. These complexes were further separated into geometrical isomers. Furthermore, an improvement of the yields for the syntheses of tris/-dike-tonato/technetium/III/ complexes [Tc/-dik/₃, -diketone=acetylacetone, benzoylacetone and 2-thenoyltrifluoroacetone] was examined using Tc/III/-thiourea complexes as a starting material.     

Effects of Modified β-Cyclodextrins on the Hydrolysis Reaction of p-Nitrophenyl α-Methoxyphenylacetate

Effects of -cyclodextrin (-CD) 1and its derivatives 2–7 on the deacylationreaction of p-nitrophenyl (R or S)--methoxyphenylacetatewere studied. The-CD derivatives used were6--D-glucosyl--CD 2, sulfated-CD (7–11 sulfate groups/CD ring) 3,dimethylated -CD 4, carboxymethylated-CD (3.5 carboxymethyl groups/CD ring) 5,2-tri(2-hydroxypropyl)--CD 6, and-CD appended on poly(allylamine) 7. Therate constant (k ^CD) of thesubstrate/-CD complexes and the formationconstants (K) of the complexes were determinedfrom the dependence of the pseudo-first order rateconstants of the deacylation reaction on theconcentration of -CDs. The order ofk ^CD for the R-enantiomer at pH8.0 is 45H₂O3 6 1 2 7, whilethat for the S-enantiomer is 4 5 6H₂O 1 2 3 7: H₂O denotes the rate in theabsence of -CDs. The order of K values is3 7 6 2 1 4 5. This work indicates that, though thesecondary hydroxyl groups of -CD play criticalroles in the deacylation reactions of the esterscomplexed with -CDs, the reactivity of theester/-CD complexes depends highly on thenature of the substituents at the secondary face of-CD. It also suggests that the substratesinserted from the secondary side as well as theprimary side of -CD of poly(allylamine)-bound-CD undergo the reaction by attack of aminogroups on the polymer chain.