Molecular characteristics of subfractions of laminarin

Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Russian Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 296–298, March–April, 1994.     

Avarol and isoavarol from a Pacific Ocean sponge Dysidea sp.

Two hydroquinone-group-containing terpenoids have been isolated from a Pacific Ocean spongeDysidia, sp. One of them has been identified by physicochemical methods as the previously known avarol. The second, isoavarol, obtained for the first time, differs from avarol by the 4(11)-position of the double bond.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, USSR Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 358–361, May–June, 1990.     

Nonanalytic features of the first order phase transition in the Ising model

The absence of the analytic continuation for the free energy near the point of the first order phase transition in thed-dimensional Ising model is proved. It is shown that thermodynamic functions in the metastable phase do not have certain values and can be derived only with an uncertainty. The asymptotic expansion near the point of the phase transition yields the values of thermodynamic functions with the same uncertainty.     

Structure of pseudostichoposide A — The main triterpene glycoside from the holothurian Pseudostichopus trachus

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 3β-{O-(3-O-methyl-β-D-quinovopyransoyl-(1 → 3)-O-β-D-xylopyranosyl-(1 → 4)-O-β-D-quinovopyranosyl-(1 → 2)-[4-O-(sodium sulfato)-β-D-xylopyranosyloxy]}-holost-7-en-22-one. Its native genin, which has been called urupogenin (3β-hydroxyholost-7-en-22-one) was obtained on partial hydrolysis in the form of an individual compound. It is a new holostane derivative.     

Reductive ethylation of homoallyl alcohols with a disubstituted double bond with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide

Homoallyl and bishomoallyl alcohols with a disubstituted double bond treated with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide are converted into the products of a reductive ethylation of the olefin fragment. Under similar conditions esters of β,γ-unsaturated carboxylic acids undergo a successive cyclopropanation of the ester group and reductive ethylation of the double carbon-carbon bond and yield 1-(3-ethylalkyl)cyclopropanols. The features of the observed reactions are explained in the framework of the carbometallation mechanism of the double carbon-carbon bond by the action of dialkoxytitanacyclopropane reagents.     

Triterpene glycosides of Pulsatilla dahurica structures of glycosides A,B, C,and D

The isolation of four triterpene glycosides from the roots of the dahurian anemonePulsatilla dahurica (Fisch. ex DC) Spreng, is described together with their identification, on the basis of chemical transformations, spectral characteristics, and literature analogies, as hederagenin 3-O--L-arabinoside, hederagenin 3-O-[O--D-glucopyranosyl-(12)--L-arabinopyranoside], hederagenin 3-O--L-arabinopyranoside 28-O-[O--L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranoside], and hederagenin 3-O-[O--D-glucopyranosyl-(14)--L-arabinopyranoside] 28-O-[O--L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranoside].Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 349–356, May–August, 1992.     

Untersuchungen an oxidischen Katalysatoren. XLII. Redoxverhalten des Nickels in NiNa?Y-Zeolithen 4. Einfluß der Zusammensetzung auf die Reduzierbarkeit von Nickel in NiNa?Y-Zeolithen

Studies on Oxide Catalysts. XLii. Redox Behaviour of Nickel in Zeolites NiNa? Y. 4. Influence of Composition on the Reducibility of Nickel in Zeolites NiNa? Y By chemical analysis (reaction with K₂Cr₂O₇) and ESCA investigations we determined the degree of reduction in reduced samples NiNa-Y as function of the mole ratio SiO₂/Al₂O₃ (module), of the Ni²⁺ degree of exchange and the kind of the second cations. (NH₄₊, Ca²+, Co²+, and Nd³+) in the temperature region of 620–770 K. The degree of nickel reduction increases with increasing module, decreasing degree of exchange and decreasing number of Brönsted acidic centres. This behaviour is caused by the influence of the interaction between cations Ni²⁺ and zeolite lattice on the reduction equilibrium.     

Beta Decay of the 134In Nucleus and Properties of N ≥ 81 Odd-Odd Neutron-Rich Indium Isotopes

Physics of Atomic Nuclei - The beta decay of the 134In nucleus, which is a neutron-rich odd-odd nucleus and which has an anomalously long lifetime, is studied in detail, and an attempt is made to...     

(Allylamino)silanes: Synthesis,Properties, and Prospects of Use in Producing New Materials

Russian Journal of General Chemistry - Methods for the synthesis and purification of dimethyldi(allylamino)silane, ethyldi(allylamino)silane, and methyltri(allylamino)silane were developed. The...