Alkylation of benzene by propane over zeolite-containing pentasil-alumina compositions and dealuminated pentasils

The alkylation of benzene by propane over pentasil-aluminum compositions (HTsVM--Al₂O₃) has been studied for a wide range of compositions and also over dealuminated and dehydroxylated samples. It has been established that Al₂O₃ plays little if any part in this reaction. As the proportion of HTsVM in the composition is increased the yield of alkyaromatic hydrocarbon increases, reaching a maximum (36%) for pure HTsVM. Dealumination and dehydroxylation of the HTsVM led to a significant reduction in the yield of alkylation products. It was concluded the Brønsted acid centers of the zeolite are responsible for bringing about the alkylation of benzene by the lower alkanes.DeceasedN. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2708–2712, December, 1992.     

Triterpene glycosides of Astragalus and their genins XXX. Cycloaraloside A from Astragalus amarus

In addition to -sitosterol, cyclosieversigenin, and -sitosterol -D-glucopyranoside, the roots of the plantAstragalus amarus Pall. (Leguminosae) have yielded a new triterpene glycoside of the cycloartane series — cycloaraloside A, which has the structure of 2OR,24S-epoxycycloartane-3,6,16,25-tetraol 3-O--D-glucopyranoside.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 806–809, November–December, 1989.     

Triterpene glycosides ofAstragalus and their genins. XLVIII. The structures of cycloalpigenin B and cycloalpioside B

The structures of the new cycloartane methylsteroid cycloalpigenin B and its glycoside cycloalpioside B, isolated fromAstragalus alopecurus Pall. (Leguminosae) have been determined on the basis of chemical transformations with the assistance of¹H and¹³C NMR spectroscopy and 2D NMR¹H-¹H and¹H-¹³C correlations of chemical signals and IR, CD, and electron-impact mass spectrometry. Cycloalpigenin B is 20R,24S-epoxycycloartane-3,12,16,25-tetraol. A transition from cycloalpigenin B to cycloalpigenin A has been achieved. Cycloalpioside B is 20R,24S-epoxycycloartane-3,12,16,25-tetraol 3-O--D-xylopyranoside.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, FAX (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 515–521, July–August, 1994.     

Triterpene Glycosides and Their Genins from Astragalus. LXIX. Orbigenin, the First Lanostanoid from Astragalus Plants

The new lanostane methylsteroid orbigenin, the structure of which is 23,24-lanost-9(11)-en-3,7,16,19,23,24,25-heptaol, was isolated from Astragalus orbiculatus Ledeb. (Leguminosae). The structure of the new triterpenoid, the first lanostanoid from plants of the Astragalus genus, was determined using electron-impact mass spectrometry and PMR and ¹³C NMR spectroscopies interpreted using J-modulation, DEPT, and the 2D NMR methods: ¹H-¹H COSY, HSQC, and HMBC.     

Effect of isomerization of amino acid residues on the structure of aquaporin

The effect of isomerization of amino acid residues on the structure and water permeability of aquaporin has been investigated. It was established that the equilibrium configuration of the model D isomer is energetically less favorable than that of its natural L isomer. It is shown that the model D isomer of aquaporin is waterproof.     

Triterpene glycosides and their genins fromThalictrum foetidum. II. The structure of cyclofoetigenin A

A glycoside isolated from the epigeal parts ofThalictrum foetidum (Ranunculaceae) has yielded a new genin — cyclofoetigenin A, the structure of which has been established on the basis of chemical transformations and spectral characteristics as 24S-cycloartane-3,16,25,25-tetraol.Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 370–375, May–June, 1985.     

Isoprenoids ofBryonia I. Pentacyclic triterpenes and sterol ofBryonia melanocarpa

The isoprenoid composition ofBryonia melanocarpa Nab. (Cucurbitaceae) has been studied. Eight components of the roots of this plant have been identified two pentacyclic triterpenoids: isomultiflorenol (1) and bryonolicacid (4); three phytosterols: (24R)-24-ethyl-5-cholest-7-en-3ß-ol (7), stigmasta-7E,24(28)-dien-3ß-ol (9), and 4cx-metlzylstigmasta-7E,24(28)-dien-3-ol(11); three sterol glycosides: (24R)-24-ethyl-5-cholest-7-en30-oi 3-O-ß-D-glucopyranoside (8), stigmasta-7E, 24(28)-dien-3ß-ol 3-O-ß-D-glucopyranoside (10), and 4-methylstigma-7E,24(28)-dien-3-ol 3-O-ß-D-glucopyranoside (12).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 402–409, May–June, 1995. Original article submitted October 9, 1994.     

Vinylnorbornene in the Ritter reaction

Reaction of vinylnorbornen with acetonitrile in the presence of H₂SO₄ at 20°C and 50°C was investigated.     

Kinetics of the crystallization of nanostructured disperse systems

The kinetics of the formation of crystalline colloidal structures upon the self-organization of ensembles of spherical nanoparticles in model metal lyosols is studied by the Brownian dynamics using realistic potentials of interparticle interaction. The effect of single factors (parameters of dispersed phase particles and characteristics of dispersion medium), as well as their set and arbitrary combinations on the rate of crystallization of sols and regularities of this process are analyzed.