Triterpene glycosides ofAcanthophyllum gypsophiloides

Chemistry of Natural Compounds -     

On Direct and Inverse Problems of Logarithmic Potential With Finite Number of Parameters

We describe possibilities of realizing V. K. Ivanov’s method for solving inverse problems of logarithmic potential and that of A. V. Tsirul’skii’s method for solving direct problems of logarithmic potential. We solve two direct problems for logarithmic potential and for simple layer potential in the case of polygonal contour.     

Relativistic microwave devices with postacceleration of an electron beam in the interaction space

We analyzed the possibility of improving the efficiency of microwave devices operating with relativistic electron beams in systems with particle postacceleration in the interaction space. The fundamental feature of this approach is the formation of the accelerating-potential profile with the inherent electric field of a high-current electron beam. It is shown that the use of the space-variant beam-potential sag helps raise the estimated efficiencies of relativistic Cherenkov TWT and BWO up to values of about 50%.     

Triterpene glycosides ofAstragalus and their genins. XVII. Cycloasgenin B fromAstragalus tashkendicus

The roots ofAstragalus tashkendicus Bge. have yielded a new triterpenoid — cycloasgenin B – the structure of which has been established on the basis of chemical transformations and spectral characteristics as (24R)-6α,11α,16β,24,25-pentahydroxycycloartan-3-one.     

Phytoecdysteroids of plants of the genus Melandrium

The isolation and determination of the structure of the new phytoecdysteroid melandroside A are described; it is viticosterone E 22-O--D-galactopyranoside.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 517–520, July–August, 1991.     

Steroids of the spirostan and furostan series of plants of the Allium genus. XXIII. Structure of cepagenin and of alliospirosides C and D from Allium cepa

Two new steroid glycosides of the spirostan series have been isolated from the fruit ofAllium cepa L. (family Liliaceae): alliospirosides C and D. On the basis of chemical transformations and spectral characteristics it has been established that the aglycon of both glycosides is a new steroid sapogenin — cepagenin — having the structure of (24S,25R)-spirost-5-ene-1,3,24-triol. Alliospirosides C and D are cepagenin 1-O-[O--L-rhamnopyranosyl-(12)-L-arabinopyranoside] and 1-O-[O--L-rhamnopyranosyl-(12)-O--D-galactopyranoside], respectively.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 843–849, November–December, 1987.