Structure of xanthalin

Chemistry of Natural Compounds - 1. Xanthalin has been shown to have the structure of 2′, 2′-dimethyl-3′, 4′,-diangeloyloxy-3′, 4′-dihydropyrano-5′,...     

The structure of arnifolin

Summary Structure (I) is proposed for arnifolin — a sesquiterpene lactone fromArnica foliosa Nutt. andArnica montana L.All-Union Scientific-Research Institute for Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 270–272, May–June, 1971.     

膜荚黄芪苷的结构

前文报道从中药膜荚黄芪(Astragalus membranaceus Bunge)根部分离得到三个皂苷ASI、AS Ⅱ和 AS Ⅲ.AS Ⅰ和 AS Ⅱ分别称为膜荚黄芪苷(astramembrannin)Ⅰ(1)和Ⅱ(2),AS Ⅲ经鉴定为胡罗卜苷(dancosterin)(3).本文报道1和2的结构测定.1为主要成份,具有降压、抗炎、镇静、镇痛和调节代谢的作用.1和2经 Smith 降解均得苷元4~(**),用酸水解经鉴定1含有木糖和葡萄糖,2仅含木糖.     

The structure of phosphacymantrene

Proton NMR spectra of phosphacymantrene (π-phospholyl manganese tricarbonyl) orientated in the nematic phases of liquid crystals have been investigated. The derived H-H and H-P direct dipolar coupling constants have been used to determine the relative proton-proton and proton-phosphorus distances. A comparison of the geometrical data of various 5-membered aromatic heterocycles shows that the relative distances between the protons closest to the heteroatom increase with the van der Waals radius of the heteroatom. The results suggest that NMR spectroscopy of orientated molecules can be used to determine van der Waals radii.     

The structure of nitrarine

Summary Dehydrogenation of the alkaloid nitrarine with selenium has given 3-(quinolin-8-yl)--carboline (II) and 3-(5, 6, 7, 8-tetrahydroquinolin-8-yl)--carboline (III).On the basis of the results of a study of the chemical and physical properties of nitrarine, and also from the results of x-ray structural analysis, structure (I) has been established for it.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow, Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–345, May–June, 1976.     

The structure of luteicine

An investigation of the UV, IR, PMR, and mass spectra and chemical transformations of luteicine have established for it the structure of 11-hydroxy-2,13-dimethoxyhexahydro-1,13-epoxyhomoproaporphine. The structure of the base was confirmed by its partial synthesis from luteidine.     

The structure of silylcycloheptatrienes

Calculations have been made, using the MNDO method, of the structures and energies of four isomeric forms of η⁷-SiH₃C₇H₇ and of η₇-SiH₃C₇H₇. The transition state has been identified for the [1,5] shift of the SiH₃ group in η¹-SiH₃C₇H₇, but no transition state could be located for any other SiH₃ migration pathway: this is consistent with orbital-symmetry control of the rearrangement. Conformational preferences in 7-substituted cycloheptatrienes and 1-substituted cyclohexanes are briefly compared.