Attempts to label cholesterol in ring B: seco-6-1-cholestan-7-one and seco-6-3(beta)-bromocholestan-7-one: ring A C14-labelled cholesterol.

Cholesterol is a waxy, crystalline substance of definite molecular weight, having the empirical formula C27H46O. Its melting point is 147.5 - 148.5°C. The established system of designating the rings by letter and the numbering of individual carbon atoms accompany the structure at this time. Hereafter, the location of various positions by number may be made by reference to this formula. The parent hydrocarbon, cholestane, may be derived by completely saturating cholesterol with hydrogen. This provides us with a basis of naming members of this series. Thus, cholesterol would be completely identified by Δ^5-cholesten-3 (β)-ol, where the Δ signifies a double bond and the superscript its position in the molecule. The symbols α and β refer to the orientation of substituents attached to the nucleus. Those bearing the symbol β are visualized as projecting above the plane of the paper and are shown by a solid line for the bond. α-oriented substituents are regarded as lying below the plane of the paper and are indicated by a dotted line for the bond. Cholesterol belongs to a class of organic compounds called sterols, which are crystalline alcohols(Gr. stereos, solid) and which are isolated from the unsaponifiable residues of lipids derived from animals and plants1. In recent years, this classification has been extended to include a great many other compounds, all having the same characteristic ring system, but differing in the side chain [...

Some recent developments in the synthesis of nucleosides

© 1970 Georg Thieme Verlag, Rudigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. The scope of this article includes recently developed, preparatively useful glycosylation methods involving the formation of a nucleoside bond. In addition, some innovations in the synthesis of the glycosyl halides used as starting materials in glycosylation procedures are briefly discussed