Aglycone, definition

Fig. 2. Definition of , h as H-l -C-l -X-C-Y, where X is the interglycosidic atom and Y is the attached carbon of the aglycone, and I h as C-l -X-C-Y-H-Y. The relationship with regard to heavy atoms is as follows For P-D-glycosyl compounds, < >o is 4>h — 120, whereas for a-D-glycosyl analogues, o is h + 120 and I c is 4>h + 120. (+) stands for +60 and

As seen from Table I, the 01 to C-l bonds, which join the glycosidic oxygen to the aglyconic carbon, have normal G-0 bond lengths for both the anomers. The similar bonds at the other end of the acetal grouping namely, the C-5 to 05 bonds appear somewhat shorter than normal. The 06 to C-l bonds are definitely shorter... 

DAG 652 and 178, but also their ribofuranosides were capable of inhibiting nucleic add synthesis. iV- -D-ribofuranosides and other glycosides of unsubstituted IbPs and IcPs, as well as their halo and nitro derivatives act similarly but less efficiently. For example, 3- -D-ribofuranosyl-IbP inhibits the reproduction of Ranikhet disease virus and shows to some extent an anticancer activity. However, the aglycone of IbP also shows definite activity towards E. coli phage. But 3- -D-ribofuranosyl-IcP does not possess any activity (63IJC30). 6-Bromo-IbP, its 2-methyl derivative, as well as... 

Hans Brockmann, a pioneer of research on antibiotics, pubhshed the isolation and structure elucidation of the first anthracyclines. According to his definition [1], anthracychnes are red to orange natural or synthetic dyes with a skeleton of 7,8,9,10-tetrahydro-tetracene-5,12-quinone and mono- to tetrasaccharide moieties attached, usually to ring D of the aglycone. In this review, the numbering system proposed by Brockmann (see structure 1) will be used. 

The exo-anomeric effect influences the rotations aroimdthe glycosidic C-1—O bond and is therefore important in determining the relative orientations of saccharide units in carbohydrate chains. The exo-anomeric effect is a balance between electronic and steric effects. The three staggered orientations for rotation about the glycosidic bond are not equivalent the exo-anomeric effect causes preference for the +synclinal orientation of the aglycone group in the a series and -synclinal for the series (see Fig. 18 for the definition of the torsion angle domains). 

The lack of a precise definition of a carbohydrate has led to somewhat arbitrary decisions as to whether border-line cases merit inclusion in our survey we have tried to assess likely interest to carbohydrate chemists, or whether significant carbohydrate chemistry is discussed in work focussed as much if not more on aglycone units. We apologize if our judgement does not always meet with your approval ... 

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