Cardiac glycosides aglycones

The first examples of a consecutive radical 5 -exo-/dig-5-exo-dig cyclization of 1,5-diynes have been accomplished by the same researchers [43]. These authors were able to show that their cycloisomerization procedure provides access to strained semicyclic, conjugated dienes with a functionalized dioxatriquinane framework which occurs in the aglycones of steroidal cardiac glycosides, such as isogenine (3-96) [44] and C-norcardanolide (3-97) (Scheme 3.24) [45]. 

The carbohydrate part of various cardiac glycosides can be mono-, di-, tri-, and tetrasaccharide, and the aglycon (genin) is a steroid with certain unique structural characteristics. The main purpose of sugar residues is evidently to facilitate solubility of... 

The aglycone of this type of glycoside is biosynthetically derived from isoprene units. There are two major classes of isoprenoid glycosides saponins and cardiac glycosides. 

Scheme 5. Digitoxigenin and uzarigenin as aglycons of cardiac glycosides...

FIGURE 35.3 Structural formulas of the aglycones of the cardiac glycosides. 

Indications. Various colours are obtained with the cardiac glycosides, their aglycones, and certain oestrogens and corticosteroids. 

Cardiac glycosides consist of a five-ring cardenolide aglycon, called a genin, with a number of attached monosaccharides, which often include deoxysugars. These steroidal compounds are usually isolated from plant material (digitoxin, strophantidine), but they have been dis-... 

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