Aglycon moiety modifications

In all cases, 2,6-dideoxy sugars of the d- or L-series are common and important parts of these various molecules. In general, the specific therapeutic effect is thought to be caused by the aglycone, and the sugar residue to be responsible mainly for regulating the pharmacokinetics. Thus, parameters like bioavailability, resorption, distribution, or therapeutic width are influenced by the carbohydrate moieties. By modification of the carbohydrate moiety it is, e.g., possible to enhance the efficacy of unspecific aglycones like anthracyclines or aureolic acids, or also to reduce possible side effects. Such as approach is followed in the field of class-I and -II anthracyclines in order to decrease their considerable cardiotoxicity. 

Isolation and discovery of these biologically active compounds has encouraged researchers to carry out not only their total synthesis but also to accomphsh the synthesis of the aglycon [72-74] or modifications both in the cycHtol moiety and in the carbohydrate residue [75-82]. For instance, there are examples where the aminocyclopentitol motif has been replaced by either a six-membered polyhydroxylated carbocycle [83] or by a tetrahydropyrane moiety [84]. 

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