Natural C-glycosides

AFP. See Antifreeze proteins (AFPs) Aglycones and aglycone reactions. See Natural C-glycosides Ramberg-Backlund reaction Reverse polarity (umpolung) approach to aryl C-glycoside synthesis Sialyl Lewis X (sLex)... 

C-Glycosidic linkages are present in various natural products and may inhibit glycosidases due to the structural analogy to their O-counterparts.42 Glycosyl phosphates 63 and 48 served successfully in the a-selective synthesis of aryl... 

C-Glycosides are typified by barbaloin, a component of the natural purgative drag cascara, but, as a group, the M-glycosides are perhaps the most important to biochemistry. Al-Glycosidic linkages are found in the nucleosides, components of DNA and RNA (see Section 14.1). In addition, nucleosides are essential parts of the structures of crucial biochemicals such as ATP, coenzyme A, NAD+, etc. The amine in these types of compound is part of a purine or pyrimidine base (see Section 14.1). 

While a full discussion of radical-mediated C-glycoside synthesis is beyond both the space available and the general remit of this chapter, illustrative examples of the nature of the transformations available will be described. Comprehensive reviews are, however, available [3,4] and should be consulted for more detailed accounts. 

The interest in C-glycosides increased greatly after 1970, when the pharmacological properties of some C-nucleosides (Fig. 2) of natural origin were observed [4]. 

Reviews (a) M. H. D. Poslema, Recent developments in the synthesis of C-glycosides, Tetrahedron 48 8545 (1992) (b) S. Hanessian and A. G. Pemet, Synthesis of naturally occurring C nucleosides, their analogs, and functionalized C-glycosyl precursors, Adv. Chem. Biochem. 33 111 (1976). 

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