Glycosylation sugar carbonates

Glycosyl Sugar as a substituent bound at its anomeric carbon. 

Stabilities and colors of anthocyanins are dependent on the nature and number of sugars attached to the flavylium ion and the nature and number of acids linked to the glycosylic moiety. Tint and hue, however, are related to the numbers and positions of hydroxyl and methoxyl substituents in the flavylium ion. In addition, 3-deoxy-anthocyanins that are yellow due to dehydroxylation of the carbon at C-3 have higher stabilities than the corresponding 3-hydroxy anthocyanins that in turn are red but lose much of their stability. 

The anion of nitromethane adds easily to the carbonyl functions of sugars. This is a useful strategy for extension of the carbon chain.100 2-Acetamido-2-deoxy-P-D-glucose (A-acetyl-D-glucosamine) is the carbohydrate unit of glycoproteins that occurs most often. The nitromethy-lation method provides a straightforward route to a series of C-glycosyl compounds with the acetamido functionality (Eq. 3.62).101... 

The term glycal is used to define sugar derivatives having a double bond between C-1 and C-2. Accordingly, C-1 glycals are A1,2 unsaturated carbohydrate derivatives with a carbon substituent at the anomeric position. These compounds are versatile synthetic intermediates, owing to the variety of transformations associated with their enol ether functionality, and have found ample use in the preparation of C-glycosyl compounds,1 carbohydrate mimics,2 and natural products.3... 

Over thirty publications resulted from Tipson s work in Levene s laboratory. Along with the work on nucleic acid components, he also studied the structures of gum arabic and other plant gums, and conducted a range of synthetic investigations on sugars, with particular emphasis on uronic acids and 5-carbon ketoses. His 1939 observation that acetylated glycosyl halides... 

Scheme 15 General mechanism of glycosylation. The hydroxyl group of serine attacks the activated anomeric carbon of UDP-activated sugars.

---