Carba-Monosaccharides

5a-carba-a-D-galactopyranose FIGURE 8.3 The only natural carba-sugar. 

SCHEME 8.1 Carba-sugars as potential glycosidase inhibitors. 

This study was of course unrealizable with D-glucose itself because of mutarotation a carba-sugar, not affected by this drawback, is therefore a very useful chemical probe. 

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Similarly, anhydro derivatives of monosaccharides and disaccharides readily react with 359 to give the respective carba-di- and -tri-saccharide. 

Strictly speaking, the basic motif of a carbasugar possesses a carbohydrate counterpart, be it a real molecule or only hypothetically obtainable. To be precise, the carba counterpart of a monosaccharide arises from the replacement of the hemiacetal ring oxygen in carbohydrates by a carbon atom (usually a CH2), leaving the rest of the structure and chirality intact. In literature, however, this distinction does not appear to be so clear and often polyhydroxylated carbocyclic... 

Carba sugars are carbocyclic analogs of monosaccharides in which the ring-oxygen atom has been replaced by a methylene group. They were first synthesized by McCasland and coworkers,12 who called them pseudo-sugars, but they... 

The chemistry of carba sugars is quite similar to that of cyclitols both groups lack the latent carbonyl groups of their saccharide counterparts, and therefore fail to exhibit many of the characteristic properties of monosaccharides. Thus carba sugars and cyclitols do not form hydrazones or osazones, nor do they mutarotate, or reduce heavy-metal salts in base, in contrast to their oxidation products, the inososes. 

Data from "Si and C n.m.r. spectra of several 2-carba-3-oxa-homosllatranyl (20) and silatranyl (21) derivatives of monosaccharide and other alcohols have been reported. 

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