Carbohydrates dextrorotatory

In 1886, Brown11 discovered an organism which formed extremely tough membranes when cultivated m suitable nutrient solutions containing carbohydrates such as D-fructose, D-mannitol or D-glucose ethanol, sucrose or starch did not support membrane formation by this organism which Brown called Bacterium xylinum ) (Acetobacter xylinum). The membranes were readily soluble in cuprammonium hydroxide solution and yielded a dextrorotatory sugar upon acid hydrolysis. These properties and the results of combustion analysis led him to believe that the membrane was cellulose. 

A member of the vitamin-B complex it is a component of coenzyme A and may be considered a (3-alanine derivative with a peptide linkage. It is involved in the release of energy from carbohydrate utilization and is necessary for synthesis and degradation of fatty acids, sterols, and steroid hormones it also functions in the formation of porphyrins. It occurs in all living cells and tissues. The natural product is dextrorotatory [d(+)] and is the only form having vitamin activity. 

Raffinose, C18H32O16.5H2O, is the most important trisaccharide. It yields, as the name trisaccharide implies, three hexose molecules on hydrolysis. Raffinose occurs in the molasses obtained in the manufacture of sugar from beets, in cotton-seed, in barley, and in other grains. The hydrated crystals of raffinose lose their water at 100°. The anhydrous carbohydrate melts at 118°-119°, Raffinose is dextrorotatory for the hydrated form [a]i> = 104.5°. It does not reduce Fehling s solution. On hydrolysis of raffinose, levulose, dextrose, and galactose are formed. 

D-, L-, and DL- (roman small capital letters) must be reserved solely for compounds containing only one asymmetric carbon atom which can be unambiguously correlated with glyceraldehyde (this has known absolute configuration), and for proteins and carbohydrates (and closely related compounds) where D- and L- are used in speciahzed manners, covered by adequate reports 3. However, Fischer s use of d-and the carbohydrate chemists use of L- for dextrorotatory tartaric acid leads to repeated confusion it is thus preferable to use ( + )- and (- )- for the active 7 87... 

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