CARBOHYDRATES 



37 



considerable importance in recent years because it is an intermediate 

 in the synthesis of vitamin C. It is produced on a commercial scale 

 by selective bacterial oxidation of D-sorbitol with Acetobacter suboxydans. 

 The necessary sorbitol is produced by the chemical reduction of D-glucose: 



The two amino sugars found in nature are related to common aldo- 

 hexoses and in each instance bear the amino group on carbon 2: 



CHO 



I 

 HC— NH2 



I 

 HOCH 



I 

 HCOH 



I 

 HCOH 



CHO 



I 

 HC— NH2 



I 

 HOCH 



I 

 HOCH 



I 

 HCOH 



CH2OH 

 D-Glucosamine 



CH2OH 

 D-Galactosamine 



D-Glucosamine (chitosamine) is the sole constituent sugar formed by 

 hydrolysis of chitin; it is also a component of mucin and several other 

 animal and bacterial polysaccharides. An unusual derivative, N-methyl- 

 L-glucosamine, is one of the components of streptomycin, an important 

 antibiotic. The chief natural occurrence of D-galactosamine (chondro- 

 samine) is as a component of chondroitin in cartilage (p. 67). 



Both sugars show the reactions of aldohexoses (reducing power, osa- 

 zone formation) and, in addition, have the basic properties of the amino 

 group. 



Desoxyhexoses 



These sugars, which are also known as methyl pentoses, lack, the 

 oxygen atom on carbon 6: 



