Reducing disaccharides, structure

In 1935, Zemplen applied the Wohl reaction to octa-O-acetylcello-biononitrile,40 and obtained amorphous, nitrogenated substances that he supposed to be acetamido derivatives. His aim being the demonstration of the structure of the reducing disaccharides through successive degradation of their acylated nitriles to the lower aldo-biose, he discontinued these studies. 

The structure of planteose (2) was deduced by French and coworkers80,80 by use of chemical and enzymic methods. Partial hydrolysis of planteose with acid yields D-glucose and a reducing disaccharide, namely, planteobiose (see Section II,5,a). 

An unknown reducing disaccharide is found to be unaffected by invertase enzymes. Treatment with an a-galactosidase cleaves the disaccharide to give one molecule of D-fructose and one molecule of D-galactose. When the disaccharide is treated with excess iodomethane and silver oxide and then hydrolyzed in dilute acid, the products are 2,3,4,6-tetra-(9-methyl-galactose and 1,3,4-tri-O-methylfructose. Propose a structure for this disaccharide, and give its complete systematic name. 

The nature of the sugars in a nonenzymic browning reaction determines their reactivity. Reactivity is related to their conformational stability or to the amount of open-chain structure present in solution. Pentoses are more reactive than hexoses, and hexoses more than reducing disaccharides. Nonreducing disaccharides only react after hydrolysis has taken place. The order of reactivity of some of the aldohexoses is mannose is more reactive than galactose, which is more reactive than glucose. 

In common with other reducing disaccharides, lactose undergoes the usual reactions of aldoses, although precautions must be taken to prevent hydrolysis of the glycosidic bond. Furanoid structures cannot be formed, however, because of the presence of the (1 —> 4)-linkage. 

Thus it is clearly visible that they are about 40-50 K higher than the value of Tg evaluated on the basis of dielectric measurements for acetyl derivative of lactose. It is surely related to the fact that molecules of the reduced disaccharide form strong hydrogen bonds and mainly these interactions are responsible for so significant difference in the glass transition temperatures of the both investigated herein carbohydrates. Influence of hydrogen bonds on structural... 

A. S. Perlin, Structure of reducing disaccharides by lead tetraacetate oxidation, Anal. Chem., 27 (1955) 396-399. 

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