Question

Trehalose is a nonreducing disaccharide (C₁₂H₂₂O₁₁) isolated from the poisonous mushroom Amanita muscaria. Treatment with an α -glucosidase converts trehalose to two molecules of glucose, but no reaction occurs when trehalose is treated with a β -glucosidase. When trehalose is methylated by dimethyl sulfate in mild base and then hydrolyzed, the only product is 2,3,4,6-tetra-O-methylglucose. Propose a complete structure and systematic name for trehalose.

Short answer

Trehalose:

α -D-glucopyranosyl-α -D-glucopyranoside:

Step-by-step solution

Structure elucidation of trehalose:

Trehalose is a disaccharide which is non-reducing in nature and is found in bacteria, yeast etc. Treatment of trehalose with α -glucosidase gives two molecules of glucose which indicates that it consists of two molecules of glucose which must be linked by α -linkage at anomeric carbons which are depicted by wedge-dash bonds in the structure of trehalose.

When trehalose is methylated by dimethyl sulfate in mild base followed by hydrolysis, the product obtained is 2,3,4,6-tetra-O-methylglucose which indicates that glucose molecule must be in the structure of trehalose as that’s why product is tetra-O-methylated.

Two molecules of glucose-product obtained when trehalose is treated with α -glucosidase.

2,3,4,6-tetra-O-methylglucose-Product obtained after hydrolysis of trehalose.

Systematic name of trehalose:

The glycosidic linkage is named in prefix before naming the glycosyl and glycoside sugars which are written afterwards respectively. O-locants if present are written in the prefix before glycosidic linkage name. In trehalose, both sugars present are glucose, thus, the systematic name of disaccharide trehalose will be α -D-glucopyranosyl-α -D-glucopyranoside.

α -D-glucopyranosyl-α -D-glucopyranoside