Anhydrosugars

Anhydrosugars are carbohydrates that have undergone a dehydration reaction, meaning a molecule of water has been removed. This process typically occurs when two sugar molecules are linked together to form a disaccharide, or when a sugar molecule reacts with another molecule containing a hydroxyl group. In a more general sense, anhydrosugars can also refer to cyclic structures formed from a single monosaccharide molecule through an intramolecular dehydration.

The term "anhydro" signifies the absence of water. When a molecule of water is removed from a carbohydrate, a new chemical bond is formed. For example, the formation of sucrose, a disaccharide, from glucose and fructose involves the elimination of one molecule of water. Similarly, in the formation of polysaccharides like starch or cellulose, repeating units of monosaccharides are linked by glycosidic bonds, with the release of water in each linkage.

Intramolecular anhydrosugars are formed within a single sugar molecule. For instance, levoglucosan is an anhydrosugar derived from glucose. These compounds can be formed under specific chemical conditions, such as heating in the presence of an acid. Anhydrosugars play a role in various chemical processes and can be found as intermediates or products in carbohydrate metabolism and degradation. Their chemical properties differ from the parent sugar due to the altered structure and the presence of new functional groups or altered ring structures.