anomereja

Anomereja, in English often referred to as anomers, are stereoisomers of cyclic carbohydrates that differ in configuration at the anomeric carbon. The anomeric carbon is the carbon that was the carbonyl carbon in the open-chain form and becomes a new stereocenter when the sugar cyclizes to form a hemiacetal or hemiketal. This unique center gives rise to two possible configurations, called alpha and beta.

In solution, monosaccharides can interconvert between these configurations through mutarotation. The process involves opening of the cyclic form to the linear form and re-closing in either orientation, allowing a dynamic equilibrium between the alpha and beta anomers. The relative amounts of each anomer depend on the sugar, solvent, and conditions such as pH.

A common way to designate anomeric configuration is in Haworth or Fischer projections. In many D-sugars, the alpha anomer has the anomeric hydroxyl group on the opposite side of the ring relative to the CH2OH group, while the beta anomer has it on the same side. For example, alpha- and beta-D-glucose are two anomers of glucose, existing in equilibrium in water.

Anomereja are especially important in glycosidic chemistry. When a sugar forms a glycosidic bond, the anomeric carbon may become involved in a covalent linkage, often locking the configuration and removing the free anomeric hydroxyl. The existence of alpha and beta forms can influence reactivity, recognition by enzymes and transport proteins, and the physical properties of carbohydrates.