Ketotetroses

Ketotetroses are a class of monosaccharides, a type of carbohydrate, that contain four carbon atoms and a ketone functional group. The most common and simplest ketotetrose is erythrulose. The presence of a ketone group means that the carbonyl carbon is bonded to two other carbon atoms, and not to a hydrogen atom as in aldoses. In ketotetroses, this ketone group is located on the second carbon atom of the four-carbon chain. This structural feature distinguishes them from aldotetroses, which have an aldehyde group on the first carbon. The general chemical formula for ketotetroses is C4H8O4. Like other monosaccharides, ketotetroses can exist as open-chain forms or in cyclic hemiacetal or hemiketal forms. Due to the presence of chiral centers, ketotetroses can exist as stereoisomers. Erythrulose, for example, has two chiral centers, leading to D-erythrulose and L-erythrulose. These compounds are not as common as other carbohydrates in biological systems. Erythrulose is found naturally in some plants and is also used in sunless tanning products due to its ability to react with amino acids in the skin to produce melanoidins, which mimic a suntan.