Monosaccharides are the simplest form of carbohydrates. They may be classified based on the number of constituent carbon atoms. For instance, hexose is a monosaccharide with six carbon atoms. They may be further classified based on the functional group present. An aldose is a sugar with an aldehyde functional group whereas a ketose is a sugar with a ketone functional group. Altrose is one of the hexose monosaccharides and it belongs to the aldoses.
Altrose is a stereoisomer of glucose. It is also a C-3 epimer of mannose. Mannose is a hexose monosaccharide and also belongs to the aldoses. Altrose, glucose, and mannose have the same chemical formula, which is C6H12O6. Altrose, though, is a rare monosaccharide. Naturally-occurring form of altrose is the L-altrose (i.e. based on Fischer projection, can rotate the plane polarized light in counterclockwise direction). The D-altrose (i.e. can rotate the plane polarized light in clockwise direction) has not been found in nature. The L-altrose, in contrast, was isolated from the strains of the bacterium Butyrivibrio fibrisolvens.1
1 Altrose. (n.d.). Wikipedia.org. Retrieved from https://en.wikipedia.org/wiki/Altrose