|MadSci Network: Biochemistry|
All sugars of the same molecular weight are diastereomers (polystereomers) and/or constitutional isomers of one another. In addition, there are aldose/ketose isomers - sugar chemistry is one big puddle of isomeric compounds. Please consider 2-deoxy glucose versus 3-deoxy glucose -- these are positional isomers of one another.
The subject of isomerism in sugars occupies multiple volumes of relevant
research and nomenclature -- I suggest reading:
Try the links in the MadSci Library for more information on Biochemistry.