Below is the open-chain structure of the monosaccharide D-tagatose, which is a ketohexose. Like most monosaccharides, it has more than one chiral carbon. Select all of the chiral carbon atoms.
Identify the chiral atoms by selecting each atom and assigning it a map number of 1 until all atoms are mapped. To
do this, right-click on an atom and choose Atom Properties. (Mac users: Use an equivalent for right-clicking.)
Then, clear the check mark to enable the Map field before entering a value.