 The Fischer diagrams of the eight -aldohexoses are the mirror images of the corresponding -isomers; with all hydoxyls reversed, including the one on carbon 5.A ketohexose is a ketone-containing hexose Biologically, the most important example is fructose.In the linear form, the 2-ketohexoses have three chiral centers and therefore eight possible stereoisomers (23), comprising four pairs of enantiomers.