Sugar Alcohols In the monosaccharide derivatives known as sugar alcohols, the carbonyl oxygen is reduced to a hydroxyl group. For example, D-glyceraldehyde can be reduced to glycerol. However, this sugar alcohol is no longer designated D or L. Why?

Because with reduction of the carbonyl oxygen to a hydroxyl group, the stereochemistry at C-1 and C-3 are the same; the glycerol molecule is not chiral.

Answer: This is due to total synthesis of the D or L derivatives

Explanation: In the case of D-glyceraldehyde, the D and L-glyceraldehyde derivatives are chirons that have been exploited extensively in the total synthesis of monosaccharides and analogs. The acetonide of d-glyceraldehyde ((R) - 37, (R) - 2,3-O-isopropylidene-d-glyceraldehyde) is most simply obtained from d-mannitol. d-Glyceraldehyde has been derived also from d-fructose, l-glyceraldehyde from l-sorbose.