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.