Difference between D L Sugars?
D and L are optical isomer of each other, or non superimposible
mirror images. The convention uses Glyceraldhyde as the reference.
In a fisher projection the OH of glyceraldehyde is on the right
side ( more improtantly in the R configuration)in the D isomer and
on the left side ( or the molecule is in the L configuration) in
the L isomer. So for all other sugars it looks at the last chiral
center for the molecule if the chiral center is R it is a D isomer
if the last chiral center is in the S configuration it is an L