decided that they could not know: for lactic acid or any other compound. Therefore Rosanoff proposed that one compound be chosen as a standard and a configuration be arbitrarily assigned to it. The compound chosen was glyceraldehyde because of its relationship to the sugars. The (þ) isomer was assigned the configuration shown in 39 and given the label D. The () isomer, designated to be 39, was given the label L.Once a standard was chosen, other compounds could then be related to it. For example, (þ)-glyceraldehyde, oxidized with mercuric oxide, gives ()-glyceric acid: