(2R,?3R)?-?2,?3-?Dihydroxy-?2-?methyl-butanedioic Acid 1,?4-?Diethyl Ester is an intermediate in synthesizing (2S,?3R)?-2-?Methyl-1,?2,?3,?4-?butanetetrol (M295075), a secondary organic aerosol formed through photooxidation of isoprene. It was identified as a glucide in methanol extracts of Carum ajowan fruit.