(2R,3R)-2-Methyl-1,4-dioxaspiro[4.4]nonane-2,3-dicarboxylic Acid 2,3-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.