Levorotatory tartaric acid having a dextro configuration. Although termed “unnatural,” its occurrence in nature has been demonstrated. Obtained in small amounts from racemic tartaric acid through biochemical cleavage using Penicillium notatum, Aspergillus griseus, A. niger or other microorganisms: Pasteur, Compt. Rend. 51, 298 (1860). Alternate route using salt formation with d-methylamphetamine: Walton, J. Soc. Chem. Ind. 64, 219 (1945). Monograph: K. Freudenberg, Stereochemie I, (1933), reprinted by J. W. Edwards (Ann Arbor, 1945). Crystallographic data: A. N. Winchell, The Optical Properties of Organic Compounds (Academic Press, New York, 2nd ed., 1954) p 47.