(+)-Diethyl L-tartrate is used as a chiral auxiliary in the Sharpless enantioselective epoxidation of allylic alcohols, for Sharpless-type enantioselective oxidation of sulfides to sulfoxides and as a chiral auxiliary in the enantioselective construction of cyclopropanes from allylic alcohols by an asymmetric Simmons-Smith reaction. It is also used as a chiral reagent in a host of chemical reactions, such as the synthesis of isoquinoline alkaloids and arundic acid, which has been used in acute ischemic stroke therapy.