Examples involving complex substrates and 'exotic' ylides have been reported, as shown below. The reaction has been used in a number of notable total syntheses including the Danishefsky Taxol total synthesis, which produces the chemotherapeutic drug taxol, and the Kuehne Strychnine total synthesis which produces the pesticide strychnine. The synthesis of aziridines from imines is another important application of the Johnson–Corey–Chaykovsky reaction and provides an alternative to amine transfer from oxaziridines. Though less widely applied, the reaction has a similar substrate scope and functional group tolerance to the carbonyl equivalent. The examples shown below are representative; in the latter, an aziridine forms "in situ" and is opened via nucleophilic attack to form the corresponding amine. For addition of sulfur ylides to enones, higher 1,4-selectivity is typically obtained with sulfoxonium reagents than with sulfonium reagents. Many electron-withdrawing groups have been shown compatible with the reaction including ketones, esters, and amides (the example below involves a Weinreb amide). With further conjugated systems 1,6-addition tends to predominate over 1,4-addition. In addition to the reactions originally reported by Johnson, Corey, and Chaykovsky, sulfur ylides have been used for a number of related homologation reactions that tend to be grouped under the same name. The development of an enantioselective (i.e. yielding an enantiomeric excess, which is labelled as "ee") variant of the Johnson–Corey–Chaykovsky reaction remains an active area of academic research. The use of chiral sulfides in a stoichiometric fashion has proved more successful than the corresponding catalytic variants, but the substrate scope is still limited in all cases. The catalytic variants have been developed almost exclusively for enantioselective purposes; typical organosulfide reagents are not prohibitively expensive and the racemic reactions can be carried out with equimolar amounts of ylide without raising costs significantly. Chiral sulfides, on the other hand, are more costly to prepare, spurring the advancement of catalytic enantioselective methods. The most successful reagents employed in a stoichiometric fashion are shown below. The first is a bicyclic oxathiane that has been employed in the synthesis of the β-adrenergic compound "dichloroisoproterenol" (DCI) but is limited by the availability of only one enantiomer of the reagent.