 Another transformation of high synthetic utility is asymmetric epoxidation . A number of asymmetric <unk> exist : the Sharpless epoxidation , the Jacobsen @-@ <unk> epoxidation , and the Juliá @-@ Colonna <unk> . These methods require specific functionality in order to achieve selectivity . The Sharpless epoxidation is specific to <unk> alcohols , the Jacobsen epoxidation requires cis @-@ disubstituted aryl alkenes , and the Juliá epoxidation requires α @-@ β unsaturated ketones . Chiral <unk> act <unk> on many <unk> alkenes . It has even possible to effect <unk> epoxidation catalytically in the <unk> chiral unit . Further investigation into these reactions may be required before levels of <unk> excess become practical for large scale synthesis . <unk> et al. have investigated asymmetric epoxidation with a chiral <unk> salt using <unk> as the stoichiometric oxidant seen below . 
