Arabinose-Derived Ketones as Catalysts for Asymmetric Epoxidation of Alkenes

Readily available arabinose-derived ketones, containing a tunable butane-2,3-diacetal as the steric
blocker, displayed increasing enantioselectivity (up to 90% ee) with the size of the acetal alkyl
group in catalytic asymmetric epoxidation of trans-disubstituted and trisubstituted alkenes. The
stereochemical communication between our ketone catalysts and the alkene substrates is mainly
due to steric effect, and electronic effect involving π−π interaction between phenyl groups of
substrate and of catalyst did not appear to be operative in our system.