Enantioselective Chemoenzymatic Synthesis of trans-Aziridines

A straightforward, five-step procedure for the synthesis of enantiomerically pure 2,3-disubstituted trans-aziridines has been developed starting from commercially available aldehydes. Hydroxynitrile lyase-mediated cyanohydrin formation provided cyanohydrins in excellent enantioselectivities and good yields. Subsequent formation of diastereomerically pure anti-amino alcohols via a one-pot Grignard addition-reduction sequence, Cu-II-catalyzed diazotransfer, and triphenylphosphine-mediated reductive cyclization provided the corresponding trans-aziridines in good yields and excellent diastereoselectivities.