An enantioselective route to pyrrolidines: removal of the chiral template from homochiral pyrroloimidazoles

Two-step reductive removal of the chiral template from optically active pyrroloimidazoles, available from 1,3-dipolar cycloaddition of homochiral 4,5-dihydroimidazolium ylides, gives optically active substituted pyrrolidines. Selective manipulation of the substituents affords, e.g., naturally occurring and other optically active proline derivatives, and optically active pyrrolizidines and indolizidines.