Highly diastereoselective synthesis of cis-β-lactams via [2+ 2] cycloaddition reactions of imines derived from a chiral bicyclic aldehyde and ketenes is described. The chiral bicyclic aldehyde as well as chiral acids were prepared from commercially available inexpensive isosorbide. The cycloaddition reaction was found to be highly diastereoselective; in some cases giving a single diastereomer of cis-azetidin-2-one in very good yields. A moderate ...