Regioselective synthesis of (Z)-5-methylene-containing morpholin-2-ones

An efficient, one-pot, protecting-group-free, and regioselective protocol to obtain enantiomerically pure (Z)-5-methylene-containing morpholin-2-ones, using α-amino acids and 5-bromo-4-methoxy enones as selective starting materials, is reported. The reaction was fully selective in providing the (Z)-regioisomer in all cases, regardless of the α-amino acid used; however, when a secondary amino group was used, only the (E)-isomer was observed. The synthesized compounds were obtained at yields of up to 92%, and their structure was unambiguously assigned by x-ray and 2D-NMR experiments.