A New Approach to 5-Substituted Prolines and 2-Pyrrolecarboxylates

Abstract
Iodocyclisations of the allylic glycinates 7 lead either to the trans- or cis-2,5-disubstituted proline derivatives 8 or 9, depending on the reaction conditions; subsequent treatment of these with DBU in DMF gives the 2-pyrrolecarboxylates 10 and 13 in excellent yields by a double elimination of hydrogen iodide and toluenesulfinic acid.