Regio- and enantioselective catalytic cyclization of pyrroles onto N-acyliminium ions

The regio- and enantioselective cyclization of pyrroles onto N-acyliminium ions generated in situ from hydroxylactams is reported. Modest to excellent ee's and yields are obtained in these novel Pictet-Spengler-type reactions with a chiral thiourea-pyrrole catalyst. Useful synthetic transformations of the versatile pyrroloindolizidinone and pyrroloquinolizidinone products are presented.