IMPROVED SYNTHESES OF (-LENTIGINOSINE AND (1S,2S,7R,8AS)-TRIHYDROXYOCTAHYDROINDOLIZINE BY BUTENOL CYCLOADDITION TO ENANTIOPURE PROTECTED DIHYDROXY PYRROLINE N-OXIDES())

The amyloglucosidases inhibitors (+)-lentiginosine (1) and (1S,2S,7R,8 aS)-1,2,7-trihydroxyoctahydroindolizine (2) have been synthesized in h igh overall yield via nitrone cycloaddition to butenol employing an en antiomerically pure L-tartaric acid derived nitrone 5a. These synthese s profit of a highly regio- and stereoselective cycloaddition and prov ide the target compounds with yields increased of an order of magnitud e with respect to previous reports.