SYNTHESIS OF (+/-)-FERRUGININE AND (+/-)-ANHYDROECGONINE METHYL-ESTER BY A TANDEM CYCLOPROPANATION COPE REARRANGEMENT

Rhodium(II) acetate catalyzed decomposition of vinyldiazomethanes in the presence of N-(alkoxycarbonyl)pyrroles led to the synthesis of 8-azabicyclo[3.2.1]octa-2,6-dienes. The vinylcarbenoids generated from vinyldiazomethanes with a single electron-withdrawing group exhibited competing reactivity at the vinyl terminus in addition to the carbenoid site. Good regiocontrol was possible, however, by appropriate choice of catalyst and solvent. The practicality of this new approach to tropane alkaloids was demonstrated through short syntheses of (+/-)-ferruginine, (+/-)-anhydroecgonine methyl ester, and the lower homologue of (+/-)-anatoxin a.