ELECTROCYCLIZATION OF BETA-ARYLVINYL KETENIMINES - FORMAL SYNTHESES OF THE ALKALOID FROM MARINE ORIGIN, YDRO-7-METHOXY-1,6-DIMETHYLISOQUINOLINE-5,8-DIONE, AND 3-ETHOXYCARBONYLRENIEROL

A new six-step synthetic route for the preparation of the alkaloid fro m marine origin, 5,8-dihydro-7-methoxy-1,6-dimethylisoquino line-5,8-d ione is reported. The method is based on the electrocyclization of the appropriate beta-arylvinyl ketenimine, available by aza Wittig reacti on of the corresponding vinyl iminophosphorane with (trimethylsilyl)et henone followed by decarboxylation and further oxidative demethylation . Likewise, this method has successfully been applied to the preparati on of the 3-ethoxycarbonylrenierol.