SYNTHESIS OF ISOQUINOLINE ALKALOIDS - TOTAL SYNTHESIS OF (+/-)-STYLOPINE

A total synthesis of (+/-)-stylopine [1], an alkaloid of the protoberberine type, was carried our: using a 3,4-dihydroisoquinoline [2]-boron tri fluoride complex and the propylenedithioacetal of methoxycarbonylpiperonal [3] as the main building blocks. The condensation product 4 was the key intermediate in the synthesis and was transformed either into stylopine [1] or 8-oxostylopine [5], as well as dihydrocoptisine [9].