Chemical Transformation of Protoberberines. VIII. A Novel Synthesis of (+/-)-Fumaricine and a Formal Synthesis of (+/-)-Alpinigenine
Berberine (1) was transformed stereoselectively into either the trans- or cis-hydroxyspirobenzylisoquinoline (9 or 10) via the 8,14-cycloberbine (3).This method was applied to a first transformation of the protoberberine (22) into a spirobenzylisoquinolin