The Isoquinoline Alkaloids

This chapter describes the alkaloids containing an isoquinoline or reduced isoquinoline ring-system. Structure determination and synthesis is discussed for the derivatives of isoquinoline and tetrahydroisoquinoline, which comprise of the simple tetrahydroisoquinolines, 1-Phenyltetrahydroisoquinolines, such as the cryptostylines, cherylline, and papaverin, one of the principal alkaloids of opium. Also synthetic methods including biosynthesis are shown for the cularines, the dibenzopyrrocoline alkaloids, pavinanes and isopavinanes, the bisbenzylisoquinolines, aporphinoids, the protoberberines, the protopine alkaloids, the phthalideisoquinoline alkaloids, the rhoeadines and papaverrubines, the benzo[c]phenanthridines, the spirobenzylisoquinolines, the Ipecacuanha alkaloids, colchicine, and 1-phenethylisoquinolines. It has become apparent, as the result of a large number of studies on the biosynthesis of the more highly condensed alkaloids of isoquinoline (protoberberins, protopines, aporphines, and so on) that norlaudanosoline may be regarded as the common precursor of all of them. The bisbenzylisoquinoline alkaloids, which are widely distributed in plants of the Menispermaceae family growing in South America and the Far East, and in Daphnandra, Berbis, Magnolia and Nectandra families, is one of the largest sub-groups of the isoquinoline alkaloids. The n.m.r, spectra of benzo[c]phenanthridines have attracted some attention, and are now of considerable importance in structural studies. The spectra of noravicine, nornitidine and norsanguinarine in trifluoracetic acid solution are highly characteristic.