ALKALOIDS 



159 



(c) Protoberberine derivatives. The basic berberine ring con- 

 figuration may be viewed as a benzylisoquinoline derivative in which 

 N-methylation is followed by condensation with the free phenyl 

 group. 



H.C 



OCH. 



OCH, 



bei'berine 



(d) Protopine derivatives. The protopine basic configuration 

 may be considered to arise by opening of the original heterocyclic 

 ring of isoquinoline in a protoberberine configuration. 



H2C 



protopine 



(e) Aporphine derivatives. These may also be regarded as 

 derivatives of the benzylisoquinoline type in which ring closure be- 

 tween the free-phenyl and the isoquinoline-phenyl ring occurs. 



NCH3 



H,CO 



(f) Phthalideisoquinoline derivatives. These constitute a 

 relatively small group which may be regarded as derivatives of 

 benzyhsoquinoline formed by a secondary ring closure to produce a 

 five-membered, oxygen-containing ring. This group of alkaloids is 

 found in the Papaveraceae, with the exception of hydrastine (below) 

 which is found only in Berberidaceae and Ranunculaceae. 



