158 



BIOCHEMICAL SYSTEMATICS 



H,CO 



H2CH2NH2 



mescaline 



ISOQUINOLINE ALKALOIDS 



This large group of alkaloids may be considered to be deriva- 

 tives of a parent substance, isoquinoline. Like the protoalkaloids they 

 may also be regarded as, potentially, derivatives of pathways con- 

 nected with aromatic amino acid synthesis. 



isoquinoline 



The isoquinoline alkaloids range from simple derivatives with 

 a reduced heterocyclic ring and minor substitutions of the benzene 

 ring to very complex alkaloids of the bis-benzylisoquinohne type. 

 The distribution of this more or less natural class of alkaloids is of con- 

 siderable interest and will be discussed in a following section. The 

 isoquinohne alkaloids are quite characteristic of the Papaveraceae 

 and certain other families. Representatives of the classes of iso- 

 quinoline derivatives are illustrated below: 



(a) Simple isoquinoline derivatives. 



NH 

 HO CH3 



anhalonidin 



(b) Benzylisoquinoline derivatives. 

 H3CO. 



CH2 



OCH, 



H3CO 



OCH3 



papoverin 



