Naturally Occurring 4-Oxy-l,2,3,4-tetrahydroisoquinolines

No simple 4-oxytetrahydroisoquinolines have been found thus far in nature. Structure 42 was originally proposed79 for the alkaloid gigan-tine. However, the structure was not confirmed by synthesis59 and a new structure (43) has been put forward.34 

Cohen and Collins69 have proposed that epinephrine (44) and similar compounds common in living tissue (i.e., the catecholamines) react with acetaldehyde formed in the body by oxidation of consumed ethanol to form 4-hydroxytetrahydroisoquinolines (45) [see Eq. (10)]. The latter compounds may play a role in alcohol toxicity. Given the presence of 

Two erythrine alkaloids, erythristemine (46)80 and erythrinine (47),81 contain 4-methoxy and 4-hydroxy groups, respectively, in a tetra-hydroisoquinoline ring, albeit highly substituted. 

---