Tembetarine chloride

Since it is known that quaternary salts give better yields of phenolic oxidative coupling products than do tertiary bases, when oxidised with one-electron transfer agents in the laboratory, the possible role of reticuline methochloride (tembetarine chloride) in the biogenesis of more complex alkaloids has been examined. The labelled salt has been found to be very poorly incorporated into morphine, sinomenine, and protopine. 

R )-(—)-Armepavine (7b) was isolated from Rhamnus frangula (Rhamnaceae) (335). The tembetarine chloride [methochloride of reticuline (7f)] was isolated from Fagara naranjillo (Griseb.) (336). 

Although in P. somniferum and Sinomenium acutum the biosynthesis of the morphinane bases can be carried out with (+)-reticuline as starting material, these bases and also protopine (101a) cannot be obtained biosyn-thetically in satisfactory yield from (+)-tembetarine chloride (reticuline methochloride). Similar results were obtained with D. spectabilis (683). Important intermediates of the biosynthesis between tetrahydroprotober-berine and protopine alkaloids are the compounds of the dihydroprotopine type (102), which were prepared in high yield by partial synthesis with cyanogen bromide (von Braun method) (684). The biosynthesis of pro topine alkaloids is also discussed in Section III,N. 

Tembetarine (LXI) on oxidation with ferric chloride at room temperature afforded the quaternary aporphine alkaloid (+ )-laurifoline (LXVIII) 120). 

---