E. Reimann et H. Renz, PROTOBERBERINES FROM REISSERT COMPOUNDS .2. A NEW SYNTHESIS OF 8-METHYLDIBENZO[A,G]QUINOLIZIDINES, Archiv der pharmazie, 326(5), 1993, pp. 253-258
The Reissert compounds 16 are benzylated by 2-bromomethylacetophenone
dioxolane 14 to give the dihydroisoquinolines 5. Treatment of 5 with K
OH yields the 1-benzylisoquinolines 6 which spontaneously form the deo
xygenated coralynes 4 in acidic solution. 4a and 18 are reduced by NaB
H4 to give the 8-methyl-trans-dibenzoquinolizidines 19. The sequence 5
--> 6 --> 4 --> 19 is a new efficient access to coralyne analogues an
d 8-substituted tetrahydroprotoberberines.- Bromination of 2-methylace
tophenone does not lead to 2-bromomethylacetophenone but to the benzal
bromide 9 or to the phenacylbromide 11.