Pyridocarbazole Alkaloids. Synthesis of Olivacine and Ellipticine Analogues

3,6-Dimethylellipticine and 1-demethyl-3,6-dimethylolivacine have been synthesized via the common intermediate 5-ethoxycarbonyl-3,5,6-tri- methyl-l1-oxo-5,11-dihydropyrido[4,3-blcarbazole.The reported antitumour activity of ellipticine and olivacine has generated a great deal of chemical interest in the synthesis of these pyridocarbazole alkaloids and their derivativesla'bRecently, we reported an approach to the construction of the pyridocarbazole skeleton2, which is capable of general application to a wide variety of analogues of the natural alkaloids.We now describe the convenient synthesis of two new compounds which represent per~pherally ring D modified 6-methylellipticine (1) -and 6-methylol~vacine (2).-The synthetic scheme employs, as starting material, the AB ring synthon 2, described by us pre-2 3 viously .