ANTITUMOR HETEROCYCLES .14. A NEW ROUTE TO PYRROLO[3,2-F]INDOLES AND THE NOVEL PYRROLO[3,2-F, 4,5-F']DIINDOLE SYSTEM

Vilsmeier formylation of the dipyrrolylmethane 14a gave the 8-formylpy rrolo[3,2-f]indole 15. Alternatively, condensation of the pyrrole 1a w ith a variety of 2,3-unsubstituted pyrroles 16a-e in the presence of M ontmorillonite K-10 clay gave, in general, the corresponding pyrrolo[3 ,2-f]indoles 19 and 21a-d. These pyrroloindoles were unambiguously str ucturally indentified by H-1 NMR spectra and NOE experiments, Amongst the by-products of the reaction were the corresponding pyrrolo [2,3-f] indoles, uncyclised 2-monosubstituted intermediate pyrroles and the 2, 3-disubstituted derivatives. Similar results were obtained by replacin g the ethyl ester la by the benzyl ester 1b. The pyrrole 1a, with K-10 clay and the tetrahydroindole 24 gave only a very low yield of the sp irocyclopentylpyrrolo [1,2-f]indole 25, but with the N-benzyl-4-oxotet rahydroindole 27b gave both the tetrahydropyrrolo[2,3-b]carbazole 28 a nd its [3,2-b] isomer 29 and other products. ]The pyrrole 1a condensed with N-methoxycarbonylpyrrole 32 to give the pyrrolo[3,2-f]indole 33, its isomer 34, the monosubstituted intermediate 35 and the two produc ts 36 and 37 resulting from disubstitution. Both of these (36 and 37) were cyclised with toluene-p-sulfonic acid to the novel pentacyclic py rrolo[3,2-f;4,5-f']diindole 38. Regiospecific hydrolysis and decarboxy lation of the N-methoxycarbonylpyrroloindole 33 gave the 2,3-unsubstit uted pyrrolo [3,2-f]indole 21k, which on Vilsmeier formylation gave th e 8-formyl derivative 39b.