NEW POTENTIAL DNA INTERCALATORS OF THE CARBAZOLE SERIES FROM INDOLE-2,3-QUINODIMETHANES - SYNTHESIS, CRYSTAL-STRUCTURE, AND MOLECULAR MODELING WITH A WATSON-CRICK MINI-HELIX

1-Alkylpyrano[3,4-b]indol-3-ones 3 react via a Diels-Alder step with an aryne or N-phenylmaleimide to furnish the new [b]annellated carbazoles 4-10 in a one-pot process. In an analogous procedure, the in situ generated N-benzoylindole-2,3-quinodimethane (13) reacted with quinones to furnish the dioxocarbazoles 14-16. Compounds 4 8 and 14-16 with a coplanar skeleton are members of a class of potential DNA intercalators, as has been shown for 5 and 8 by X-ray structural analysis. On the basis of the geometries determined by X-ray crystallography, the intercalative binding of these molecules with a Watson-Crick mini-helix was predicted by molecular modeling methods,