An Oxazoline-Mediated Synthesis of the Pyrrolophenanthridine Alkaloids and Some Novel Derivatives.

An unsymmetrical biaryl coupling between the Grignard of N-benzyl-7-bromoindoline 25 and the appropriately substituted (o-methoxyaryl)oxazoline 15 leads to an intermediate biaryl which can be elaborated in one step to the 1H-pyrrolo[3,2,1-de]phenanthridine ring system. This simple two-step sequence provides general access to the pyrrolophenanthridine alkaloids 2−6.