Access to pyrrolo- and pyrido[1,2-a]indole derivatives by intramolecular nitrone cycloadditions. Effect of steric factors on the regioselective product formation.

On starting from N-allyl-substituted 2-indolecarbaldehydes and exploiting the intramolecular nitrone cycloaddition methodology, we synthesized a number of the title fused-ring indole derivatives in racemic as well as enantiopure form.