Synthesis of the mitomycin and FR900482 ring systems via dimethyldioxirane oxidation.

[reaction: see text] Dimethyldioxirane oxidizes a 2,3-dihydo-1H-pyrrolo[1,2-a]indole unsubstituted at the C-9 position stereoselectively to form a hydroxy ketone with all the basic elements of the mitomycin ring system. On the other hand, a 2,3-dihydo-1H-pyrrolo[1,2-a]indole derivative substituted with an alkyl group at C-9 undergoes an oxidative ring expansion in the presence of dimethyldioxirane to give an FR900482 analogue.