Mitomycin B.

(1aS)-8α-[[(Aminocarbonyl)oxy]methyl]-1,1aα,2,8,8aα,8bα-hexahydro-1,5-dimethyl-8a-hydroxy-6-methoxyazirino[2',3':3,4]pyrrolo[1,2-a]indole-4,7-dione

[1aS-(1aalpha,8alpha,8aalpha,8balpha)]-8-[[(Aminocarbonyl)oxy]methyl]-1,1a,2,8,8a,8b-hexahydro-8a-hydroxy-6-methoxy-1,5-dimethyl-azirino[2',3':3,4]pyrrolo[1,2-a]indole-4,7-dione