Azirino(2',3':3,4)pyrrolo(1,2-a)indole-4,7-dione, 8-(((aminocarbonyl)oxy)methyl)-6-(((dimethylamino)methylene)amino)-1,1a,2,8,8a,8b-hexahydro-8a-methoxy-1,5-dimethyl-, (1aS-(1aalpha,8beta,8aalpha,8balpha))-