(5aS,5bS,8aS,9aR)-1-bromo-8a-hydroxy-8-methyl-5,5a,5b,6,8,8a,9,9a-octahydroimidazo[4',5':4,5]cyclopenta[1,2-e]pyrrolo[1,2-a]pyrazine-4,7-dione