You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3S,3'aR,8'aR,8'bS)-6,7-dimethyl-2'-(2-methyl-3-nitrophenyl)spiro[1H-indole-3,4'-3a,6,7,8,8a,8b-hexahydropyrrolo[3,4-a]pyrrolizine]-1',2,3'-trione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C25H24N4O5
assistant