You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance methyl (2R,5'aR,8'R,9'R,9'aS,10'aS)-8'-hydroxy-3-oxospiro[1H-indole-2,1'-3,5,5a,6,7,8,9,9a,10,10a-decahydro-2H-pyrrolo[1,2-b]isoquinoline]-9'-carboxylate .
user
C21H26N2O4
assistant