You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3,4,9-trihydroxy-6'-methoxy-1'-(3-methylbut-2-enyl)-6-(2-methylprop-1-enyl)spiro[1,7-diazatricyclo[7.3.0.03,7]dodecane-5,3'-indole]-2,2',8-trione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C27H33N3O7
assistant