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 (4aS,7aR,12bS)-9-hydroxy-3-methyl-4a-prop-2-enoxy-2,4,5,6,7a,13-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7-one .
user
C20H23NO4
assistant