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 (1S,9R)-3-(4-methoxyphenyl)-13-oxa-3-azatetracyclo[6.3.1.11,9.04,12]tridec-10-ene .
user
C18H21NO2
assistant