You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(3S,5R)-5-(2,3-dimethoxyphenyl)-7-ethyl-2-oxo-1,5-dihydro-4,1-benzoxazepin-3-yl] acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23NO6
assistant