You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Name the molecular formula for the molecule established as (3R,4S)-3-phenoxy-4-[(Z)-1-phenylprop-1-en-2-yl]-1-[(E)-prop-1-enyl]azetidin-2-one using the IUPAC nomenclature.
user
C21H21NO2
assistant