You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named (3S,4R)-4-phenyl-1-[(1S)-1-phenylethyl]-3-[(E)-prop-1-enyl]azetidin-2-one is given. What is its corresponding molecular formula?
user
C20H21NO
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