You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (4S)-4-[(3aR,7aR)-6-methyl-3-methylidene-2-oxo-3a,4,7,7a-tetrahydro-1-benzofuran-5-yl]pentanoic acid .
user
C15H20O4
assistant