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 (3,9-dimethyl-2,7-dioxo-4-sulfooxy-3,3a,4,5,9a,9b-hexahydroazuleno[4,5-b]furan-6-yl)methyl 3-methylbutanoate .
user
C20H26O9S
assistant