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 (1'S,9'R)-3',5',11',13'-tetrahydroxy-9'-(4-hydroxyphenyl)-6,8'-dioxospiro[cyclohexa-1,4-diene-3,16'-tetracyclo[7.6.1.02,7.010,15]hexadeca-2(7),3,5,10(15),11,13-hexaene]-1'-carboxylic acid .
user
C28H18O9
assistant