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 [(3aR,4S,6aR,8S,9S,9aS,9bR)-9-(chloromethyl)-8,9-dihydroxy-3,6-dimethylidene-2-oxo-3a,4,5,6a,7,8,9a,9b-octahydroazuleno[4,5-b]furan-4-yl] (2S)-2-methyloxirane-2-carboxylate .
user
C19H23ClO7
assistant