You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1R)-1-[(3aR,4R,6aR)-4-(4-aminopyrrolo[2,3-d]pyrimidin-7-yl)-2,2-dimethyl-3a,4,6,6a-tetrahydrofuro[3,4-d][1,3]dioxol-6-yl]-6-chloro-1,4-dihydroisochromen-3-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H21ClN4O5
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