You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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What is the molecular formula of the molecule tert-butyl 2-(9-chloro-6-oxo-4-oxabicyclo[5.3.1]undeca-1(11),7,9-trien-2-yl)piperidine-1-carboxylate ?
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C20H26ClNO4
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