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Name the molecular formula for the molecule established as 2-methylpropyl (6R)-6-(4-chlorophenyl)-8-methyl-4-oxo-3,6-dihydro-2H-pyrimido[2,1-b][1,3]thiazine-7-carboxylate using the IUPAC nomenclature.
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C19H21ClN2O3S
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