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system
Name the molecular formula for the molecule established as 3-[[(3S)-1-[(E)-4-aminobut-2-enoyl]pyrrolidin-3-yl]-ethylamino]-5-(2-methoxypyridin-4-yl)-1H-pyridin-2-one using the IUPAC nomenclature.
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C21H27N5O3
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