Brivaracetam Impurity 13 Catalogue B332543 CAS 2432911-32-3 M.W 297.40 M.F C15H27N3O3 Specifications FAQs (S)-N-((S)-1-amino-1-oxobutan-2-yl)-2-((R)-2-oxo-4-propylpyrrolidin-1-yl)butanamide