Linagliptin Impurity B Linagliptin iMpurity E 8-bromo-7-(but-2-ynyl)-3-methyl-1H-purine-2,6(3H,7H)-dione Linagliptin Impurity F Linagliptin Impurity 8 Linagliptin Impurity I Linagliptin Impurity M Linagliptin Impurity 23 Linagliptin Diene Impurity Linagliptin Impurity 7 Linagliptin Impurity 24 Linagliptin Impurity 29 Linagliptin Impurity 14 Linagliptin Impurity 4 Linagliptin Impurity 9 Linagliptin Impurity G Linagliptin Dimer Impurity 2 Linagliptin Impurity 5