Linagliptin Tartaric Acid Impurity 

Chemical Name: (2R,3R)-4-(((R)-1-(7-(but-2-yn-1-yl)-3-methyl-1-((4-methylquinazolin-2-yl)methyl)-2,6-dioxo-2,3,6,7-tetrahydro-1H-purin-8-yl)piperidin-3-yl)amino)-2,3-dihydroxy-4-oxobutanoic acid

Smile: O=C(N(C)C(N=C(N1CCC[C@@H](NC([C@H](O)[C@@H](O)C(O)=O)=O)C1)N2CC#CC)=C2C3=O)N3CC4=NC5=CC=CC=C5C(C)=N4