sitagliptin [ 4-oxo-4-(3-(trifluoromethyl)-5,6-dihydro(1,2,4)triazolo(4,3-a)pyrazin-7(8H)-yl)-1-(2,4,5-trifluorophenyl)butan-2-amine,Januvia,MK 0431,MK-0431,MK0431,sitagliptin phosphate ] MK-0431 is the phosphate salt of the (2R)-isomer; inhibitor of DPP4 protein resulting in enhanced level of Glucagon-Like Peptide 1; structure in first source