The present invention discloses a process for preparing (R)-2-[[6-(3-Aminopiperidin-1-yl)-3-methyl-2, 4-dioxo-3, 4-dihydropyrimidin-1(2H)-yl] methyl]-4-fluorobenzonitrile succinate known as Trelagliptin succinate of formula-II.La présente invention concerne un procédé de préparation de (R)-2- [[6- (3-aminopipéridin-1-yle)-3-méthyl-2, 4-dioxo-3, 4-dihydropyrimidin-1 (2H)-yle] méthyl]-4-fluorobenzonitrile succinate connu sous lappellation de succinate de trélagliptine de formule-II.