Boc- (R) -3- amino -4- (2,4,5- three fluoro phenyl) butyric acid is an important intermediate for the preparation of cidartin. The first two peptide enzyme -IV (DPP-4) inhibitor approved by FDA in 2006 was used for the treatment of II type diabetes. Its use alone or combined with metformin and pioglitazone has obvious hypoglycemic effect, and is safe, well tolerated and less adverse reactions.