4-[3-(3-Cyano-phenyl)-[1,2,4]oxadiazol-5-yl]-(S)-thiazolidine-3-carboxylic acid tert-butyl ester (212 mg, 20%, yellow oil) was prepared according to the procedure in Example 25 from Boc-L-thiazolidine-4-carboxylic acid (696 mg, 2.98 mmol) with isobutylchloroformate (0.43 ml, 3.28 mmol) and N-methylmorpholine (0.36 ml, 3.28 mmol) in THF (5 ml) at 40° C. for 2 h. Then 3-cyano-N-hydroxy-benzamidine (577 mg, 3.58 mmol) and additional N-methylmorpholine (0.39 ml, 3.58 mmol) and THF (4 ml) at room temperature overnight followed by extraction of the product and addition of DMF (2 ml) and the mixture was heated at 120° C. overnight. The crude residue was purified on silica gel using 20% ethyl acetate.
