反应详情

To a solution of 2-(ethyl-methyl-amino)-6-methyl-isonicotinic acid (106 mg, 0.459 mmol) and DIPEA (178 mg, 1.38 mmol) in DMF (2 mL) is added PyBOP (253 mg, 0.486 mmol) at 0° C. The mixture is stirred for 15 min at 0° C. before 3-[2-ethyl-4-(N-hydroxycarbamimidoyl)-6-methyl-phenyl]-propionic acid tert-butyl ester (140 mg, 0.459 mmol) is added. Stirring is continued for 1 h at 0° C. The reaction mixture is diluted with water (2 mL) and sat. aq. NaHCO3-solution and extracted three times with diethyl ether. The combined org. extracts are dried over MgSO4, filtered and concentrated to give the crude hydroxyamidine ester intermediate; LC-MS: tR=0.92 min; [M+1]+=483.22. This material is dissolved in dioxane and then stirred at 80° C. for 15 h. The solvent is removed in vacuo to give crude 3-(2-ethyl-4-{5-[2-(ethyl-methyl-amino)-6-methyl-pyridin-4-yl]-[1,2,4]oxadiazol-3-yl}-6-methyl-phenyl)-propionic acid tert-butyl ester; LC-MS: tR=1.03 min; [M+1]+=463.31. The crude ester is dissolved in 6 N aq. HCl (10 mL) and stirred at 65° C. for 18 h. The mixture is concentrated and the crude product is purified by prep. TLC using DCM containing 11% of methanol as eluent to give 3-(2-ethyl-4-{5-[2-(ethyl-methyl-amino)-6-methyl-pyridin-4-yl]-[1,2,4]oxadiazol-3-yl}-6-methyl-phenyl)-propionic acid (5 mg) as a yellow resin; LC-MS: tR=0.89 min; [M+1]+=409.19.

1. additionis added
2. extractionextracted three times with diethyl ether
3. dry with materialextracts are dried over MgSO4
4. filtrationfiltered
5. concentrationconcentrated
6. customto give the crude hydroxyamidine ester intermediate
7. stirringstirred at 80° C. for 15 h
8. customThe solvent is removed in vacuo