Diisopropylethylamine → 3-{2-Ethyl-4-[5-(5-isobutyl-4-methyl-pyridin-2-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenyl}-propionic acid tert-butyl ester

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Reaction Steps

To a solution of 5-isobutyl-4-methyl-pyridine-2-carboxylic acid (246 mg, 1.07 mmol) and DIPEA (415 mg, 3.21 mmol) in DMF (4 mL), PyBOP (589 mg, 1.13 mmol) is added 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 (328 mg, 1.07 mmol) is added and stirring is continued for 1 h at 0° C. The reaction is quenched by adding water, the mixture is diluted with sat. aq. NaHCO3-solution and extracted twice with EA. The combined org. extracts are dried over MgSO4, filtered and concentrated to give the crude hydroxy-amidine ester intermediate; LC-MS: tR=1.10 min, [M+H]+=482.27. This material is dissolved in dioxane (10 mL) and the mixture is stirred at 80° C. for 15 h. The solvent is evaporated and the crude product is purified by CC on silica gel eluting with heptane:EA 7:3 to give 3-{2-ethyl-4-[5-(5-isobutyl-4-methyl-pyridin-2-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenyl}-propionic acid tert-butyl ester (420 mg) as a colourless oil; LC-MS: tR=1.26 min, [M+H]+=464.34.

Provenance & Evidence