To a solution of 4-acetamidobenzenesulphonyl azide (140 mg) in acetonitrile (10 ml) was added, at room temperature, dimethyl 2-oxopropylphosphonate (97 mg). After stirring for 2 hours, 2-{3-[2-(1-{[3,5-bis(difluoromethyl)-1H-pyrazol-1-yl]acetyl}piperidin-4-yl)-1,3-thiazol-4-yl]-4,5-dihydro-1,2-oxazol-5-yl}benzaldehyde (267 mg) in methanol (2 ml) was added to the reaction mixture. After stirring for 8 hours, the reaction mixture was admixed with ethyl acetate and water and extracted with ethyl acetate. The organic extracts were dried over sodium sulphate and concentrated under reduced pressure. The residue was purified by chromatography. This gave tert-2-[3,5-bis(difluoromethyl)-1H-pyrazol-1-yl]-1-(4-{4-[5-(2-ethynylphenyl)-4,5-dihydro-1,2-oxazol-3-yl]-1,3-thiazol-2-yl}piperidin-1-yl)ethanone (50 mg).
