A mixture of 304 mg of (S)-2-tert-butoxycarbonylamino-3-(4-hydroxy-phenyl)-propionic acid methyl ester, 314 mg 2,3-dimethylpyridine-4-boronic acid, 374 mg cupric acetate, and 2 grams of powdered 4 Å molecular seives in 50 mL dry DCM and 0.75 mL TEA was stirred vigorously at rt under an O2 atmosphere for 40 h. The mixture was then poured into water-EtOAc. The organic layer was washed with water and saturated brine, dried over Na2SO4 and concentrated under reduced pressure. The residue was purified by column chromatography (DCM-EtOAc) to provide (S)-2-tert-Butoxycarbonylamino-3-[4-(2,3-dimethyl-pyridin-4-yloxy)-phenyl]-propionic acid methyl ester (18 mg). LCMS (m/z) 401.
