A mixture of 50.3 mg of tert-butyl 4((6-chloropyridin-2-yl)methyl)-4-hydroxypiperidine-1-carboxylate, 19.3 mg of 2-aminothiazole, 9.0 mg of 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene, 4.8 mg of bis(dibenzylideneacetone)palladium(0), 25.2 mg of sodium carbonate and 0.77 ml of toluene was stirred at 100° C. overnight and 120° C. overnight. 156.6 mg of cesium carbonate, 94.4 mg of 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene and 47.1 mg of bis(dibenzylideneacetone)palladium(0) were added to the reaction mixture, followed by stirring the reaction mixture at 130° C. overnight. The reaction mixture was cooled to room temperature, and diluted with chloroform. An insoluble matter was filtered off using Celite, and the filtrate was concentrated in vacuo. The resulting residue was purified by a preparative thin-layer chromatography (Kieselgel™ 60F254, Art5744 (Merck), chloroform/methanol=10/1) to give the title compound as a brown oil.
