To a solution of ethyl[(2-mercapto-4,5-dihydronaphtho[1,2-d]thiazol-6-yl)oxy]acetate (1.05 g, 3.27 mmol) in N,N-dimethylformamide (15 mL) were serially added 2,2-diphenylethyl iodide (1.11 g, 3.60 mmol) and potassium carbonate (500 mg, 3.60 mmol) and the mixture was stirred at 60° C. for 2 hours. This reaction mixture was diluted with water and extracted with ethyl acetate. The organic layer was washed with water and saturated aqueous sodium chloride solution, dried over MgSO4, filtered, and concentrated under reduced pressure to provide ethyl[[2-(2,2-diphenylethyl)thio-4,5-dihydronaphtho[1,2-d]thiazol-6-yl]oxy]acetate (1.11 g). To a solution of this compound (1.00 g, 1.99 mmol) in ethanol (45 mL)-water (5 mL) was added sodium periodate (0.51 g, 2.39 mmol) and the mixture was refluxed for 3 hours. To this reaction mixture were added-ethyl acetate and water, and the resulting two layers were separated. The aqueous layer was extracted with ethyl acetate and the pooled organic layer was washed with water, dried over MgSO4, filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane-ethyl acetate=1:8) and recrystallized from ethyl acetate to provide 0.64 g of the title compound. Yield 42%.
