A solution of 2-difluoromethoxybenzyl mercaptan (0.534 g, 2.81 mmol), 2-benzylsulfanylmethyl-acrylic acid (0.585 g, 2.81 mmol) and 4-dimethylaminopyridine (36 mg, 0.3 mmol) in DMF (1.5 ml) was stirred at room temperature for 20 hours. An additional amount of 2-difluoromethoxybenzyl mercaptan (0.201 g) was added to the reaction mixture and stirring was continued for another 24 hours. The reaction mixture was poured into dilute, cold, aqueous HCl and the product extracted with ethyl acetate. The extracts were washed with saturated aqueous sodium chloride and then dried over magnesium sulfate. The solvent was removed by rotary evaporation at reduced pressure and the residue was chromatographed on silica gel eluting with ethyl acetate/hexane to give 2-Benzylsulfanylmethyl-3-[2-(1,1-difluoro-methoxy)-benzylsulfanyl]-propionic acid (0.706 g).
