To a stirred solution of triethyleneglycol monomethyl ether (9.5 mL, 61 mmol) at 0°C in dry dichloromethane (15 mL) and pyridine (3.5 mL), phosphorous tribromide (3.8 mL, 41 mmol) was added. The solution was allowed to stir at room temperature 16 h. The mixture was filtered through Whatman filter paper, extracted with 100 mL aqueous saturated sodium carbonate solution, 50 mL 5% sulfuric acid, and deionized water twice. The organic phase was dried over MgSO4, filtered through cotton and dried to yield the yellow crude product 1.