To a solution of 1 (1.5 g,3.5mmol) in CH2Cl2 (10 mL) at 22-24oC wasadded 3,4- dihydro-2H-pyran (0.479 mL, 0.442 g, 5.25mmol) and PPTs (20 mg, 0.08mmol). The solution wasstirred at 22-24oC for 1 h and diluted with a 100-mL solution of(1:1) diethyl ether and ethyl acetate. The organic layer was separated, washed with H2O(3 ´ 100mL), and the residuewas chromatographed, eluting with hexane/ethyl acetate (20:1) to give the THPether 2 as clear oil (1.75 g, 97%).
To an ethanol solution (30 mL) of THP ether 1 (1.87 g, 5mmol) was added PPTS (20 mg,0.08mmol) in one portion. The solution was refluxed for 1 h, cooled to 22-24oC,and diluted with a mixture of diethyl ether (100 mL) and H2O (200mL). The organic layer was washed with H2O (2 ´ 100mL), dried over Na2SO4and concentrated in vacuo. The residue was purified by chromatography onsilica gel, eluting with hexane/ethyl acetate (3:1) to give 2 (1.36 g, 94%) as clear oil.