To a solution of the compound of step 1 (0.990 g, 1.61 mmol) in 11 ml of anhydrous THF, cooled to 0° C. under an atmosphere of nitrogen, was added a 1 M solution of lithium tri-tert-butoxy-aluminium hydride in THF. The mixture was stirred at 0-5° C. for 3.5 h. Then a 0.5 M aqueous solution of potassium hydrogensulfate (20 ml) was added, the mixture was vigorously stirred for 1 min and then extracted twice with EA (30 ml). The combined organic phases were washed with a saturated solution of sodium hydrogencarbonate (20 ml) and brine (40 ml), dried over magnesium sulfate and evaporated to dryness. The residue was purified by chromatography on silica gel (cyclohexane/EA, 70:30, then 65:35) to give 0.363 g of the title compound as a yellow solid melting at 208-209° C.
