To a solution of 5.3 g of the product obtained in Step A (13.9 mmol) in 278 mL of tetrahydrofuran there are added 14 mL of BH3Me2S (27.8 mmol) at ambient temperature. The whole is heated for 4 hours at 80° C. It is allowed to return to ambient temperature, and then there are added 7 mL (14 mmol) of BH3Me2S. The reaction mixture is again heated at 80° C. for 2 hours. The tetrahydrofuran is subsequently evaporated off, and there are then added slowly methanol and then 5.6 mL of 5N hydrochloric acid (27.8 mmol). The mixture is stirred at ambient temperature overnight and then at 80° C. for one hour. There is subsequently added a saturated NaHCO3 solution to the reaction mixture at 0° C. until a pH of 8 is reached, and then extraction with ethyl acetate is carried out. The organic phase is subsequently dried over magnesium sulphate and then filtered and evaporated to dryness. The title product is obtained in the form of an oil.
