The operation is carried out as in Stage 2 of Example 7 starting from 141 mg of the product obtained in Stage 1 of Example 7, 2 ml of methanol, 0.7 ml (15 eq) of benzaldehyde and 0.1 ml of acetic acid then the reaction medium is agitated at ambient temperature for approximately 3 hours. Then 55 mg of sodium cyanoborohydride (NaBH3CN) is added and the reaction medium is agitated at ambient temperature for 1 hour. 10 ml AcOEt is added, followed by washing with 2×5 ml H2O, then 5 ml of a saturated aqueous solution of NaCl, drying and evaporating the solvent. After purification by chromatography on silica eluting with methylene chloride/ethyl acetate in a proportion of 70/30, the product obtained is impasted in hexane and in this way 143 mg of expected product is obtained.
