out for 1 hour reaction check in hplc reaction ended residual compound iv less than 1 stirring is continued for 1 h repeating the hplc check a solution of 28 ml acetic acid in 3 5 l water is added to the reaction mixture after which extraction is carried out with ethyl acetate 1 l three times the solvent is distilled under reduced pressure at 45 u00b0 c yielding 54 g of crude compound v yellow oil 50 g of crude compound v are dissolved in 40 ml methylene chloride 60 ml heptane is added and methylene chloride is distilled at atmospheric pressure it is cooled to 0 5 u00b0 c filtering the resulting solid after drying at 50 u00b0 c for 12 hours 40 8 g of compound v are obtained the analyses of the compound give results corresponding to the product in example 3 7 g of compound iv are suspended in a solution obtained by mixing 167 ml thf and 233 ml methanol at t 20 22 u00b0 c 8 19 g cecl 3 7h 2 o and 770 mg nabh 4 are added by spontaneous exothermy the reaction mixture reaches 27 u00b0 c stirring is continued for 45 minutes letting the temperature drop to 20 25 u00b0 c a solution of 4 ml acetic acid in 500 ml water is added to the reaction mixture extraction is carried out with ethyl acetate 100 ml three times after distillation of the solvent.