of the reaction is monitored by means of tlc by which it is detected the disappearance of the starting product and the formation of drsp and 5 oh drsp as main products comparison with samples of the pure compounds obtained by methods known in the field the residue obtained by evaporation of the solvent is taken up with 100 ml of methylene chloride the solution is washed with water until ph gt 6 the ph of the aqueous phase of the first washing is about 4 then the solvent is eliminated under reduced pressure the product thus obtained after purification by chromatography 2 6 g is re checked by hplc that confirms the presence of drsp and 5 oh drsp the weight ratio between the two of 1 25 1 in favour of drsp is determined by chromatographing a homogeneous portion of the mixture and by weighing the two products isolated and dried to constant weight in addition a 100 mg sample of the mixture is oxidized as described in patent ep 0 075 189 example h a second 100 mg sample of the mixture is treated in thf with ptsa the products obtained by the two reactions are identified by means of hplc as drsp 5 g of crude triol ii 0 0128 mol are loaded into a 250 ml reactor for pressure reactions in 40 ml of thf and 80 ml of methylene chloride 253 44 mg of aqueous hydroxylamine solution at 50 0 00384 mol and 400 mg of tempo 0 00256 mol are added maintaining the temperature at 20 25 u00b0 c the system is brought to 6 bar with pure oxygen then heated at 80 u00b0.