C([C@@H]1COC(=O)N1[C:14]([C@H:16]1[C:18]2([CH2:23][CH2:22][O:21][CH2:20][CH2:19]2)[CH2:17]1)=[O:15])C1C=CC=CC=1.[OH-].[Li+].OO.S([O-])([O-])(=[O:30])=S.[Na+].[Na+]>O1CCCC1.O>[C@H:16]1([C:14]([OH:15])=[O:30])[C:18]2([CH2:23][CH2:22][O:21][CH2:20][CH2:19]2)[CH2:17]1A solution of 3.700 g of (R)-4-benzyl-3-((R)-6-oxaspiro[2.5]-octane-1-carbonyl)oxazolidin-2-one in 20 ml of tetrahydrofuran/water 3:1 is cooled to 0° C. 0.608 g of lithium hydroxide and 1.95 ml of hydrogen peroxide (30% in water) are added to the solution, which is stirred at room temperature for 6 hours. Saturated aqueous sodium thiosulphate solution is added to the reaction mixture, which is then extracted with tert-butyl methyl ether. The aqueous phase is adjusted to pH 2 with 4M HCl and extracted with dichloromethane. The combined extracts are washed with brine, dried with sodium sulphate and evaporated. The title compound is obtained as a colourless liquid and is employed without further purification for the next stage. Rf=0.55 (dichloromethane-methanol-water-acetic acid 150:54:10:1); Rt=2.10 (Gradient I).
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