To a solution of this silyi ether 24 (0.1 mmol) in benzotrifluoride (BTF, 4 mL) were added a nitro alkane (0.99 mmol), phenyl isocyanate (1.98 mmol) and two drops of triethylamine. The reaction mixture was stirred at 25° C for 3 days. After removal of the solvent, the residue was purified by three-phase extraction with FC-72 (20 mL), benzene (20 mL) and water (20 mL).The combined fluorous extracts were evaporated to yield the isoxazolines 25, which was dissolved in diethylether (3 mL) at 25° C. HF*pyridine (0.1 mL) was added and the solution was stirred for 1 h at 25° C. After removal of the solvent, the residue was dissolved in dichloromethane (20 mL). Saturated aqueous NH4CI (10 mL) was added and the organic-aqueous biphase was washed twice with FC-72 (10 mL). After separation of the layers, the aqueous phase was extracted twice with dichloromethane and the combined organic phases were dried (MgS04) and evaporated to yield the deprotected isoxa-zoline 26.
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