[Cl:1][C:2]1[N:7]=[CH:6][C:5]([CH2:8][C@@H:9]([OH:12])[CH2:10][OH:11])=[CH:4][C:3]=1[F:13].O.[C:15]1(C)[CH:20]=CC(S(O)(=O)=O)=C[CH:16]=1>COC(OC)(C)C>[Cl:1][C:2]1[C:3]([F:13])=[CH:4][C:5]([CH2:8][C@@H:9]2[CH2:10][O:11][C:15]([CH3:20])([CH3:16])[O:12]2)=[CH:6][N:7]=1A suspension of 3 (2.50 g, 12.2 mmol) in dimethoxypropane (25 mL) was cooled with an ice bath and treated with paratoluene sulfonic acid monohydrate (0.23 g, 1.22 mmol). The ice bath was removed and the solution was stirred at room temperature for 16 hrs, cooled to 5° C. and treated with aqueous sat. NaHCO3 and extracted with ethyl acetate. The organic layer was separated, washed with brine, dried over sodium sulfate and concentrated to afford 2.90 g of 31 (97%) as an oil. 1HNMR (CDCl3) δ 1.34 (3 H, s), 1.42 (3 H, s), 2.87 (2 H, d, J=6.0 Hz), 3.62 (1 H, t, J=7.0 Hz), 4.08 (1 H, t, J=6.0 Hz), 4.30 (1 H, q, J=6.0 Hz), 7.46 (1 H, d, J=9.0 Hz), 8.12 (1 H, s). LC/MS (M+1) 247.
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