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According to the method described for the synthesis of 207d, 206g (36.0 g, 161 mmol) was treated with 3,4-dihydro-2H-pyran (18.5 g, 220 mmol) and p-toluenesulfonic acid hydrate (0.28 g, 1.5 mmol) in CH2Cl2 (60 mL). After filtration through neutral aluminum oxide (200 g) and concentration, the crude product was purified by column chromatography (silica gel; hexanes/ethyl acetate=50/1), affording 207g (23.0 g, 46%) as an oil. 1H NMR (CDCl3): δ 4.54 (t, 1H, J=3.0), 3.84 (m, 1H), 3.51-3.39 (m, 4H), 2.98 (d, 1H, J=9.3), 1.89-1.80 (m, 3H), 1.70-1.40 (m, 7H), 1.29-1.22 (m, 4H), 0.89 (s, 6H). 13C NMR (CDCl3): δ 99.3, 76.6, 62.1, 39.3, 34.3, 34.2, 33.0, 30.8, 29.2, 25.7, 24.7, 23.2, 19.6. HRMS (LSIMS, gly): Calcd for C14H28BrO2 (MH+): 307.1272, found: 307.1245.

1. filtrationAfter filtration
2. concentrationthrough neutral aluminum oxide (200 g) and concentration
3. customthe crude product was purified by column chromatography (silica gel; hexanes/ethyl acetate=50/1)