反应详情

To the crude product of step K (110 mg, 0.22 mmol) in methanol (5 mL) and water (5 mL) at 0° C. was added lithium hydroxide monohydrate (92 mg, 2.2 mmol). The solution was stirred at ambient temperature for 2 h then concentrated in vacuo. Water (10 mL) was added and the mixture extracted with ethyl acetate (3×10 mL). The combined organic extracts were dried over Na2SO4, filtered, and concentrated in vacuo to give the crude product. Purification by flash column chromatography (SiO2, 9:1 to 7:3, hexanes/ethyl acetate) afforded tert-butyl 6-chloro-3-(hydroxymethyl)-8-(phenylsulfonyl)-3,4-dihydrobenzofuro[3,2-c]pyridine-2(1H)-carboxylate (85 mg, 80%) as a colorless oil: 1H NMR (CDCl3, 300 MHz) δ 7.98-7.95 (m, 3H), 7.84 (d, J=1.5 Hz, 1H), 7.56-7.51 (m, 3H), 4.93 (br s, 2H), 4.13-4.10 (m, 1H), 3.64-3.61 (m, 2H), 3.17-3.08 (m, 1H), 2.88 (d, J=17.4 Hz, 1H), 1.85 (br s, 1H), 1.53 (s, 9H).

1. concentrationthen concentrated in vacuo
2. additionWater (10 mL) was added
3. extractionthe mixture extracted with ethyl acetate (3×10 mL)
4. dry with materialThe combined organic extracts were dried over Na2SO4
5. filtrationfiltered
6. concentrationconcentrated in vacuo
7. customto give the crude product
8. customPurification by flash column chromatography (SiO2, 9:1 to 7:3, hexanes/ethyl acetate)