反应详情

To a solution of (3R)-ethyl 2-(tert-butoxycarbonylamino)-3,5-dimethylnon-8-enoate (20 g, 0.061 moles) in THF/water (200 mL, 1:1) was added methanol (60.25 mL) followed by LiOH (7.7 g, 0.183 moles) at room temperature. The reaction mass was stirred at room temperature overnight. The solution was concentrated under reduced pressure and the residue was diluted with water (200 mL). The aqueous solution was acidified with aqueous 1.5 N HCl solution to pH˜3 and extracted with ethyl acetate (100 mL×3). The combined organic layers were dried over anhydrous Na2SO4 and concentrated under reduce pressure to get crude compound. The crude compound was purified by column chromatography (Silica gel, 3% methanol in DCM) to get 12.4 g (68%) of (3R)-2-(tert-butoxycarbonylamino)-3,5-dimethylnon-8-enoic acid as a gummy liquid. 1H NMR (400 MHz, DMSO-d6): δ ppm 12.4 (sb, 1H), 6.92-6.85 (m, 1H), 5.81-5.75 (m, 1H), 5.04-4.93 (m, 2H), 4.12-3.91 (m, 1H), 2.18-1.98 (m, 4H), 1.5 (s, 9H), 1.35-1.02 (m, 3H), 0.98-0.85 (m, 6H).

1. concentrationThe solution was concentrated under reduced pressure
2. additionthe residue was diluted with water (200 mL)
3. extractionextracted with ethyl acetate (100 mL×3)
4. dry with materialThe combined organic layers were dried over anhydrous Na2SO4
5. concentrationconcentrated
6. customto get crude compound
7. customThe crude compound was purified by column chromatography (Silica gel, 3% methanol in DCM)