Reaction Steps
The obtained crude compound 7a (16.70 g, 24.89 mmol) was dissolved in MeOH (50 ml) and cooled down on an ice bath. NaOH (24 ml, 8M) solution was added dropwise to maintain the reaction temperature at 4° C. Then the pH of the reaction mixture was immediately adjusted to 7 by dropwise addition of HCl solution (2.3M). The organic layer was separated and washed with water, dried over anhydrous Na2SO4 and filtered. The filtrate was evaporated to dryness under reduced pressure. The residue was further purified by silica column chromatography using hexane-ethyl acetate from 60:40 to 0:100 with 10% increment as the eluent. The pure title compound (9.6 g, 67.7% yield) was obtained as a waxy solid with light yellow colour. 1H NMR(CDCl3): δ0.83, 0.85, 0.86, 0.88 (4s, 12H, CH3), 0.91 (d, 3H, J=6.1 Hz, CH3), 0.95-1.84 (m, 28H, CH2+CH+OH), 1.40 (d, 3H, J=6.4 Hz, H-5), 3.91 (t, 1H, H-3), 4.15-4.38 (m, 4H, COOCH2+H-2+H-4), 5.69 (d, 1H, J=4.2 Hz, H-1), 7.79 (br s, 1H, N—CH═C—F). MS (APCI): MW: 570.21. 13C NMR(CDCl3, 100 MHz): δ [19.64, 19.71, 22.59, 22.68, 24.27, 24.30, 24.45, 24.77, 27.93, 29.68, 32.76, 35.45, 35.54, 37.25, 37.30, 37.38, 37.42, 37.48, 39.33](CH3+CH2+CH+C5), 65.33 (OCH2), [74.94, 75.12 (br), 80.75](C2,C3,C4), 92.00 (br)(C1), 124.3-128.0 (br), 135.0-138.0 (br), 153.11 (NHCOO). Elemental Analysis: calculated: C, 63.24; H, 9.20; N, 7.38; F, 3.30. Found: C, 63.59; H, 9.32; N, 7.11; F, 3.29.
