[C:1]([NH:4][C@H:5]([CH2:10][C:11]1[CH:16]=[CH:15][C:14]([O:17][CH2:18][CH:19]=[CH2:20])=[CH:13][CH:12]=1)[C:6]([O:8]C)=[O:7])(=[O:3])[CH3:2].O.[OH-].[Li+]>C1COCC1.O.O>[C:1]([NH:4][C@H:5]([CH2:10][C:11]1[CH:16]=[CH:15][C:14]([O:17][CH2:18][CH:19]=[CH2:20])=[CH:13][CH:12]=1)[C:6]([OH:8])=[O:7])(=[O:3])[CH3:2]To a solution of 52 (900 mg, 3.25 mmol) in THF/water, 3:1 (10 mL) was added lithium hydroxide monohydrate (273 mg, 6.5 mmol), and the resulting suspension was allowed to stir for 16 h. The reaction mixture was diluted with water (30 mL) and the THF was removed in vacuo. The aqueous layer was extracted with diethyl ether (40 mL) to remove unreacted starting material. The aqueous phase was acidified with 10% HCl and the resulting precipitate was extracted with DCM (3×40 mL). The combined DCM fractions were dried and evaporated to yield the title compound (750 mg, 2.85 mmol, 88%) as a white solid. [α]D23 −23.2 (c. 0.1, EtOH). Mp 75° C. 1HNMR (D6 acetone, 300 MHz): δ 7.27 (d, J=7.8 Hz, 1H, NH); 7.17 (d, J=8.7 Hz, 2H, ArH2′ and ArH6′); 6.86 (d, J=8.7 Hz, 21H, ArH3′ and ArH5′); 6.06 (m, 1H, H2″); 5.40 (dd J=1.5 Hz, 17.5 Hz, 1H, H3a″); 5.23 (dd, J=1.5, 10.5 Hz, 1H, H3b″); 4.67 (dd, J=5.1, 8.1, 10.5 Hz 1H, H2); 4.53 (d, J=5.1 Hz, 2H, H1″); 3.11 (dd, J=5.4, 14.1 Hz, 1H; 3Ha); 2.93 (dd, J=8.1, 14.1, 1H, 3Hb); 1.89 (s, 31H, NCOCH3). Mass Spectrum (CI, +ve) m/z 264 (100%) [MH+]. HRMS calcd for C14H18NO4 264.123583, found 264.123770.
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