852821-06-8

856906-36-0

69739-34-0

852821-06-8

2,6-Dimethylpyridine (75.0 μL, 0.640 mmol, 5.0 eq.) and tert-butyldimethylsilyl trifluoromethanesulfonate (88.0 μL, 0.380 mmol, 3.0 eq.) were sequentially added to a solution of (4AS,8aS,9S)-3-(phenylmethoxy)-9-(dimethylamino)-8a,9-dihydronaphtho[2,3-d]isoxazole-4. 5(4aH,8H)-dione (47.0 mg, 0.130 mmol, 1.0 equiv) in a solution of dichloromethane (3 mL). The reaction mixture was stirred at 23 °C for 3 hours. Subsequently, it was quenched by addition of aqueous potassium phosphate buffer solution (pH 7.0, 0.2 M, 15 mL). The reaction mixture was extracted with dichloromethane (2 x 20 mL), the organic phases were combined and dried over anhydrous sodium sulfate. The dried organic phase was filtered and the filtrate was concentrated to give (4AS,8aS,9S)-3-(benzyloxy)-4a-((tert-butyldimethylsilyl)oxy)-9-(dimethylamino)-8a,9-dihydronaphthaleno[2,3-d]isoxazole-4,5(4aH,8H)-dione (56.0 mg, 91% yield) as a white crystalline solid. Melting point: 157-158°C (decomposition); Thin layer chromatography Rf value: 0.54 (ethyl acetate:hexane = 1:3); 1H NMR (500 MHz, CDCl3) δ 7.51 (d, 2H, J = 1.5 Hz, ArH), 7.50-7.34 (m, 3H, ArH), 6.94 (m, 1H, =CHCH2), 6.10 ( ddd, 1H, J = 10.3, 1.5, 1.5 Hz, =CHC(O)), 5.36 (m, 2H, OCH2Ar), 3.79 (d, 1H, J = 10.7 Hz, CHN(CH3)2), 2.83 (m, 2H, =CCH2), 2.78 (m, 1H, C3CH), 2.46 (s, 6H, N(CH3) 2), 0.84 (s, 9H, C(CH3)3), 0.27 (s, 3H, SiCH3), 0.06 (s, 3H, SiCH3); 13C NMR (125 MHz, CDCl3) δ 193.4, 187.9, 181.6, 167.7, 149.5, 135.2, 128.8, 128.8, 128.8 , 128.6, 108.6, 83.5, 72.8, 59.8, 48.1, 42.2, 26.3, 25.8, 19.3, -2.2, -3.8; FTIR (neat, cm-1) 2942 (s), 1719 (s, C=O), 1678 (s, C=O), 1602 (m), 1510 (s), 1053 (s, C-O), 733 (s); HRMS (ES) m/z calculated value (C26H34N2O5Si + H)+ 483.2315, measured value 483.2321.