Reaction Steps
Anhydrous DMSO (3.28 g, 41.94 mmol) in dry DCM (20 mL) was added dropwise over 5 minutes to a stirred solution of oxalyl chloride (10.48 mL of a 2 N solution in DCM, 20.97 mmol) under a nitrogen atmosphere at −50° C. After stirring for 5 minutess, a solution 7 (5.90 g, 13.98 mmol), in dry DCM (45 mL) was added dropwise over 45 minutes to the reaction mixture, which was then stirred for a further 45 minutes at −50° C. TEA (9.89 g; 97.87 mmol) was added dropwise to the mixture over 15 minutes followed by stirring for a further 15 minutes. The reaction mixture was left to warm to room temperature, diluted with H2O (150 mL) and DCM (100 mL). The organic phase was washed with 1 N HCl (2×100 mL), water (2×100 mL), brine (2×100 mL) and dried over MgS evaporation afforded the crude product (8), which was purified by flash column chromatography using 50:50 petroleum ether (40-60°):EtOAc as eluent. Evaporation of the pure fractions in vacuo afforded the product (4.33 g, 10.3 mmol, 74%). 1HNMR (270 MHz, CDCl3) δ 7.30 (s, 1H, ArH), 7.24 (s, 1H, ArH), 5.60 (d, 1H, J=9.89 Hz, SEM amino acetal CH2), 4.69 (d, 1H, J=9.89 Hz, SEM amino acetal CH2), 4.62 (dd, 1H, J=9.89, 3.12 Hz, 11a), 4.26-4.19 (m, 1H, 3), 3.95 (s, 3HOHe), 3.94 (s, 3H, OMe), 3.81-3.49(m, 4H, SEM 1=CH2+1+3), 2.82-2.71 (m, 1H, 1), 0.95 (t, 2H, J=2.01 Hz, SEM 2=CH2), −0.04 (s, 9H, SEM CH3); 13C NMR (67.8 MHz, CDCl3) δ206.8, 168.8, 165.9, 152.4, 147.5, 134.0, 120.4, 111.1, 105.6, 78.2, 67.2, 56.2, 54.8, 52.3, 37.3, 18.3, −1.3.
