192704-56-6

209253-72-5

74-88-4

192704-56-6

Under stirring conditions, 5a (5 g, 12 mmol) was dissolved in DMF (40 ml) and heated to 45 °C. Subsequently, AcOH (2.9 ml, 51 mmol) was added to the solution. after 30 min, NaNO2 (2.484 g, 36 mmol) was added slowly in batches. After 1 hour of reaction, DMF (3 ml) solution of AcOH (2.9 ml, 51 mmol) was added dropwise. After 4 hours of reaction, the mixture was cooled to 0°C and quenched with saturated aqueous NaHCO3 solution. Na2SO3 solution (54 ml, 89 mmol) was added. The mixture was warmed to room temperature and stirred overnight. All solvent was removed under vacuum to give a powdered solid. The solid was diluted with acetone, filtered and the filter cake was washed three times with acetone. The organic layer was combined with the filtrate and concentrated to about 100 ml. To the concentrate was added MeI (1.5 ml, 24 mmol) and K2CO3 (5 g, 36 mmol) at 0 °C. The mixture was warmed to room temperature and stirred overnight. The reaction mixture was filtered and the filter cake was washed three times with DCM. The organic layer was combined with the filtrate and all solvents were removed under vacuum. The residue was diluted with DCM, washed sequentially with 10% aqueous HCl, aqueous NaHCO3 and brine, dried with Na2SO4, filtered and the filtrate was concentrated to give the crude product 6. The crude product can be purified by recrystallization from DCM/toluene to give colorless crystals 6 (4 g, 80% yield). The product characterization data were as follows: melting point 230-232 °C; 1H NMR (300 MHz, CDCl3) δ 5.68 (s, 1H), 4.04 (dt, J = 10.23, 9.84, 3.98 Hz, 1H), 3.64 (s, 3H), 2.85-2.71 (m, 2H), 2.68-2.18 (m, 8H), 2.10 -1.57 (m, 9H), 1.49-1.40 (m, 2H), 1.35 (s, 3H), 1.00 (s, 3H); HR-MS (EI) m/z C24H32O6 (M+) calculated value 416.221, measured value 416.225; Elemental analysis of the calculated value (C24H32O6): C 69.21, H 7.74; measured value C 68.32, H 7.72; UV maximum absorption wavelength 244nm.