Reaction Steps
To a solution of 7 (125 mg, 0.261 mmol) in anhydrous N,N-dimethylformamide (7 mL) was added sodium azide (169 mg, 2.61 mmol). The reaction mixture was heated to 65° C. and stirred overnight. Excess sodium azide was filtered off and the solvent was removed by rotary evaporation. The crude residue was dissolved in ethyl acetate and washed with water three times. The organic layer was dried over sodium sulfate and concentrated followed by flash chromatography in hexanes/ethyl acetate (2:1) to give 9 (78 mg, 68%). 1H NMR (500 MHz, CD3OD) δ 5.61 (d, J=4.9 Hz, 1H), 3.39 (t, J=6.4 Hz, 2H), 3.25-3.17 (m, 4H), 2.60 (t, J=9.1 Hz, 1H), 2.45-2.33 (m, 2H), 2.25-2.15 (m, 2H), 2.12-2.03 (m, 1H), 1.99 (m, 1H), 1.89-1.76 (m, 2H), 1.70-1.29 (m, 15H), 1.29-1.15 (m, 2H), 1.13 (d, J=11.0 Hz, 4H), 1.04-0.87 (m, 2H), 0.60 (s, 3H). 13C NMR (125 MHz, CD3OD) δ 210.81, 202.29, 174.92, 124.24, 78.00, 72.34, 62.71, 59.71, 57.39, 55.16, 52.43, 45.67, 39.99, 39.72, 36.81, 34.72, 33.90, 33.20, 30.15, 29.75, 25.52, 24.46, 24.17, 23.76, 22.15, 17.67, 13.96. ESI-MS m/z [M+Na]+ observed: 464.2, calculated: 464.3.
