Compound 105 (1.14 g, 4.49 mmol) was dissolved in 4 mL dichloromethane. Triethylamine (681.4 mg, 6.73 mmol) was added to this solution. The reaction mixture was cooled with an ice bath and trifluoroacetic anhydride (1.41 g, 6.73 mmol) was added in a dropwise manner. The reaction mixture was stirred at 0° C. for 30 minutes and then 3-phthalimidylpropanol (106) (2.4 g, 13.26 mmol) was added. The reaction mixture was warmed to room temperature and stirred at room temperature for 2 hours. The reaction was quenched with saturated aqueous NaHCO3 solution and extracted with ethyl acetate. The organic layer was washed with water and saturated NaCl solution, dried over MgSO4, filtered and evaporated in vacuo to an oil which was purified by column chromatography (silica, 2:1 hexane/ethyl acetate) (107: 522 mg (trans); 108: 271 mg (cis); 1:1 mixture of 107 and 108: 110 mg; total yield 46%) . 1H NMR (CDCl3): 107: 1.70 (m,1H); 1.82 (m,1H); 2.00(m,2H); 2.02(m,1H); 2.28(m,1H); 3.46(m,1H); 3.83(s,3H); 3.84(m,3H); 3.88(s,6H); 4.99(t,1H); 5.30(dd,1H); 6.56(s,2H); 7.72(m,2H); 7.85(m,2H). 108: 1.95(m,3H); 2.00(m,2H); 2.20(m,1H); 3.51(m,1H); 3.83(s,3H); 3.85(m,2H); 3.88(s,6H); 3.92(m,1H); 4.90(m,1H); 5.16(dd,1H); 6.60(s,2H); 7.72(m,2H); 7.84(m,2H).
