A solution of the acid chloride of 4-benzyloxybenzoic acid (2.56 g, 10.4 mmol) in dichloromethane (30 mL) and dimethylformamide (5 mL) was added dropwise to a solution of compound 4 (2.23 g, 10.4 mmol) and triethylamine (2.4 mL, 17.2 mmol) in dichloromethane (15 mL). After 1.5 h, 4-dimethylaminopyridine (0.12 g) was added. The reaction was stirred at rt for 18 h and then heated to 45° C. for 4 h. The reaction was cooled to rt and then extracted with 1 N KHSO4 (1×) and brine (1×). The organic layer was dried (MgSO4) and concentrated on a rotary evaporator. The residue was purified by column chromatography (silica gel, 10-20% ethyl acetate/hexanes (v/v)) to afford compound 11 as a slightly purple solid (2.08 g, 47%). ESI-MS m/e 426.3 (M+1).
