To a solution of the product from Example 5, Step 3 (720 mg, 3.24 mmol) in DMF (9 mL) was added triphenylphosphine (850 mg, 3.24 mmol). The reaction solution was kept at ambient temperature for 1 hour and a solution of 2-(4-hydroxybutylamino)pyridine N-oxide (590 mg, 3.24 mmol) and diethyl azodicarboxylate (0.51 mL, 3.24 mmol) in DMF (5 mL) was added. The reaction solution was kept at room temperature for 18 hours and concentrated in vacuo. The residue was dissolved in ethyl acetate and washed with water. The aqueous solution was back extracted with ethyl acetate. The combined organic solution was washed with brine, dried (Na2SO4) and concentrated in vacuo. The residue was purified by chromatography (98:1:1 CH2Cl2:MeOH:NH4OH) to give the desired product, (560 mg, 45% yield).
