To a solution of 18 or 26–29 in anhydrous DMF (conc. 0.13 M) was successively added 17 (1.10 eq), KI (0.30 eq) and K2CO3 (3.00 eq). After stirring for 24 h at 50 °C under argon, the reaction was diluted in AcOEt and water. The aqueous layer was extracted with AcOEt and the combined organic extracts were washed with brine, dried over Na2SO4 and concentrated under vacuum. The residue was purified by flash column chromatography (silica gel, linear gradient 0–8% MeOH in DCM) to give the desired compound as colored solid.