Sodium hydride (60% dispersion in mineral oil, 0.113 g, 2.82 mmol) was added to a solution of the product from Example 1, Step F (0.80 g, 2.35 mmol) in anhydrous DMF (50 mL) under nitrogen. After 20 min, the reaction mixture was cooled (ice bath), 1,4-dibromo-2-butene (0.754 g, 3.53 mmol) was added and the mixture stirred for 2 h. Morpholine (5 mL) was added and the reaction mixture was stirred at ambient temperature for 18 h. DMF was evaporated under reduced pressure and the residue was mixed with a saturated solution of sodium bicarbonate (100 mL) and extracted with ethyl acetate (2×100 mL). The combined extracts were dried (MgSO4), filtered and evaporated to dryness. Chromatography on silica (ethyl acetate) gave the desired product as a viscous oil (0.65 g, 58%).
