The combine organic layers were washed with 1 M NaHCO3 (3 × 15 mL) and brine . Then, the collected organic layers were dried over anhydrous MgSO4, filtered and concentrated under vacuum. The obtained residue was purified by flash column chromatography on silica gel (3:1 to 1:1 pentane/ethyl acetate) to yield the desired product.