The resulting Weinreb amide was dissolved in anhydrous THF (50 mL). The solution was cooled to -20 °C and methylmagnesium iodide (3.0 M in diethyl ether) (10.0 mL, 30.0 mmol) was added dropwise to the solution. After 1 h, the ice bath was removed and the mixture was allowed to warm up to room temperature overnight. Then, the solution was cooled to 0 °C and quenched with saturated NH4Cl (20 mL). The mixture was diluted with Et2O, the phases were separated and the organic phase was dried over Na2SO4, filtered and concentrated under vacuum. The product was used in the next step without further purification. Yield: 2.22 g (90%).