A mixture of (R)—N-[(1R,2R)-3-[[(1,1-dimethylethyl)diphenylsilyl]oxy]-2-methyl-1-phenylpropyl]-2-methyl-2-propanesulfinamide (Example 136b, 5.2 g), methanol (25 mL) and a solution of hydrogen chloride in 1,4-dioxane (4M, 25 mL) was stirred at 50° C. for 7 h and left at room temperature for 70 h. The mixture was concentrated in vacuo and the residue was washed with ether to give the crude amine hydrochloride (2.0 g). 3-(3,5-Dibromo-2-oxo-2H-pyrazin-1-yl)-4-methyl-benzoic acid, methyl ester (Example 1b, 3.5 g) was added followed by N,N-diisopropylethylamine (4 mL) and tetrahydrofuran (50 mL). The mixture was stirred at 50° C. for 24 h. After cooling to room temperature, the mixture was diluted with ethyl acetate (200 mL) and washed with sat. aqueous NaHCO3. The organic phase was dried (Na2SO4), filtered and concentrated in vacuo. Ethanol (50 mL) was added under nitrogen atmosphere followed by wet palladium on carbon (10%, 227 mg), ammonium formate (3 g) and N,N-diisopropylethylamine (2 mL). The mixture was stirred at 70° C. for 2 h, cooled to room temperature, filtered through a pad of Celite and concentrated in vacuo. The residue was diluted with ethyl acetate (200 mL) and washed with water. The organic phase was dried (Na2SO4), filtered and concentrated in vacuo to give the subtitle compound (3.5 g).
