The procedure for the preparation of [2-(3-cyclopropyl-2,4-dioxo-3,4-dihydro-2H-quinazolin-1-ylmethyl)-1-(3-methyl-butyl)-1H-benzoimidazol-5-ylmethyl]-carbamic acid tert-butyl ester was followed starting with 3-vinyl-1H-indazole (140 mg, 0.970 mmol) and 2,2-dimethyl-propionic acid 4-[5-(tert-butoxycarbonylamino-methyl)-2-chloromethyl-benzoimidazol-1-yl]-butyl ester; HCl salt (474 mg, 0.614 mmol). After quenching with water, a gum formed. The water was decanted and the residue partitioned between diethyl ether and water. The layers were separated and the aqueous phase extracted with diethyl ether (2×40 mL). The combined organic phases were washed with water (twice), brine, and dried (MgSO4). Purification by flash chromatography (eluent hexane-acetone 2:3) afforded 2,2-dimethyl-propionic acid 4-[5-(tert-butoxycarbonylamino-methyl)-2-(3-vinyl-indazol-1-ylmethyl)-benzoimidazol-1-yl]-butyl ester (386 mg, 71%) as a colorless foam:
