A mixture of 4-(4-{[8-(2,6-dichloro-3,5-dimethoxy-phenyl)-quinoxaline-5-carbonyl]-amino}-phenyl)-piperazine-1-carboxylic acid tert-butyl ester (Step 8.1) (137 mg, 0.22 mmol) and a 4 N solution of HCl in dioxane (5 mL) was stirred for 1 h at rt. The reaction mixture was diluted with DCM and H2O. The aqueous layer was separated and extracted with DCM. The organic phase was washed with H2O and brine, dried (Na2SO4), filtered and concentrated. The residue was triturated in Et2O to afford 95 mg of the title compound as a red solid: ESI-MS: 537.9/539.9 [M+H]+; tR=4.01 min (System 1).
