To a solution of 5-bromo-N-(4-fluorobenzyl)-8-hydroxy-1,6-naphthyridine-7-carboxamide from example 126 (45 mg, 0.120 mmol), N-methylpiperazine (79.8 ul, 0.72 mmol) in DMPU (0.50 ml) was heated at 135 C for 18 hrs. The resulting mixture was treated with TFA (100 ul) and purified by preparative HPLC (Gilson Semi Preparative HPLC System and a YMC Combiprep Pro Column (50×20 mm i.d., C18, S-5 um, 120A) eluting with 5-95% acetonitrile/water (0.1%) at 15 ml/min) to afford the piperazin-4-ium trifluoroacetate salt of the title compound after lyophillization.
