To a solution of 4-(2-(5-amino-8-methylbenzo[f][1,7]naphthyridin-2-yl)ethyl)phenol (from Example 170) (1.0 equiv.) in dimethylformamide (0.10 M) 22° C. was added 60% dispersion of sodium hydride in mineral oil (1.5 equiv.) and the resulting mixture was allowed to stir for 30 min At this point, ethyl 5-bromopentanoate (1.2 equiv.) was added to this mixture. The reaction mixture was then allowed to stir for 18 hours. after which it was diluted with ethyl acetate and water. The biphasic layers were separated and the organic layer was washed twice with water. The organic layer was dried over anhydrous Na2SO4 and the volatiles were removed in vacuo. The resulting residue was purified by RP-HPLC using a 10-50% MeCN in water gradient. The resulting trifluoroacetate salt was then converted to the free base form by utilizing a StratoSpheres™ PL-SO3H SPE ion exchange resin, delivering ethyl 5-(4-(2-(5-amino-8-methylbenzo[f][1,7]naphthyridin-2-yl)ethyl)phenoxy)pentanoate as a solid. 1H NMR (Acetone-d6): δ 8.80 (s, 1H), 8.74 (s, 1H), 8.33 (d, 1H), 7.47 (s, 1H), 7.24 (d, 1H), 7.17 (d, 2H), 6.85 (d, 2H), 4.10 (q, 2H), 3.97 (t, 2H), 3.25 (t, 2H), 3.07 (t, 2), 2.50 (s, 3H), 2.37 (t, 3H), 1.74-1.84 (m, 4H), 1.21 (t, 3H). LRMS [M+H]=458.2
