[4-(2-Amino-5-thiophen-2-yl-phenylcarbamoyl)-benzyl]-phosphonic acid dimethyl ester (35 mg, 0.066 mmol) was made 0.25 M in dioxane and to this stirring solution was added 5N aqueous sodium hydroxide (26 μL, 0.132 mmol). The resulting solution was stirred at 80° C. overnight then diluted with DMF, acidified with TFA, and purified by HPLC (0-60% MeCN in water w/0.025% TFA) to afford the title compound: 1H NMR (DMSO-d6, 600 MHz) δ9.80 (s, 1H), 7.91 (d, J=8.4 Hz, 2H), 7.48-7.50 (m, 1H), 7.31-7.42 (m, 4H), 7.26-7.28 (m, 1H), 7.04-7.06 (m, 1H), 6.88 (d, J=8.4 Hz, 1H), 3.52 (d, J=11.4 Hz, 3H), 3.18 (d, J=21.6 Hz, 2H). MS: cal'd 403 (MH+), exp 403 (MH+)
