“…Compound 1a and 1b were synthesized starting from GS-441254 with reference to reported method. [26] 1 H NMR (500 MHz, DMSO- d 6 ) δ 8.26 (br, 1H), 7.96 (s, 1H), 7.10 (br, 1H), 6.99 (s, 1H), 6.25 (d, J = 6.1 Hz, 1H), 5.19 (d, J = 5.7 Hz, 1H), 4.93 (t, J = 5.7 Hz, 1H), 4.53 (t, J = 5.5 Hz, 1H), 4.06–4.00 (m, 1H), 3.96–3.88 (m, 1H), 3.69–3.61 (m, 1H), 3.54–3.45 (m, 1H). 13 C NMR (126 MHz, DMSO- d 6 ) δ 154.91, 148.42, 124.07, 116.77, 112.09, 110.30, 102.84, 84.87, 78.01, 74.68, 69.60, 60.25.MS m/z = 326.0 [M+1] + .…”