A solution of dichloromethane (5 mL), compound 23 (45 mg, 0.168 mmol) and triethylamine (71 μL, 0.509 mmol) was cooled to 0° C. 2-chloro-1-ethane sulfonyl chloride (16 μL, 0.148 mmol) was added and the reaction was allowed to proceed for 1 hour prior to addition of saturated sodium bicarbonate (10 mL) and extraction with dichloromethane (2×10 mL). The combined organic layers were dried with MgSO4, filtered and concentrated in vacuo. The product was purified by preparative RP-HPLC and lyophilized (8.7 mg, 16% yield): 1H NMR (400 MHz, DMSO) δ 10.30 (s, 1H), 8.36 (s, 1H), 7.60 (d, J=8.5, 2H), 7.31 (d, J=8.6, 2H), 6.86 (dd, J=16.4, 9.9, 1H), 6.21 (d, J=16.4, 1H), 6.09 (d, J=9.9, 1H), 5.08 (hept, J=6.7, 2H), 1.49 (d, J=6.7, 6H); 13C NMR (100 MHz, DMSO) δ 155.44, 152.03, 151.64, 144.22, 138.54, 136.17, 129.25, 127.98, 127.41, 119.52, 96.95, 48.66, 21.75; [M+H]+ calculated for C16H18N6O2S 359.1, found 359.5.
