Cl.[CH3:2][C:3]1[C:4]2[CH:12]=[CH:11][CH:10]=[CH:9][C:5]=2[S:6][C:7]=1[NH2:8].N1C=CC=CC=1.Cl[S:20]([C:23]1[CH:31]=[CH:30][C:26]([C:27]([OH:29])=[O:28])=[CH:25][CH:24]=1)(=[O:22])=[O:21]>C1COCC1.CCOC(C)=O>[CH3:2][C:3]1[C:4]2[CH:12]=[CH:11][CH:10]=[CH:9][C:5]=2[S:6][C:7]=1[NH:8][S:20]([C:23]1[CH:24]=[CH:25][C:26]([C:27]([OH:29])=[O:28])=[CH:30][CH:31]=1)(=[O:22])=[O:21]A 12-L 4-neck flask equipped with an overhead mechanical stirrer, N2 inlet/outlet adapter, and thermocouple was charged with THF (3.26 L) and compound 757-A (326 g, 1.6 mol) followed by pyridine (265 mL, 3.3 mol). The reaction mixture was cooled to 5° C. using a ice bath, to which was added a solution of 4-(chlorosulfonyl)benzoic acid (396 g, 1.8 mol) dissolved in THF (2.44 L), drop-wise. The reaction was allowed to stir at ambient temperature for 72 h, diluted with EtOAc (4 L), washed with 1N HCl (1 L), brine (1 L), the organic layer dried over Na2SO4, filtered and evaporated under reduced pressure. The crude residue was purified by triturating with EtOAc/heptane (1:1/1 L). The slurry was filtered, washed with heptane (2×250 mL) and dried in a vacuum oven at 40° C. for 18 h to afford 470 g of compound 306-C as a white solid. 1H-NMR (DMSO-d6): δ 13.51 (br s, 1H), 10.65 (br s, 1H), 8.12 (d, 2H), 7.86 (d, 2H), 7.83-7.79 (m, 1H), 7.66-7.63 (m, 1H), 7.37-7.33 (m, 1H), 2.03 (s, 3H).
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