Hydrochloric Acid → 4-[4'-(1,3-Benzothiazol-2-ylamino)-1,1'-biphenyl-4-yl]-2,2-dimethyl-4-oxobutanoic acid

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In a 8-mL screw-cap vial, a mixture of methyl 4-(4′-amino-1,1′-biphenyl-4-yl)-2,2-dimethyl-4-oxobutanoate (60 mg, 0.19 mmol) and 2-chloro-1,3-benzothiazole (40 mg, 0.23 mmol) in 3 mL n-butanol were heated at 90° C. overnight. The formation of methyl 4-[4′-(1,3-benzothiazol-2-ylamino)-1,1′-biphenyl-4-yl]-2,2-dimethyl-4-oxobutanoate was monitored by LC-MS. The solvent was removed under reduced pressure. The residue was dissolved in 2 mL tetrahydrofuran/dioxane (1:1), and 3 equivalents of 1 N aqueous sodium hydroxide was added to the solution. The mixture was shaken at rt overnight and then at 50° C. for 2 h. The progress of the hydrolysis reaction was monitored by LC-MS. A solution of 1N aqueous HCl (3.1 equivalents) was then added to the mixture, and the solvent was removed under reduced pressure. The residue was redissolved in 2 mL methanol and a minimum amount of DMF, and the product was isolated and purified by preparative reverse-phase HPLC (water/acetonitrile gradient, containing 0.1% TFA) to give 40 mg of 4-[4′-(1,3-benzothiazol-2-ylamino)-1,1′-biphenyl-4-yl]-2,2-dimethyl-4-oxobutanoic acid (Yield: 45%). 1H NMR (400 MHz, DMSO-d6) δ 11.90 (bs, 1H), 10.65 (s, 1H), 8.00 (d, 2H), 7.90 (d, 2H), 7.80 (m, 5H), 7.60 (d, 1H), 7.35 (t, 1H), 7.20 (t, 1H), 3.30 (s, 2H), 110 (s, 6H); LC-MS m/z 431.2 (MH+), ret. time 3.40 min.

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