Sodium Hydroxide → Tert-butoxy[4-(2-hydroxy-4-methylphenyl)-2-methyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridin-3-yl]acetic acid

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To a stirred solution of the major diastereoisomeric pair of ethyl tert-butoxy[4-(2-hydroxy-4-methylphenyl)-2-methyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridin-3-yl]acetate (Step 9, 214 mg, 458 μmol) in ethanol (5 mL) and tetrahydrofuran (5 mL) was added a solution of sodium hydroxide (2 N, aqueous, 2 mL, 2.75 mmol) and the reaction was stirred at 60° C. for 18 hours. The reaction was concentrated in vacuo until all organic solvents had been removed, the aqueous residue was then acidified with hydrochloric acid (2 N, aqueous) to pH 2. The precipitated solid was collected by filtration and washed with tert-butyl methyl ether (10 mL) and dried in vacuo to give a mixture of diastereoisomers of the title compound as a white solid, 76 mg, in a 38% yield. LC-MS (12 min acidic) 5.51 mins 81% pure by UV, ES+/APCI+ 440, ES−/APCI− 438. 1H NMR (400 MHz, CDCl3) δ ppm 1.04 (s, 9 H) 1.66-1.88 (m, 4 H) 2.09-2.21 (m, 2 H) 2.40 (s, 3 H) 2.73 (s, 3 H) 2.82 (t, 2 H) 5.33 (s, 1 H) 6.78 (s, 1 H) 6.85 (d, 1 H) 7.36 (d, 1 H).

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