[CH2:1]([Li])CCC.[CH3:6][O:7][C:8]1[C:17]2[C:12](=[CH:13][CH:14]=[CH:15][CH:16]=2)[C:11]([O:18][CH3:19])=[CH:10][C:9]=1[CH2:20][OH:21].CI.O>C1COCC1>[CH3:6][O:7][C:8]1[C:17]2[C:12](=[CH:13][CH:14]=[CH:15][CH:16]=2)[C:11]([O:18][CH3:19])=[C:10]([CH3:1])[C:9]=1[CH2:20][OH:21]n-Butyllithium (7.3 mL, 18.3 mmol, 2.5 M in hexanes) was added dropwise via syringe to a solution of 23a (1.00 g, 4.58 mmol) in THF (30 mL) at −78° C. under argon. The solution was slowly warmed to room temperature and stirred for 1 h. Methyl iodide (0.34 mL, 5.50 mmol) was added dropwise and the solution was stirred for 20 min. Water (8 mL) was added and the mixture was extracted with EtOAc (4×). The combined organic layers were dried (MgSO4), filtered and evaporated. Column chromatography of the crude product (45:55 EtOAc:hexanes) afforded 23b (0.61 g, 57%) as a yellow solid; Rf=0.59 (45:55 EtOAc:hexanes); mp=116-117° C.; lit mp=118-121° C.25; 1H NMR (CDCl3): δ 8.07 (dd, 2H), 7.51 (m, 2H), 4.94 (s, 2H), 3.98 (s, 3H), 3.88 (s, 3H), 2.52 (s, 3H), 1.73 (bs, 1H).
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