[OH-].[K+].C([O:5][C:6](=[O:28])[C:7]([CH3:27])([CH3:26])[CH2:8][CH2:9][CH2:10][CH2:11][CH:12]([OH:25])[CH2:13][CH2:14][CH2:15][CH2:16][C:17]([CH3:24])([CH3:23])[C:18]([O:20]CC)=[O:19])C>O.C(O)C>[OH:25][CH:12]([CH2:13][CH2:14][CH2:15][CH2:16][C:17]([CH3:24])([CH3:23])[C:18]([OH:20])=[O:19])[CH2:11][CH2:10][CH2:9][CH2:8][C:7]([CH3:27])([CH3:26])[C:6]([OH:28])=[O:5]To a homogeneous solution of potassium hydroxide (3.45 g, 61 mmol) in water (3.3 mL) and ethanol (11.1 mL) was added 7-hydroxy-2,2,12,12-tetramethyltridecanedioic acid diethyl ester (8.2 g, 22 mmol) and the mixture was heated at reflux for 4 h. The mixture was concentrated in vacuo and the residue was extracted with diethyl ether (3×50 mL). The water layer was acidified with concentrated hydrochloric acid (6 mL) to pH 1. The product was extracted with diethyl ether (3′100 mL). The combined organic layers were dried over sodium sulfate and concentrated in vacuo. The crude product was purified by column chromatography (silica, dichloromethane:methanol=90:10) to give the pure product (6.6 g, 95%) as a colorless oil. 1H NMR (300 MHz, CDCl3/TMS): δ (ppm): 8.10 (br., 3H), 3.58 (br., 1H), 1.62-1.22 (m, 16H), 1.18 (s, 12H). 13C NMR (75 MHz, CDCl3/TMS): δ (ppm): 184.3, 71.8, 42.1, 40.5, 36.9, 25.9, 25.0, 24.9. HRMS (LSIMS, gly): Calcd. for C17H33O5 (MH+): 317.2328. found 317.2330. HPLC: 90.4% purity.
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