Hydrochloric Acid → 4-{3E-[4-(1-Carboxy-1-methyl-ethoxy)-2-methoxy-5-thiophen-2-yl-phenyl]-acryloyl}-benzoic acid

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2-(4-Formyl-5-methoxy-2-thiophen-2-yl-phenoxy)-2-methyl-propionic acid (Ex-47, 0.23 g, 0.72 mmol) and 4-acetylbenzoic acid (0.12 g, 0.72 mmol) were dissolved in a dimethylformamide-methanol solution (5 mL, 7:3). After complete dissolution, lithium methoxide (0.11 g, 2.9 mmol) was added and the resulting orange slurry was stirred in the dark at room temperature for 4 h. Upon completion, as determined by HPLC, the mixture was diluted with water (15 mL), acidified with a 1 N hydrochloric acid solution, and extracted with ethyl acetate (4×25 mL). The combined organic extracts were dried over sodium sulfate and evaporated to dryness. The crude oil was taken up in a tetrahydrofuran-heptane solution (5 mL, 10:1) and warmed to 60° C. to obtain complete dissolution and allowed to cool to room temperature. The resulting precipitate was collected on filter paper and dried in vacuo to yield 0.30 g (90%) of the title compound as a dark yellow solid, mp 135–137° C. 1H-NMR (300 MHz, DMSO-d6) δ 8.32 (s, 1H), 8.23 (d, 2H, J=8.4 Hz), 8.10 (d, 2H, J=8.4 Hz), 7.99 (d, 2H, J=15.6 Hz), 7.71 (d, 1H, J=3.0 Hz), 7.54 (d, 1H, J=5.1 Hz), 7.14 (dd, 1H, J=5.1, 3.0 Hz), 6.49 (s, 1H), 3.85 (s, 3H), 1.69 (s, 6H). MS (ESI) m/z=467 ([M+H]+, 100%). Anal. Calcd. for C25H28O8S.EtOH: C, 63.27; H, 5.51; S, 6.26. Found: C, 63.40; H, 5.19; S, 6.38.

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