Lithium Hydroxide → 2-[4-(Ethoxy-hydroxy-phosphoryl)-but-2-enyl]-6-(4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydro-isobenzofuran-5-yl)-4-methyl-hex-4-enoic acid

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A mixture of 2-[4-(diethoxy-phosphoryl)-but-2-enyl]-6-(4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydro-isobenzofuran-5-yl)-4-methyl-hex-4-enoic acid methyl ester 4C (25 mg, 0.048 mmol) and lithium hydroxide (200 mg) in a mixture of methanol (3 mL) and water (1 mL) was stirred at 70° C. for 2 hours. The organic solvent was evaporated and the residue acidified with 2N HCl and extracted with ethyl acetate/acetonitrile. The organic extract was concentrated, and the residue was purified by preparative reverse-phase HPLC (acetonitrile and 0.1% aqueous CF3COOH), affording 2-[4-(ethoxy-hydroxy-phosphoryl)-but-2-enyl]-6-(4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydro-isobenzofuran-5-yl)-4-methyl-hex-4-enoic acid 4E as an oil (15 mg, 89%); 1H NMR (300 MHz, CD3OD) δ 1.25 (t, J=6.9 Hz, 3H), 1.81 (s, 3H), 2.1-2.6 (m, 8H), 3.40 (d, J=6.6 Hz, 2H), 3.77 (s, 3H), 3.97 (m, 2H), 5.1-5.3 (m, 3H), 5.67 (brs, 2H) ppm.

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