To a solution of acetic acid (1R,2S,3S,4R,5S)-3,4-diacetoxy-1-acetoxymethyl-5-[4-chloro-3-(4-ethoxy-benzoyl)-phenyl]-6,8-dioxa-bicyclo[3.2.1]oct-2-yl ester (see Example 11 for preparation; 65 mg, 0.10 mmol) in methanol (3 mL) and tetrahydrofuran (2 mL) was added sodium methoxide in methanol (25% wt) until pH 12 was obtained and the resulting mixture was stirred at room temperature. After 16 hours, the reaction mixture was neutralized by the addition of Dowex Monosphere 650C (H) cation exchange resin until the pH of the solution was <7, filtered and concentrated under reduced pressure. The resulting material was precipitated from ethyl acetate and heptanes and the resulting white solid was washed with heptane 2 times and dried under reduced pressure to yield the desired product (44.5 mg, 94% yield). MS (LCMS) 451.1 (M+H+; positive mode) 1H NMR (400 MHz, METHANOL-d4) delta ppm 1.40 (t, J=6.9 Hz, 3 H), 3.55 (d, J=8.0 Hz, 1 H), 3.60 (d, J=7.4 Hz, 1 H), 3.65 (t, J=8.1 Hz, 1 H), 3.67 (d, J=12.5 Hz, 1 H), 3.77 (d, J=8.0 Hz, 1 H), 3.83 (d, J=12.5 Hz, 1 H), 4.12 (q, J=7.0 Hz, 2 H), 4.14 (d, J=7.6 Hz, 1 H), 6.98 (d, J=8.8 Hz, 2 H), 7.48 (d, J=8.4 Hz, 1 H), 7.52 (d, J=2.0 Hz, 1 H), 7.65 (dd, J=8.4, 2.0 Hz, 1 H), 7.73 (d, J=8.8 Hz, 2 H). HRMS calculated for C22H23O8Cl (M) 450.1081. found 450.1079.
