p-Toluenesulfonic acid → HCID 57033897, compound

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Reaction Steps

The difluoroester (5) (880 mg, 1.9 mmol) was treated with 2% KOH-MeOH (30 ml) at room temperature for 2 hr. The usual work-up (ether for extraction) gave a crude acid. This in ether (10 ml) was treated with ethereal solution of diazomethane until the gas evolution was ceased. This solution was concentrated under reduced pressure to leave the residue. This in dioxane (10 ml) was treated with 2,3-dihydropyran (516 μl) and TsOH (10 mg) at room temperature for 3 hr. The usual work-up (ether for extraction) gave a crude product, which was applied to a column of silica gel (200 g). Elution with n-hexane-ether (15:1) provided the THP-ester (6) (907 mg, 95%), amorphous. 1H-NMR δ: 0.70 (3H, s, 18-H3), 1.03 (3H, s, 19-H3), 1.10 (3H, d, J=6 Hz, 21-H3), 3.53 (2H, m, THP), 3.86 (3H, s, --CO2CH3), 3.93 (1H, m, 3-H), 4.73 (1H, m, THP), 5.36 (1H, m, 6-H). 19F-NMR δ: +40.0. MS m/z: 424 (M+ -DHP), 406, 391.

Provenance & Evidence