Compound A3

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InChIKey RHSMFOVCIJSUCM-WZMBSCFWSA-N

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

A12 (100.8 mg, 0.206 mmol) was dissolved in anhydrous dichloromethane (2 mL). Then sodium carbonate (122 mg, 1.15 mmol) was added to the solution and cooled to 0 °C. After cooling, a solution of peracetic acid (147 µL of a 32% by weight peracetic acid solution in dilute acetic acid, 0.618 mmol) was added dropwise to the reaction mixture. The reaction slowly warmed to room temperature over several hours and was quenched with a saturated solution sodium bicarbonate of after 19.5 hours. The reaction was then transferred to a separatory funnel and extracted with dichloromethane (3x). The organic layers were collected, dried with magnesium sulfate and concentrated under reduced pressure to give the crude product. The desired lactone was purified via column chromatography using 9:1 to 3:5 hexanes/ethyl acetate to give 46.8 mg (45% yield) A3 as a white foam in addition to 14.8 mg (15% yield) of starting material A12. ¹H NMR (CDCl₃, 500 MHz): δ 7.55 (dd, J = 7.9, 1.1 Hz, 1H), 7.39 (dd, J = 7.7, 1.7 Hz, 1H), 7.30 (td, J = 7.5, 1.2 Hz, 1H), 7.17 (td, J = 7.7, 1.8 Hz, 1H), 5.15 (m, 2H), 2.80 (ddd, J = 16.4, 6.9, 1.9 Hz, 1H), 2.68 - 2.40 (m, 7H), 2.34 - 2.18 (m, 3H), 2.16 - 2.06 (m, 2H), 2.05 - 1.92 (m, 2H), 1.70 - 1.61 (m, 1H), 1.63 (s, 3H), 1.58 - 1.44 (m, 1H), 0.84 (s, 3H). ¹³C NMR (CDCl₃, 125 MHz): δ 215.8, 207.6, 173.9, 173.0, 135.4, 133.0, 130.3, 129.9, 127.7, 123.7, 83.7, 66.1, 62.6, 50.7, 50.4, 50.3, 39.7, 36.7, 35.7, 35.4, 28.6, 27.1, 22.2, 22.0, 14.6. HRMS(ESI): m/z calc. for C₂₅H₃₀O₆Br [M+H]⁺: 505.1226, found: 505.1223.