Compound 23

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Compound data: 1H NMR

Compound data: 13C NMR

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

To a 250 mL round-bottomed flask was added bis-allylic alcohol S4 (see Supplementary information) (2.94 g, 5.39 mmol), tetrabutylammonium iodide (200 mg, 5.40 mmol), iPr₂NEt (7.00 mL, 40.5 mmol), and CH₂Cl₂ (30 mL). The solution was cooled to 0 °C and 2-(trimethylsilyl)ethoxymethyl chloride (2.67 mL, 21.6 mmol) was added dropwise over 5 min. The resulting mixture was then heated to 40 °C and held at this temperature. After 2 h, the solution was allowed to cool to room temperature, poured into a separatory funnel, and washed with sat. NH₄Cl aq. (10 mL). The aqueous phase was extracted with CH₂Cl₂ (10 mL × 2). The combined organic layers were washed with brine (10 mL), dried over MgSO₄, filtered and concentrated under reduced pressure. The crude residue was purified by column chromatography (SiO₂, 5% to 15% EtOAc/ hexanes) to provide SEM ether 23 (3.19 g, 88%) as a pale yellow oil of 1:1 mixture of diastereomers. Note: Analytical data represents a 1:1 mixture of diastereomers. R_f: 0.75 (25% EtOAc/ hexanes); ¹H NMR (600 MHz, CDCl₃): δ 7.88–7.86 (m, 4H), 7.62–7.59 (m, 2H), 7.54–7.51 (m, 4H), 5.90 (br s, 2H), 5.31–5.29 (m, 3H), 5.28 (s, 1H), 5.24 (dd, J = 8.7, 1.5 Hz, 1H), 5.12–5.07 (m, 2H), 5.07 (s, 1H), 5.04 (s, 1H), 4.62 (d, J = 6.9 Hz, 1H), 4.61 (d, J = 6.9 Hz, 1H), 4.57 (d, J = 6.9 Hz, 1H), 4.55 (d, J = 6.9 Hz, 1H), 3.97 (s, 4H), 3.64–3.52 (m, 4H), 3.35 (d, J = 14.4 Hz, 1H), 3.32 (d, J = 14.4 Hz, 1H), 2.89 (d, J = 14.4 Hz, 1H), 2.85 (d, J = 14.4 Hz, 1H), 2.77–2.71 (m, 2H), 2.52 (br, 2H), 2.09–1.97 (m, 10H), 1.69 (d, J = 1.2 Hz, 3H), 1.67 (d, J = 1.2 Hz, 3H), 1.55 (s, 3H), 1.54 (s, 3H), 1.49 (s, 3H), 1.47 (s, 3H), 0.904 (s, 9H), 0.900 (s, 9H), 0.82 (d, J = 7.4 Hz, 6H), 0.054 (s, 6H), 0.050 (s, 6H), –0.01 (s, 9H), –0.02 (s, 9H); ¹³C NMR (151 MHz, CDCl₃): δ 145.7, 145.3, 142.32, 142.26, 139.99, 139.94, 135.2, 134.83, 134.80, 134.75, 133.45, 133.42, 129.33, 129.32, 127.62, 127.56, 126.6, 125.00, 124.97, 124.8, 124.18, 124.15, 111.7, 111.4, 91.8, 91.7, 73.4, 71.7, 68.82, 68.78, 65.46, 65.44, 64.7, 64.6, 43.28, 43.25, 39.48, 39.45, 33.9, 33.6, 31.52, 31.45, 26.3, 26.2, 26.1, 23.1, 23.0, 18.6, 18.33, 18.30, 16.8, 16.7, 16.1, 16.0, 13.6, –1.30, –5.10 (Five ¹³C signals are overlapping with others); HRMS (ESI): Calc’d for C₃₈H₆₄O₅NaSSi₂ [M+Na]⁺: 711.3905, found: 711.3896.