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Synlett 2007(10): 1549-1552  
DOI: 10.1055/s-2007-982535
LETTER
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Total Synthesis of the Sesquiterpene (±)-Cameroonanol

Arndt W. Schmidt, Thomas Olpp, Sören Schmid, Sigrid Goutal, Anne Jäger, Hans-Joachim Knölker*
Department Chemie, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany
Fax: +49(351)46337030; e-Mail: hans-joachim.knoelker@tu-dresden.de;
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Publication History

Received 12 April 2007
Publication Date:
06 June 2007 (online)

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Abstract

We describe a stereoselective synthesis of the triquinane (±)-cameroonanol using the Lewis acid mediated [3+2] cyclo­addition of an allylsilane and a modified Fleming-Tamao oxidation as key steps.

Key words

cycloadditions - Lewis acids - silicon - stereoselective synthesis - terpenoids

    References and Notes

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12

Characteristic Spectroscopic Data of the Triquinanes 7, 11-14 and 1
Compound anti-7: colorless oil. 13C NMR and DEPT (125 MHz, CDCl3): δ = 18.57 (C), 24.55 (CH3), 25.35 (CH), 27.34 (CH3), 27.87 (CH3), 28.47 (3 CH3), 29.45 (CH2), 35.57 (CH2), 38.36 (CH2), 40.01 (CH2), 44.94 (C), 47.21 (C), 48.03 (CH2), 55.03 (CH), 70.98 (C), 127.28 (2 CH), 127.36 (2 CH), 128.88 (2 CH), 134.32 (C), 134.44 (C), 136.54 (2 CH), 136.56 (2 CH), 229.55 (C=O).
syn-7: colorless oil. 13C NMR and DEPT (125 MHz, CDCl3): δ = 18.04 (C), 22.31 (CH3), 26.37 (CH3), 26.89 (CH2), 28.47 (3 CH3), 28.60 (CH), 29.83 (CH3), 30.64 (CH2), 31.19 (CH2), 41.75 (CH2), 45.16 (C), 45.56 (CH), 46.70 (CH2), 48.90 (C), 68.11 (C), 127.45 (2 CH), 134.82 (C), 135.29 (C), 136.13 (2 CH), 136.25 (2 CH), 136.54 (2 CH), 136.56 (2 CH), 223.41 (C=O).
Compound 11: colorless oil. 13C NMR and DEPT (125 MHz, CDCl3): δ = 25.59 (CH3), 27.13 (2 CH3), 31.07 (CH2), 41.69 (CH2), 43.49 (CH2), 43.92 (CH2), 45.61 (C), 46.52 (CH), 47.35 (C), 49.76 (CH2), 66.86 (C), 217.06 (C=O), 225.86 (C=O).
Compound 12: colorless oil. 13C NMR and DEPT (125 MHz, CDCl3): δ = 14.90 (CH3), 25.84 (CH3), 26.25 (CH3), 26.99 (CH3), 29.04 (CH2), 42.31 (CH2), 44.07 (CH2), 46.04 (C), 46.26 (C), 49.10 (CH), 50.18 (CH2), 55.85 (CH), 64.41 (C), 218.76 (C=O), 226.94 (C=O).
Compound 13: colorless crystals, mp 84 °C. 13C NMR and DEPT (125 MHz, CDCl3): δ = 13.69 (CH3), 25.27 (CH3), 25.74 (CH2), 26.78 (CH2), 27.11 (CH3), 27.52 (CH3), 28.02 (CH2), 28.79 (CH2), 40.29 (CH2), 44.29 (C), 47.14 (CH2), 47.80 (C), 49.16 (CH2), 52.47 (CH), 58.69 (CH), 60.77 (C), 68.16 (C), 225.62 (C=O). Anal. Calcd (%) for C18H28OS2: C, 66.61; H, 8.70; S, 19.76. Found: C, 66.60; H, 8.48; S, 19.68.
Compound 14: colorless oil. 13C NMR and DEPT (125 MHz, CDCl3): δ = 18.83 (CH3), 24.60 (CH3), 27.38 (CH3), 27.70 (CH3), 28.81 (CH2), 31.71 (CH2), 36.58 (CH2), 40.83 (CH2), 43.26 (CH), 44.97 (C), 47.62 (C), 48.37 (CH2), 61.17 (CH), 70.67 (C), 229.19 (C=O).
(±)-Cameroonanol [(±)-1]: colorless crystals, mp 42-45 °C. IR (ATR): ν = 3604, 3479, 2929, 2864, 1458, 1374, 1242, 1163, 1077, 1051, 997, 976, 910, 782, 667 cm-1. 1H NMR (500 MHz, CDCl3): δ = 0.90 (s, 3 H), 0.96 (s, 3 H), 0.99 (d, J = 6.6 Hz, 3 H), 1.03 (s, 3 H), 1.18-1.27 (m, 1 H), 1.30-1.34 (m, 1 H), 1.38-1.45 (m, 3 H), 1.50-1.67 (m, 5 H), 1.73-1.81 (m, 1 H), 1.90 (t, J = 8.2 Hz, 1 H), 3.68 (br s, 1 H). 13C NMR and DEPT (125 MHz, CDCl3): δ = 19.37 (CH3), 23.79 (CH3), 25.67 (CH3), 28.99 (CH2), 32.45 (CH3), 35.33 (CH2), 36.11 (CH2), 38.64 (C), 39.97 (CH2), 43.82 (CH), 47.56 (C), 51.36 (CH), 52.60 (CH2), 67.10 (C), 89.71 (CH). MS (EI): m/z (%) = 222 (7), 207 (11), 204 (39), 189 (27), 176 (13), 166 (40), 148 (50), 135 (100), 124 (49), 109 (24), 96 (41), 95 (36), 93 (29), 81 (32). HRMS: m/z calcd for C15H26O: 222.1984; found: 222.1971. Anal. Calcd (%) for C15H26O: C, 81.02; H, 11.79. Found: C, 81.05; H, 11.74.
(±)-epi-Cameroonanol [(±)-epi-1]: colorless oil. 1H NMR (500 MHz, CDCl3): δ = 0.81 (s, 3 H), 0.91 (d, J = 6.6 Hz, 3 H), 0.96 (s, 3 H), 1.03 (s, 3 H), 1.19-1.88 (m, 12 H), 3.35 (br s, 1 H). 13C NMR and DEPT (125 MHz, CDCl3): δ = 19.01 (CH3), 21.49 (CH3), 25.66 (CH2), 26.40 (CH2), 28.44 (CH3), 28.51 (CH3), 36.75 (CH2), 38.13 (CH), 41.75 (C), 43.48 (CH2), 48.36 (C), 52.71 (CH2), 62.73 (CH), 65.70 (C), 88.24 (CH). GC-MS (EI): m/z (%) = 222 (8), 204 (41), 189 (27), 175 (34), 166 (55), 148 (42), 135 (100), 124 (46), 119 (37), 107 (40), 95 (40), 93 (40), 91 (53), 79 (45).

13

Crystal Data for anti -10
C18H32O3Si, crystal size: 0.51 × 0.47 × 0.08 mm3, M r = 324.53 g mol-1, triclinic, space group P1bar, λ = 0.71073 Å, a = 12.186 (3) Å, b = 15.114 (1) Å, c = 16.730 (4) Å, α = 103.50 (1)°, β = 95.17 (2)°, γ = 104.16 (1)°, V = 2869.5 (10) Å3, Z = 6, ρ calcd = 1.127 g cm-3, µ = 0.133 mm-1, T = 198 (2) K, θ range = 3.52-22.50°; reflections collected: 43390, independent: 7450 (R int = 0.0522). The structure was solved by direct methods and refined by full-matrix least-squares on F 2; R 1 = 0.0407, wR 2 = 0.1006 [I > 2σ(I)]; maximal residual electron density: 0.464 e Å-3. CCDC 636590 contains the supplementary crystallographic data for this structure. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

18

Crystal Data for 13
C18H28OS2, crystal size: 0.46 × 0.34 × 0.28 mm3, M r = 324.52 g mol-1, triclinic, space group P1bar, λ = 0.71073 Å, a = 7.486 (2) Å, b = 9.117 (2) Å, c = 13.246 (3) Å, α = 85.58 (3)°, β = 77.34 (3)°, γ = 87.08 (3)°, V = 878.9 (4) Å3, Z = 2, ρ calcd = 1.226 g cm-3, µ = 0.301 mm-1, T = 198 (2) K, θ range = 3.52-25.41°; reflections collected: 11484, independent: 3126 (R int = 0.0295). The structure was solved by direct methods and refined by full-matrix least-squares on F 2; R 1 = 0.0351, wR 2 = 0.0769 [I > 2σ(I)]; maximal residual electron density: 0.273 e Å-3. CCDC 636591 contains the supplementary crystallographic data for this structure. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.