Download PDF
Synlett 2007(15): 2371-2374  
DOI: 10.1055/s-2007-986634
LETTER
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Total Synthesis of the Sesquiterpene (±)-β-Isocomene

Arndt W. Schmidt, Thomas Olpp, Elke Baum, Tina Stiffel, 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;
Further Information

Publication History

Received 20 June 2007
Publication Date:
28 August 2007 (online)

    Permissions and Reprints All articles of this category

Abstract

Application of the Lewis acid mediated [3+2] cycloaddition of allyl-tert-butyldiphenylsilane combined with a modified Fleming-Tamao oxidation provides a stereoselective route to the triquinane sesquiterpene (±)-β-isocomene.

Key words

cycloadditions - Lewis acids - silicon - stereoselective synthesis - terpenoids

17

Characteristic Spectroscopic Data of 10, 11, (±)-1, and (±)-2:
Compound 10: colorless crystals, mp 112 °C. 13C NMR and DEPT (125 MHz, CDCl3): δ = 18.60 (C), 19.83 (CH3), 21.64 (CH), 23.23 (CH2), 23.72 (CH3), 28.47 (3 CH3), 35.46 (CH2), 40.17 (CH2), 43.21 (CH2), 44.92 (CH2), 45.83 (C), 53.14 (CH2), 59.61 (C), 62.43 (C), 127.48 (4 CH), 129.11 (2 CH), 133.76 (C), 134.12 (C), 136.47 (2 CH), 136.53 (2 CH), 223.74 (C=O). Anal. Calcd (%) for C29H38OSi: C, 80.87; H, 8.89. Found: C, 80.64; H, 8.26.
Compound 11: colorless oil. 13C NMR and DEPT (125 MHz, CDCl3): δ = 21.12 (CH3), 22.96 (CH2), 23.00 (CH3), 35.58 (CH2), 41.29 (CH2), 45.48 (CH2), 46.23 (C), 49.07 (CH2), 50.19 (CH2), 57.46 (C), 61.44 (C), 71.76 (CH), 223.43 (C=O).
(±)-β-Isocomene [(±)-1]: colorless crystals, mp 76-82 °C. IR (ATR): ν = 3073, 2925, 2869, 2854, 1655, 1460, 1376, 1260, 1106, 1024, 878 cm-1. 1H NMR (500 MHz, CD2Cl2): δ = 0.92 (d, J = 7.0 Hz, 3 H), 0.99 (s, 3 H), 1.10 (s, 3 H), 1.22-1.68 (m, 10 H), 2.00 (m, 1 H), 2.10 (d, J = 14.4 Hz, 1 H), 2.34 (dt, J = 14.4, 2.4 Hz, 1 H), 4.60 (m, 1 H), 4.63 (m, 1 H). 13C NMR and DEPT (125 MHz, CD2Cl2): δ = 18.08 (CH3), 23.53 (CH3), 24.27 (CH3), 24.33 (CH2), 30.55 (CH2), 34.87 (CH2), 40.83 (CH), 41.95 (CH2), 43.15 (CH2), 48.23 (CH2), 49.68 (C), 55.14 (C), 67.01 (C), 100.79 (CH2), 162.76 (C). MS (EI): m/z (%) = 204 (21) [M+], 189 (68), 175 (12), 162 (15), 161 (35), 149 (22), 148 (29), 147 (49), 134 (28), 133 (42), 122 (29), 121 (44), 120 (31), 119 (40), 109 (68), 108 (100), 107 (60). Anal. Calcd (%): for C15H24O: C, 88.16; H, 11.84. Found: C, 88.27; H, 11.98.
(±)-Isocomene [(±)-2]: colorless oil. IR (ATR): ν = 3020, 2927, 2866, 2853, 1672, 1458, 1443, 1375, 1002, 940, 845 cm-1. 1H NMR (500 MHz, CDCl3): δ = 0.85 (d, J = 7.2 Hz, 3 H), 1.026 (s, 3 H), 1.030 (s, 3 H), 1.14-1.43 (m, 5 H), 1.48-1.58 (m, 4 H), 1.55 (d, J = 1.3 Hz, 3 H), 1.70-1.73 (m, 1 H), 1.99 (m, 1 H), 4.85 (m, 1 H). 13C NMR and DEPT (125 MHz, CDCl3): δ = 13.00 (CH3), 17.27 (CH3), 23.16 (CH3), 23.71 (CH3), 24.01 (CH2), 31.91 (CH2), 33.62 (CH2), 37.22 (CH2), 39.88 (CH), 42.60 (CH2), 56.61 (C), 59.86 (C), 63.75 (C), 132.66 (CH), 142.81 (C). MS (EI): m/z (%) = 204 (10) [M+], 189 (16), 175 (7), 162 (100), 161 (17), 147 (49), 134 (18), 133 (19), 119 (31), 105 (20), 91 (18). Anal. Calcd (%) for C15H24O: C, 88.16; H, 11.84. Found: C, 88.20; H, 11.80.

18

Crystal data for 10: C29H38OSi, crystal size: 0.60 × 0.40 × 0.40 mm3, M r = 430.68 g mol-1, monoclinic, space group P21/c, λ = 0.71073 Å, a = 13.4071(14), b = 12.1653(9), c = 16.2492(17) Å, β = 109.414(11)°, V = 2499.6(4) Å3, Z = 4, ρ calcd = 1.144 g cm-3, µ = 0.112 mm-1, T = 200(2) K, θ range = 2.14°-25.85°; reflections collected: 18979, independent: 4787 (R int = 0.0393). The structure was solved by direct methods and refined by full-matrix least-squares on F 2; R 1 = 0.0481, wR 2 = 0.1275 [I > 2σ(I)]; maximal residual electron density: 0.424 e Å-3. CCDC 646230 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.

22

Ratio of compound 15/monoalkylated isomer 1/monoalkylated isomer 2/dialkylated product 1/dialkylated product 2 = 78.2:14.0:3.6:2.2:2.0.