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DOI: 10.1055/s-2004-830889
A Brief Total Synthesis of Eupolauramine
Publication History
Publication Date:
04 August 2004 (online)
Abstract
A concise synthesis of the alkaloid eupolauramine has been achieved. The key step was a benzotriazolyl-mediated connection of a bromoaryl unit to the azaisoindolinone framework by an enol ether function. Free radical cyclization then provided the natural product.
Key words
alkaloids - carbanions - enols - ring closure - total synthesis
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References
All new compounds have been fully characterized. 1H NMR (300 MHz, CDCl3), 13C NMR and APT spectral data (75 MHz, CDCl3) and elemental analysis of the key intermediates for Compound 10: white solid, mp 176-177 °C. 1H NMR: δ = 1.12 (s, 9 H, 3 CH3), 2.83 (s, 3 H, NCH3), 5.89 (d, J = 8.3 Hz, 1 H, ArH), 6.15 (d, J = 7.8 Hz, 1 H, ArH), 6.81 (t, J = 7.8 Hz, 1 H, ArH), 7.06 (t, J = 6.8 Hz, 1 H, ArH), 7.17 (t, J = 7.8 Hz, 1 H, ArH), 7.24-7.36 (m, 2 H, ArH + CHOC=O), 7.55 (d, J = 8.3 Hz, 1 H, ArH), 7.76 (d, J = 4.8 Hz, 1 H, ArH), 8.11-8.14 (m, 1 H, ArH), 9.05 (d, J = 4.8 Hz, 1 H, ArH), 9.17 (s, 1 H, ArH). 13C NMR: δ = 27.0 (3 CH3), 27.9 (CH3), 38.6 (C), 74.4 (CH), 83.4 (C), 109.9 (CH), 117.7 (CH), 122.0 (CH), 124.8 (CH), 125.6 (C), 126.8 (CH), 128.6 (CH), 128.7 (CH), 130.8 (CH), 131.4 (C), 132.5 (C), 133.8 (CH), 135.6 (C), 140.7 (C), 145.6 (CH), 146.6 (C), 151.1 (CH), 165.1 (C), 175.7 (C). Anal. Calcd for C26H24BrN5O3 (534.42): C, 58.44; H 4.53; N, 13.10. Found: C, 58.79; H, 4.84; N, 13.37. Compound Z-3: white solid, mp 169-170 °C. 1H NMR: δ = 1.25 (s, 9 H, 3 CH3), 3.55 (s, 3 H, NCH3), 7.25-7.47 (m, 3 H, ArH), 7.64-7.76 (m, 3 H, ArH), 8.64 (d, J = 4.9 Hz, 1 H, ArH). 13C NMR: δ = 26.8 (3 CH3), 29.4 (CH3), 39.3 (C), 116.8 (CH), 124.5 (C), 127.4 (C), 127.9 (CH), 130.0 (C), 131.8 (C), 132.0 (CH), 133.7 (CH), 134.3 (C), 134.4 (CH), 135.8 (C), 143.9 (CH), 149.3 (CH), 165.4 (C), 176.4 (C). Anal. Calcd for C20H19BrN2O3 (415.29): C, 57.84; H, 4.61; N, 6.75. Found: C, 57.61; H, 4.54; N, 6.47.