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Synlett 2005(3): 417-420  
DOI: 10.1055/s-2004-837222
LETTER
© Georg Thieme Verlag Stuttgart · New York

The Total Synthesis of Pygmaeocin C

Chin-Long China, Duong Duc-Phi Tranb, Kak-Shan Shiaa,b, Hsing-Jang Liu*a,b
a Department of Chemistry, National Tsing Hua University Hsinchu, Taiwan 30013, P. R. China
b Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
Fax: +886-3-5720711; e-Mail: hjliu@mx.nthu.edu.tw;
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Publication History

Received 1 November 2004
Publication Date:
22 December 2004 (online)

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Abstract

Making use of a recently developed intramolecular Friedel-Crafts alkylation process as the key operation, the first total synthesis, in racemic form, of pygmaeocin C has been achieved.

Key words

pygmaeocin C - total synthesis - intramolecular Friedel-Crafts alkylation

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Compound 2: IR (neat): 2973, 2847, 2746, 1729, 1705, 1465, 1384, 1300, 1253, 1205, 1185, 1144 cm-1. 1H NMR (400 MHz, CDCl3): δ = 9.92 (t, J = 3.2 Hz, 1 H), 2.56-2.24 (m, 2 H), 2.36 (t, J = 3.2 Hz, 2 H), 2.31 (d, J = 14.4 Hz, 1 H), 2.16 (d, J = 14.4 Hz, 1 H), 1.94-1.89 (m, 2 H), 1.28 (s, 3 H), 0.93 (s, 6 H). 13C NMR (100 MHz, CDCl3): δ = 210.1 (C=O), 202.8 (CHO), 51.8 (CH2), 48.8 (CH2), 41.1 (C), 38.1 (C), 37.5 (CH2), 33.7 (CH2), 24.0 (2 × CH3), 20.1 (CH3). HRMS (EI): m/z (%) = 182.1305 (5) [M+] (calcd for C11H18O2: 182.1307), 138.1036 (100, calcd for C9H14O: 138.1045), 123.0801 (69, calcd for C8H11O: 123.0810).

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Compound 3: IR (neat): 2963, 2936, 1588, 1574, 1481, 1464, 1429, 1411, 1334, 1294, 1219, 1172, 1058, 1008 cm-1. 1H NMR (400 MHz, CDCl3): δ = 6.93 (d, J = 2.2 Hz, 1 H), 6.85 (d, J = 2.2 Hz, 1 H), 3.81 (s, 3 H), 3.76 (s, 3 H), 3.29 (sep, J = 6.8 Hz, 1 H), 1.17 (d, J = 6.8 Hz, 6 H). 13C NMR (100 MHz, CDCl3): δ = 153.2 (C), 145.4 (C), 144.0 (C), 121.3 (CH), 116.4 (C), 113.1 (C), 60.7 (CH3), 55.7 (CH3), 26.7 (CH), 23.2 (2 × CH3). HRMS (EI): m/z (%) = 258.0245 (1) [M+] (calcd for C11H15BrO2: 258.0255), 180.9873 (100, calcd for C5H10BrO2: 180.9864).

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Compound 19: IR (neat): 2963, 2874, 1744, 1716, 1690, 1580, 1487, 1463, 1318, 1280, 1234, 1148, 1067, 1010 cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.27 (s, 1 H), 6.77 (d, J = 1.6 Hz, 1 H), 6.73 (d, J = 1.6 Hz, 1 H), 6.26 (d, J = 16.4 Hz, 1 H), 6.06 (d, J = 16.4 Hz, 1 H), 3.84 (s, 3 H), 3.80 (s, 3 H), 3.77 (s, 3 H), 3.29 (sep, J = 6.8 Hz, 1 H), 2.58 (d, J = 16.0 Hz, 1 H), 2.22 (d, J = 16.0 Hz, 1 H), 1.33 (s, 3 H), 1.18 (d, J = 6.8 Hz, 6 H), 1.01 (s, 3 H), 0.99 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 194.7 (C), 164.7 (C), 161.1 (CH), 152.6 (C), 146.3 (C), 142.4 (C), 132.2 (C), 131.2 (CH), 130.3 (C), 129.4 (CH), 117.0 (CH), 107.1 (CH), 60.8 (CH3), 55.6 (CH3), 52.1 (CH3), 50.0 (CH2), 45.8 (C), 39.1 (C), 26.7 (CH), 24.7 (CH3), 24.1 (CH3), 23.3 (2 × CH3), 20.3 (CH3). HRMS (EI): m/z (%) = 400.2243 (60) [M+] (calcd for C24H32O5: 400.2250), 369.2062 (20, calcd for C23H29O4: 369.2066), 316.1677 (100, calcd for C19H24O4: 316.1675), 301.1456 (34, calcd for C18H21O4: 301.1440).

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(±)-Pygmaeocin C: IR (neat): 3369, 2966, 2934, 2873, 1627, 1574, 1440, 1337, 1307, 1292, 1264, 1131, 1037 cm-1. 1H NMR (600 MHz, CDCl3): δ = 7.95 (br s, 1 H), 7.05 (s, 1 H), 6.53 (s, 1 H), 6.35 (d, J = 9.7 Hz, 1 H), 5.90 (d, J = 9.7 Hz, 1 H), 3.26 (sep, J = 6.8 Hz, 1 H), 2.66 (d, J = 17.0 Hz, 1 H), 2.14 (d, J = 17.0 Hz, 1 H), 1.24 (d, J = 6.8 Hz, 3 H), 1.22 (s, 3 H), 1.21 (d, J = 6.8 Hz, 3 H), 1.16 (s, 3 H), 0.93 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 201.0 (C), 163.0 (C), 144.5 (C), 142.1 (C), 138.5 (C), 130.5 (CH), 127.2 (C), 125.6 (CH), 124.1 (CH), 116.6 (CH), 114.8 (C), 48.3 (CH2), 45.3 (C), 38.8 (C), 27.3 (CH), 26.1 (CH3), 24.3 (CH3), 22.5 (CH3), 22.2 (CH3), 21.3 (CH3). HRMS (EI): m/z (%) = 312.1724 (14) [M+] (calcd for C20H24O3: 312.1725), 294.1626 (16, calcd for C20H22O2: 294.1620), 256.1094 (55, calcd for C16H16O3: 256.1099), 228.1148 (100, calcd for C15H16O2: 228.1150), 213.0916 (28, calcd for C14H13O2: 213.0916).