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Synlett 2008(15): 2368-2372  
DOI: 10.1055/s-2008-1078266
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Convergent Synthesis of the A-J Ring System of Yessotoxin

Kohei Torikai, Koji Watanabe, Hiroaki Minato, Tomoyoshi Imaizumi, Michio Murata, Tohru Oishi*
Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
Fax: +81(6)68505775; e-Mail: oishi@chem.sci.osaka-u.ac.jp;
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Publication History

Received 24 May 2008
Publication Date:
21 August 2008 (online)

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Abstract

A highly convergent synthesis of the A-J ring system of yessotoxin was achieved. A convergent strategy via α-cyano ethers was extensively applied in the assembly of the F and IJ ring fragments to afford the FGHIJ ring unit, followed by coupling with the ABC ring unit.

Key words

polyether - convergent synthesis - α-cyano ether - ring-closing metathesis - reductive etherification

13

The carbon numbering of compounds in this paper corresponds to that of YTX.

22

Physical Data of 2
[α]D ³0 -10.8 (c 0.04, CHCl3). ¹H NMR (500 MHz, C6D6): δ = 7.30-6.99 (10 H, m, Ph), 4.41 (1 H, d, J = 12.0 Hz, Bn), 4.37 (1 H, d, J = 12.0 Hz, Bn), 4.33 (1 H, d, J = 12.0 Hz, Bn), 4.18 (1 H, d, J = 12.0 Hz, Bn), 4.00 (1 H, d, J = 2.5 Hz, H32), 3.88 (1 H, ddd, J = 11.5, 10.0, 4.5 Hz, H30), 3.82 (1 H, dd, J = 13.5, 4.0 Hz, H34), 3.72 (1 H, m, H37), 3.65 (1 H, dd, J = 11.0, 4.0 Hz, H38), 3.60 (1 H, dd, J = 11.0, 2.0 Hz, H38), 3.49 (4 H, m, H1, H1, H4, H36), 3.31 (1 H, ddd, J = 10.5, 9.5, 4.0 Hz, H15), 3.27-3.19 (3 H, m, H7, H20, H22), 3.15 (1 H, ddd, J = 9.5, 9.0, 5.5 Hz, H16), 3.12-3.07 (2 H, m, H13, H28), 3.05-3.00 (3 H, m, H9, H10, H31), 2.94-2.88 (2 H, m, H6, H12), 2.64 (1 H, dd, J = 9.5, 9.0 Hz, H27), 2.59 (1 H, ddd, J = 12.0, 4.5, 4.0 Hz, H14), 2.52 (1 H, ddd, J = 10.5, 4.5, 4.0 Hz, H11), 2.42 (1 H, ddd, J = 10.5, 4.5, 4.0 Hz, H29), 2.36-2.29 (2 H, m, H8, H35), 2.20 (1 H, ddd, J = 10.5, 4.0, 4.0 Hz, H5), 2.05-1.98 (2 H, m, H17, H17), 1.91-1.81 (5 H, m, H18, H18, H21, H24, H25), 1.76-1.62 (9 H, m, H2, H2, H5, H11, H14, H21, H26, H29, H35), 1.60-1.53 (2 H, m, H8, H24), 1.41 (1 H, dddd, J = 10.0, 9.0, 9.0, 2.5 Hz, H25), 1.27 (3 H, s, Me), 1.26 (3 H, s, Me), 1.16 (3 H, d, J = 6.0 Hz, 26-Me), 1.11 (3 H, s, Me), 1.00 (3 H, s, Me). ¹³C NMR (150 MHz, C6D6): δ = 139.95, 138.84, 88.61, 86.22, 82.89, 81.83, 81.22, 80.45, 78.97, 78.67, 78.04, 77.82, 77.56 (2 ×), 77.24, 76.86, 75.81, 74.93, 73.43 (3 ×), 73.15, 72.26, 71.62, 71.45, 70.96, 69.80, 69.74, 58.75, 46.50, 43.76, 40.46, 39.87, 39.49, 37.70, 36.21, 35.95, 34.53, 32.74, 32.07, 30.15, 29.78, 23.56, 22.11, 20.59, 14.84, 14.30 (signals of aromatic region are overlapped with solvent). IR (film): ν = 3437, 2928, 2874, 1453, 1378, 1340, 1286, 1204, 1068, 1025, 738, 698 cm-¹. HRMS (ESI-TOF): m/z calcd for C57H80O15Na: 1027.5395 [M + Na]+; found: 1027.5398.