Synlett 2008(7): 971-974  
DOI: 10.1055/s-2008-1042918
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Dictyopterene A

Erwin Hohn, Jiří Paleček, Jörg Pietruszka*
Institut für Bioorganische Chemie, Heinrich-Heine-Universität Düsseldorf im Forschungszentrum Jülich, Im Stetternicher Forst, Geb. 15.8, 52426 Jülich, Germany
Fax: +49(2461)616196; e-Mail: j.pietruszka@fz-juelich.de;
Further Information

Publication History

Received 5 January 2008
Publication Date:
17 March 2008 (online)

Abstract

The total synthesis of dictyopterene A was accomplished via an enantiomerically pure cyclopropylboronic ester building block. Crucial olefination steps were carried out employing the Julia-Kocienski as well as the Wittig reactions. The Matteson homologation was the final key step for the total synthesis.

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Later, (1S,2S)-dictyopterene B enantiomer was discovered us a minor component in female gametes and essential oils of families Scytosiphonaceae, Chordariaceae, Dictyo-taceae, see ref. 2m.

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Thematic issue on cyclopropane chemistry (guest editor: A. de Meijere): Chem. Rev. 2002, 103, 931-1647.

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Representative Procedure - Synthesis of E -olefin 6 To a stirred solution of the sulfone 7 (0.08 g, 0.28 mmol, 1.5 equiv) in anhyd DME (4 mL) at -60 °C under N2 was added dropwise via cannula a solution of KHMDS (0.07 g, 0.34 mmol, 1.8 equiv) in anhyd DME (2 mL) over 5 min. The yellow-orange solution was stirred for 5 min and the aldehyde 3 (0.1 g, 0.19 mmol, 1 equiv) in anhyd DME (2 mL) was added dropwise via cannula over 5 min. The reaction mixture was stirred additional 10 min at -60 °C and was then quenched with H2O (1 mL). The mixture was stirred vigorously whilst warming to r.t., diluted with Et2O (4 mL) and H2O (4 mL), and finally extracted with Et2O (3 × 4 mL). The combined organic layers were dried (MgSO4), filtered, and concentrated under reduced pressure. The crude product 6 was purified by flash column chromatography (SiO2, petroleum ether-EtOAc, 95:5) to afford the E-olefin 6 (0.10 g, 93%) as colorless crystals; E/Z > 99:1. The minor Z-isomer 6 was only detected by 600 MHz 1H NMR and was removed by a single recrystallization from pentane.
E-Olefin 6: [α]D 20 -79.7 (c 1.0, CHCl3); mp 113 °C. Anal. Calcd for C39H43BO4 (586.57): C, 79.86; H, 7.39. Found: C, 79.91; H, 7.31. MS-FAB (NBA + NaI): m/z (%) = 609 (<5) [M + Na+], 197 (100) [Ph2COCH3 +], 167 (12) [Ph2C+], 105 (10) [C7H5O+], 77 (6) [C6H5 +]. IR (film): 3060, 3024, 2956, 2932, 2833, 1493, 1446, 1421, 1366, 1239, 1184, 1075, 1032, 1019, 965, 921, 857 cm-1. 1H NMR (600 MHz, CDCl3): δ = -0.53 (ddd, 3 J 1 ′,3 ′b = 9.8 Hz, 3 J 1 ′,3 ′a = 6.5 Hz, 3 J 1 ′,2 = 5.3 Hz, 1 H, 1′-H), 0.24 (ddd, 3 J 2 ′,3a = 7.8 Hz, 3 J 1 ′,3 ′a = 6.4 Hz, 3 J 3 ′a,3 ′b = 3.4 Hz, 1 H, 3′-Ha), 0.34 (ddd, 3 J 1 ′,3 ′b = 9.8 Hz, 3 J 2 ′,3 ′b = 6.5 Hz, 3 J 3 ′a, 3 ′b = 3.4 Hz, 1 H, 3′-Hb), 0.91 (t, 3 J 5 ′′,6 ′′ = 7.2 Hz, 3 H, 6′′-H), 1.17-1.27 (m, 1 H, 2′-H), 1.28-1.36 (m, 4 H, 4′′-H, 5′′-H), 1.95 (m, 2 H, 3′′-H), 2.99 (s, 6 H, OCH3), 4.79 (dd, 3 J 1 ′′,2 ′′ = 15.1 Hz, 3 J 1 ′′,2 = 8.5 Hz, 1 H, 1′′-H), 5.25 (s, 2 H, 4-H, 5-H), 5.51 (dt, 3 J 1 ′′,2 ′′ = 15.1 Hz, 3 J 2 ′′,3 ′′ = 6.9 Hz, 1 H, 2′′-H), 7.27-7.34 (m, 20 H, arom. H). 13C NMR (125 MHz, CDCl3): δ = 1.8 (C-1′), 12.4 (C-6′′), 13.8 (C-3′), 21.0 (C-5′′), 22.1 (C-4′′), 27.2 (C-2′), 31.8 (C-3′′), 51.7 (CPh2OCH3), 77.7 (C-4 and C-5), 83.3 (CPh2OCH3), 127.1, 127.2, 127.4, 127.7, 128.1, 128.3 (arom. CH), 129.6 (C-1′′), 133.5 (C-2′′), 141.1, 141.3 (arom. Cipso).

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(-)-(1S,2S)-Dictyopterene A (1): [α]D 20 -69.3 (c 0.40, CHCl3); ref. 2d: [α]D 22 +72 (c 6.74, CHCl3) for the 1R,2R-enantiomer. GC-MS (EI, 70 eV): m/z (%) = 150 (100) [M+], 135 (15) [M+ - CH3], 122 (24) [M - C2H4 +], 121 (60) [M - C2H5 +]. 1H NMR (600 MHz, CDCl3): δ = 0.75-0.84 (m, 2 H, 3′-H), 0.87 (t, 3 J 5 ′′,6 ′′ = 7.0 Hz, 3 H, 6′′-H), 1.25-1.35 (m, 4 H, 4′′ and 5′′-H), 1.36-1.41 (m, 2 H, 1′-H and 2′-H), 1.95-2.05 (m, 2 H, 3′′-H), 4.84 (dd, 3 J 1,2 = 10.2 Hz, 2 J 2a,2b = 2.3 Hz, 1 H, 2-Ha), 4.98 (dd, 3 J 1,2 = 17.2 Hz, 2 J 2a,2b = 2.3 Hz, 1 H, 2-Hb), 5.03 (dd, 3 J 1 ′′,2 ′′ = 15.1 Hz, 3 J 1 ′′,2 = 6.1 Hz, 1 H, 1′′-H), 5.36 (ddd, 3 J 1,2 = 10.2 Hz, 3 J 1,2 = 17.2 Hz, 3 J 1,1 = 6.7 Hz, 1 H, 1-H), 5.46 (dt, 3 J 1 ′′,2 ′′ = 15.1 Hz, 3 J 2 ′′,3 ′′ = 6.9 Hz, 1 H, 2′′-H). 13C NMR (150 MHz, CDCl3): δ = 14.1 (C-6′′), 14.8 (C-3′), 22.3 (C-5′′), 23.6 (C-2′), 24.3 (C-1′), 31.8 (C-4′′), 32.2 (C-3′′), 111.8 (C-2), 129.2 (C-2′′), 131.6 (C-1′′), 140.9 (C-1).