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Synlett 2005(18): 2767-2768  
DOI: 10.1055/s-2005-918954
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Palladium-Assisted Ring Annulation for the Synthesis of the Batrachotoxin Ring System

Pierre Lacrouts, Philip J. Parsons*, Clive S. Penkett, Abdul Rauf Raza
Department of Chemistry, School of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex BN1 9QJ, UK
Fax: +44(1273)678661; e-Mail: P.J.Parsons@sussex.ac.uk;
Further Information

Publication History

Received 1 July 2005
Publication Date:
21 October 2005 (online)

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Abstract

A method for the synthesis of the steroidal nucleus in general and in particular for the cardiotoxin batrachotoxin has been carried out using a ‘one-pot’ palladium-mediated annulation sequence.

Key words

palladium - cyclisation - microwave

    References

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    Typical Experimental Procedure for the Synthesis of Tetracycle 3.
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    Physical Data for 3. R f = 0.56 (Et2O-PE 1:1). IR: νmax = 2974 (C=C-H), 2933 (sat. C-H), 1714 (α,β-unsat.C=O) cm-1. [α]D 24 -81.4 (c 1.02, CHCl3). ESI-MS [M + Na]+ (amu): 323.1616 (found), 323.1618 (calcd; 0.2 mmu difference). LRMS (EI): m/z (%) = 300(100) [M+ ], 285 (9) [M+ - Me], 272 (12) [M+ - CO]. H1 NMR (300 MHz, CDCl3): δ = 0.69 (s, 3 H, C-CH3), 1.40 (m, 1 H, 7-Hα), 1.52 (ddd, 1 H J = 13.6, 12.5, 5.0 Hz, 16-Hα), 1.65-2.00 (m, 6 H, 12-H, 13-H, 11-Hα, 13-H, 15-H), 2.14 (d, 3 H, J = 2.9 Hz, =C-CH3), 2.17-2.31 (m, 3 H, 11-Hβ, 7-Hβ, 16-Hβ), 2.40-2.55 (m, 2 H, 6-H), 3.23 (s, OCH3), 3.85 (m, 1 H, 8-H), 5.39 (m, 1 H, 10-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 13.0 (q), 19.4 (q), 27.3 (t), 30.1 (s), 30.7, 30.9, 31.2 (t), 37.0 (d), 37.1 (t), 44.0 (t), 48.5 (d), 50.0 (q), 93.5 (s), 98.1 (s), 117.0 (d), 143.9, 145.1, 145.9 (s), 204.4 (s) ppm.

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