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Synlett 2009(1): 32-34  
DOI: 10.1055/s-0028-1087382
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Enantioselective First Total Syntheses of 2-(Formylamino)trachyopsane and ent-2-(Isocyano)trachyopsane via a Biomimetic Approach

A. Srikrishna*, G. Ravi, D. R. C.
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India
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Publication History

Received 10 July 2008
Publication Date:
12 December 2008 (online)

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Abstract

A biomimetic rearrangement of an isotwistane to a tri­cyclo[4.3.1.0³,8]decane has been employed as the key step for the enantioselective first total syntheses of the marine sesquiterpenes 2-(formylamino)trachyopsane and ent-2-(isocyano)trachyopsanes ascertaining the biogenetic relationship between the marine sesqui­terpenes neopupukeananes and trachyopsanes.

Key words

natural products - marine sesquiterpenes - enantioselective synthesis - biomimetic synthesis - acid-catalysed rearrangement

    References and Notes

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6

So far there is no report in the literature on the total synthesis or model studies of any racemic or optically active trachyopsanes.

8

The rearrangement was attempted with BF3˙OEt2, BF3˙OEt2 in the presence of TFA, TFA, MeSO2OH, and concentrated H2SO4; in all these experiments either starting material recovered or a complex mixture was produced. Reaction with formic acid generated the formate ester of the alcohol 17, whereas PTSA (1 equiv) in MeCN produced a mixture of the acetate and tosylates of the alcohol 17 along with the rearranged product 18. Significant amount (50-60%) of rearranged product 18 was formed when the reaction was carried out with PTSA (1 equiv) in refluxing benzene.