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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The rearrangement was attempted with
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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.
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