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A general synthetic route to monoterpenes and sesquiterpenes

University of British Columbia

A biogenetic hypothesis concerned with an alternative route to monoterpenes and sesquiterpenes bearing the bicyclo(2.2.1)heptane framework has led to a general synthetic route to this class of compound. In particular, consideration of an oxygenated monocyclic cyclohexenyl substrate resembling dihydrocarvone enol phosphate as possible intermediate in the biogenesis of camphor has resulted in development of an efficient laboratory synthesis of (±)-camphor 17 and related compounds including borneol 18, tricyclene 19 and camphene 20. Extention of this work in the monoterpene field to the related sesquiterpenes provided synthetic entry to (±)-campherenone 42, (±)-epicampherenone 47, (±)-∝-santalene 47, (±)-β-santalene 48 and (±)-epi-β-santalene 50. As a further simplification of the biogenesis of sesquiterpenes, campherenone enol phosphate was considered a possibl precursor of such polycyclic sesquiterpenes as copacamphor, ylango-camphor, longicamphor and structurally related compounds. Laboratory analogy for this biogenetic relationship was established in the synthesis of (±)-copacamphor 52, (±)-ylangocamphor 53 and related compounds starting from campherenone. The success of the synthetic investigations led to refinements in the initial biogenetic postulate and necessitated the establishment of the absolute configurations of various sesquiterpenes encompassed in the postulate. (-)-Cryptomerion 99a was prepared starting from (-)-carvone 79a. A synthesis of (+)-epicampherenone 45a and (-)-campherenone 42b starting from (+)-camphor has allowed assignment of absolute configuration to these compounds and to β-santalene and epi-β-santalene. Formal access to optically active copacamphor, ylangocamphor and related compounds is implied from the synthesis of (-)-campherenone.

Text

2011-03-21

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http://hdl.handle.net/2429/32647

Chemistry

University of British Columbia

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