ORGN 911 |
| (+)-Aquaticol (1) is a novel bis-sesquiterpene with an unusual structure isolated in 1999 from the chinese plant Veronica anagallis aquatica that is used in traditional medecine. The biomimetic synthesis of (3R,10S,14R,23S)-aquaticol (1) involves the dimerization of two identicals (6R,8S)-o-quinols 3 by a Diels-Alder reaction. We developed a total synthesis of aquaticol (1) based on the racemic oxidation of (S)-hydroxycuparene (2) using hypervalent iodine SIBX to produce a 1:1 mixture of (6R,8S)-o-quinol 3 and (6S,8S)-o-quinol 4 which dimerize spontaneously with an extraordinary diastereoselectivity to give only two homo-dimerization products : (+)-(3R,10S,14R,23S)-aquaticol (1) and the unnatural (-)-(3S,10S,14S,23S)-dimer 5 diastereoisomer. Such a dimerization of o-quinols is a well known process in organic chemistry but its regio- and diastereofacial differentiation still awaits a clear rationalisation. We discussed these results in the light of the Cieplak model and computer aided modelisation from transition state structures that we designed.
|
|
Total Synthesis of Complex Molecules
1:00 PM-5:00 PM, Thursday, 14 September 2006 Moscone Center -- Room 134, Oral
Division of Organic Chemistry |
