Ramos, SS;
Almeida, P;
Santos, L;
Motherwell, WB;
Sheppard, TD;
Costa, MD;
(2007)
Functionalisation of terpenoids at C-4 via organopalladium dimers: cyclopropane formation during oxidation of homoallylic sigma-organopalladium intermediates with lead tetraacetate.
TETRAHEDRON
, 63
(51)
12608 - 12615.
10.1016/j.tet.2007.10.016.
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Abstract
The synthesis of new potential adjuvant saponin aglycons was investigated by selective palladium mediated C-H functionalisation of appropriately functionalised derivatives of lanosterol, cholesterol, and friedelin. The desired equatorial aldehyde functionality was successfully introduced into the lanosterol skeleton as expected. Cyclopalladation of a cholesterol derivative proceeded as expected, but during oxidation of the organopalladium intermediate, participation of the adjacent alkene functionality led to stereoselective formation of a cyclopropane and introduction of an acetate group into the steroid backbone at C-6. Further investigation of this unusual cyclopropane formation on a model decalin system confirmed the result, but C-H activation on a related open chain system was prevented by complexation of the alkene functionality to the palladium. (c) 2007 Elsevier Ltd. All rights reserved.
| Type: | Article |
|---|---|
| Title: | Functionalisation of terpenoids at C-4 via organopalladium dimers: cyclopropane formation during oxidation of homoallylic sigma-organopalladium intermediates with lead tetraacetate |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.tet.2007.10.016 |
| Publisher version: | http://dx.doi.org/10.1016/j.tet.2007.10.016 |
| Language: | English |
| Keywords: | SAPONINS |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/170115 |
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