Article ID Journal Published Year Pages File Type
5226962 Tetrahedron 2007 8 Pages PDF
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.

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Related Topics
Physical Sciences and Engineering Chemistry Organic Chemistry
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