Chemical Modification of Triterpenes From Lantana camara. 22β-Ester Analogues of Lantadene A

Abstract

The partial syntheses of the hepatotoxic triterpenes lantadene A (1) and lantadene B (2) are described. A number of new C22 ester analogues of lantadene A were also synthesized. The preferred route to these esters involved esterification of diphenylmethyl 22β-hydroxyoleanonate (8) and selective cleavage of the diphenylmethyl ester function. In some cases, the hydroxy acid (3) was esterified directly. In the N.M.R. spectra of the diphenylmethyl esters, some signals appeared at unusually high field due to anisotropic shielding.