Synthesis and biological evaluation of antitumour-active betulin derivatives.

The reaction of betulinic aldehydes with various carbon nucleophiles gave a series of new betulin derivatives, among them epoxides, glycidic derivatives and beta-hydroxy carbonyl compounds. Subsequent transformations of the beta-hydroxy carbonyls lead to 1,3-diketo- and alpha,beta-unsaturated betulin derivatives. These compounds were assayed for cytotoxicity using 15 human cancer cell lines and a colorimetric SRB-assay. Several compounds revealed significant antitumour activity.