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