Abstract: With stigmasterol as the starting material, 24-methylenecholest-5-en-3%β%,19-diol(1), a cytotoxic hydroxylated sterol, was synthesized in 10 steps in 16% overall yield. The side chain of stigmasterol was converted to a keto-containing structure 4 %via% ozonization, the Wittig reaction and hydrogenation. The key intermediate cholest-5-en-24-oxo-3%β%,19-diol(8) from compound 4 was prepared according to the following procedures: HOBr addition, lead tetraacetate/I₂-irradiation reaction, zinc dust reduction and KOH/CH₃OH hydrolyzation. Finally, the synthesis of the target product 1 was completed by the Wittig reaction with methenetriphenylphosphorane. The physical constants and NMR data of compound 1 were identical with those of the natural product. This is the first report for the synthesis of 24-methylenecholest-5-en-3%β%,19-diol(1). Compound 1 exhibits a significant cytotoxic activity against human CN2 and Mgc803 cell lines with IC₅₀ values of 3.5 and 4.0 μg/mL respectively.

Key words: Hydroxylated sterol, 24-Methylenecholest-5-en-3β,19-diol, Synthesis