Abstract Seventeen steviol derivatives, ie, 2–18, and 19 isosteviol derivatives, ie, 19–37, were prepared from a diterpenoid glycoside, stevioside (1). Upon evaluation of the cytotoxic activities of these compounds against leukemia (HL60), lung (A549), stomach (AZ521), and breast (SK-BR-3) cancer cell lines, nine steviol derivatives, ie, 5–9 and 11–14, and five isosteviol derivatives, ie, 28–32, exhibited activities with single-digit micromolar IC 50 ...