Novel compounds useful as chemotherapeutic and chemopreventive agents are provided. The compounds are analogs of polyphenol catechins that occur in green tea, such as epigallocatichin-3-gallate (EGCG), and have the structure of formula (I) ##STR00001## wherein R.sup.1 through R.sup.11 are defined herein. Preferred R.sup.4 moieties are selected from O, S, NH and CH.sub.2, and in exemplary compounds, R.sup.4 is O and R.sup.5 is a tri-substituted aroyloxy substituent, such as a 3,4,5-substituted benzoyloxy group. Pharmaceutical compositions are provided as well, as are methods of chemotherapy and chemoprevention.