The application of functionalized polymers to site-directed delivery of the antiulcer prostaglandin, misoprostol, is described. By use of homogeneous catalysis, the simple polymer, polybutadiene, was modified to incorporate the specialized requirements for controlled delivery of misoprostol to the stomach. An acid labile silyl ether bond to the C-11 hydroxyl of misoprostol was installed as the primary rate determining step for drug release, and a series of analogs, in which the steric hindrance about the silicon atom was varied, was prepared and evaluated for in vitro release rates, efficacy against indomethacin induced gastric damage and diarrheagenic activity. The diisopropylsilyl analog, the slowest releasing system studied, showed efficacy equal to misoprostol against indomethacin-induced gastric damage and no diarrhea at the highest dose tested.