This is a Research Planning Grant (RPG) of the Research Opportunities for Women Initiative (ROW) that is being made by the Organic and Macromolecular Chemistry Program of the Chemistry Division. It will provide Dr. Linda A. Jacob of the University of Scranton with resources and time to develop a research program. The electrophilic substitution of aryltrimethylsilanes will be studied as a method for preparing phosphorous or fluorine containing aromatic amino acids. The initial focus will be on simpler structures such as F-18 labelled peptides that might find use in radio imaging or where appropriate with magnetic imaging techniques. The latter aspects will be carried out cooperatively with scientists at New York University Medical School.