1. Departments of Chemistry and Medicinal Chemistry, State University of New York at Buffalo, Buffalo, New York 14260, Department of Biochemistry and Biophysics, University of Rochester Medical Center, 601 Elmwood Avenue, Box 607, Rochester, New York 14642, Department of Dermatology and PDT Center, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263, and Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115