1. Departments of Chemistry and of Chemical Engineering and Material Science, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803-1804, and Pharmaceutical Research & Development, Merck & Company Inc., P.O. Box 4, WP78-304, West Point, Pennsylvania 19486