1. Department of Chemistry, Indiana State University, 600 Chestnut Street, Science S35E, Terre Haute, Indiana 47809, Department of Chemistry, Wabash College, P.O. Box 352, Crawfordsville, Indiana 47933, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, and Chiralix B.V., P.O. Box 31070, 6503 CB Nijmegen, The Netherlands