1. Laboratory
of Bioorganic Chemistry, National Institute of Diabetes and Digestive
and Kidney Diseases, National Institutes of Health, Building 8A,
Room B1A-19, Bethesda, Maryland 20892-0810, United States
2. Department
of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104, United States
3. Department
of Pharmacology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States