1. Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutics and Experimental Therapeutics, College of PharmacyUniversity of Iowa Iowa City, Iowa 52246 USA
2. Department of Biochemistry, Carver College of MedicineUniversity of Iowa Iowa City, Iowa 52246 USA
3. NMR Core Facility, Carver College of MedicineUniversity of Iowa Iowa City, Iowa 52246 USA