1. Departments of Chemistry and Chemical Biology, Chemical and Biological Engineering, and Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, Centro de Investigaciones Biológicas (CSIC), Ramiro Maeztu 9, 28040 Madrid, Spain, Universidad de La Rioja UA-CSIC, Madre de Dios 5, 26006 Logroño, Spain, and Division of Medicinal Chemistry and Natural Products, University of North Carolina, Chapel Hill, North Carolina 27599