1. Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium, Division of Pharmacology, University of Cape Town, K45, OMB, Groote Schuur Hospital, Observatory, 7925, South Africa, Department of Chemistry and Institute of Infectious Disease & Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa