1. Organic & Medicinal Chemistry, Department of Chemistry, Center for Chemico- and Biomedicinal Research (CCBR), Faculty of Science, Rhodes University, Grahamstown 6140, Eastern Cape, South Africa
2. Department of Chemistry, The University of Manchester, Manchester M13 9PL, UK
3. Center for Chemico- and Biomedicinal Research (CCBR), Faculty of Science, Rhodes University, Grahamstown 6140, Eastern Cape, South Africa