1. Department
of Chemistry, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
2. Department
of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Ernst-Moritz-Arndt University Greifswald, 17487 Greifswald, Germany
3. Institute
of Chemistry, University of Neuchatel, 51 Ave de Bellevaux, CH-2000 Neuchatel, Switzerland