1. Department of Organic Chemistry, Faculty of Sciences, University of Yaoundé 1, Yaoundé, Cameroon
2. Department of Chemistry, Higher Teachers Training College, University of Yaoundé 1, Yaoundé, Cameroon
3. Université de Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, UMR CNRS ISCR 6226, Rennes, France