1. Faculty of Science, Department of Organic Chemistry , University of Yaounde I , PO Box 812 , Yaounde , Cameroon
2. Département de Chimie , Université de N’Djamena , N’Djamena , Chad
3. Faculty of Science, Department of Organic Chemistry , University of Yaounde I , PO Box 812 , Yaounde , Cameroon , E-mail: