1. Department of Organic Chemistry, Faculty of Science, University of Yaoundé I, P. O. Box +(237) 812, Yaoundé, Cameroon. Fax: +237-22-235396
2. Department of Chemistry, Higher Teacher Training School, University of Yaoundé I, P. O. Box +(237) 47, Yaoundé, Cameroon. Fax: +237-22-235396
3. Department of Chemistry, Faculty of Science, University of Botswana, P. Bag 00704, Gaborone, Botswana