1. Department of Organic ChemistryUniversity of Valencia Dr. Moliner 50 46100 Burjassot Valencia Spain
2. Physical and Theoretical Chemistry LaboratoryFaculty of Science, University of Yaoundé I P.O. Box 812 Yaoundé Cameroon
3. Department of ChemistryHigh Teacher Training CollegeUniversity of Yaoundé I P. O. Box 47 Yaoundé Cameroon