1. Chemistry DepartmentFaculty of ScienceMinia University El-Minia 61519 Egypt
2. Institute of Organic ChemistryKarlsruhe Institute of Technology, Fritz- Haber-Weg 6 76131 Karlsruhe Germany
3. Department of ChemistryUniversity of Helsinki, P.O. Box 55 (A. I. Virtasen aukio I) 00014 University of Helsinki Finland