1. Organic and Bioorganic Chemistry, Faculty of Chemistry; Bielefeld University; D-33501 Bielefeld Germany
2. Chemistry Department, Faculty of Science; Al-Azhar University; Nasr City-Cairo 11884 Egypt
3. Microbial Chemistry Department, Division of Genetic Engineering and Biotechnology Research; National Research Centre; El-Buhouth St. 33, Dokki-Giza 12622 Egypt
4. Chemistry of Natural Compounds Department, Pharmaceutical and Drug Industries Research Division; National Research Centre; El-Buhouth St. 33, Dokki-Giza 12622 Egypt