1. Department of Medicinal Chemistry and Natural Products, School of Pharmacy, P. O. Box 12065, Medical Faculty, The Hebrew University of Jerusalem, Ein Kerem, 91120 Jerusalem, Israel
2. Institute of Microbiology, Czech Academy of Sciences, Vídenská 1083, 142 20 Prague, Czech Republic
3. Chemistry and Chemical Technology Department, P.O. Box 20002, Al-Quds University, Abu-Deis, Palestine