1. Department of Chemistry, Faculty of Science, Sultan Qaboos University, P.O. Box 36, 123 Muscat, Oman
2. PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
3. Institute of Pharmaceutical Biology, Section Molecular-, Cellular-, and Pharmacobiology, University of Bonn, Nußallee 6, 53115 Bonn, Germany
4. CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Pudong, Shanghai 201203, China