1. State Key Laboratory of Medicinal Chemical biology; Nankai University; Tianjin 300071 China
2. College of Chemistry; Nankai University; Tianjin 300071 China
3. Department of Chemical Sciences; Bernal Institute; University of Limerick; Limerick V94XT66 Republic of Ireland
4. Department of Chemistry; University of South Florida; Tampa FL 33620 USA
5. College of Pharmacy; Nankai University; Tianjin 300071 China