1. Shaanxi Key Laboratory of Natural Products & Chemical Biology
2. College of Science
3. Northwest A&F University
4. Yangling 712100
5. P. R. China
6. Dipartimento di Chimica e Chimica Industriale
7. Università di Pisa
8. I-56124 Pisa
9. Italy
10. Division of Organic Chemistry and Biochemistry
11. College of Pharmacy
12. Chungnam National University
13. Daejeon 305-764
14. Republic of Korea