1. Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics; Chengdu University; Chengdu People's Republic of China 610052
2. Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Sichuan Industrial Institute of Antibiotics; Chengdu University; Chengdu People's Republic of China 610052
3. Institut fuer Organische und Biomolekulare Chemie, Georg-August-Universitaet; Tammannstrasse 2 37077 Goettingen Germany