Chao Wang1, Xinjun Wu1,2, Li Zhou1, Jian Sun1. 1. Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041 (China), Fax: (+86) 28-85222753. 2. Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041 (China).