1. State Key Laboratory of Phytochemistry and Plant Resources in West China, and Key Laboratory of Biodiversity and Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, P. R. China, Department of Chemistry, Fudan University, Shanghai 200433, P. R. China, Department of Chemistry, Yunnan University, Kunming 650091, P. R. China, and Graduate School of Chinese Academy of Sciences, Beijing 100039, P. R. China