1. a Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education , Hunan Province College Key Laboratory of QSAR/QSPR, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology , Xiangtan 411201, China
2. b Department of Chemistry and The Skaggs Institute for Chemical Biology , The Scripps Research Institute , 10550 N. Torrey Pines Road, La Jolla, California 92037, USA