Suffrutines A and B: a pair of Z/E isomeric indolizidine alkaloids from the roots of Flueggea suffruticosa - Wu, Z L; Zhao, B X; Huang, X J; Tang, G Y; Shi, L; Jiang, R W; Liu, X; Wang, Y; Ye, W C (Angew Chem Int Ed Engl, 2014)