New 23-Spirocholestane Derivatives from Ypsilandra thibetica. - Bai-Bo Xie; Chang-Xiang Chen; Yong-Hui Guo; Yu-Ye Li; Ya-Juan Liu; Wei Ni; Liu-Meng Yang; Ning-Bo Gong; Yong-Tang Zheng; Rui-Rui Wang; Yang Lü; Hai-Yang Liu (Planta Medica, 2013)