Diastereoselective Synthesis of Chiral [4.4]- and [4.5]-Spiroketals from Furan Derivatives: Study on the Asymmetric Synthesis of Tonghaosu Analogs - Yin, Biao-Lin; Hu, Tai-Shan; Yue, Hui-Juan; Gao, Yang; Wu, Wen-Min; Wu, Yu-Lin (Synlett, 2004)