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Concise Synthesis of the Core Structures of Saundersiosides

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posted on 15.05.2015, 00:00 by Shou-Ling Cheng, Xiao-Ling Jiang, Yong Shi, Wei-Sheng Tian
A divergent synthesis of three core pentacyclic lactones of nine rearranged cholestane sapogenins, saundersiosides A–H (18) and candicanoside A (9), is reported. Key features include a one-flask CBS reduction/Brown hydroboration–oxidation, a SmI2-mediated intramolecular Reformatskii reaction, and an intramolecular transesterification. This synthesis provides a general strategy and key precursors for the collective synthesis of natural and designed saundersiosides. An efficient formal synthesis of candicanoside A is also achieved.