Developments of Highly Stereoselective Constructions of Steroid Side Chains and Their Application to the Synthesis of Natural Products. Toshio HONDA* and Masayoshi TSUBUKI* Steroids are one of the most interesting and the most widely distributed and also one of the most structurally complex families of naturally occurring substances. Due to their great importance for biology and medicine , in tensive efforts have been devoted into their synthesis. Especially , stereoselective construction of

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... roidal side chains has been the subject of extensive synthetic efforts, because their physiological activity has been reflected in the stereochemistry of the side chain . This article describes the highly stereoselective construction of steroidal side chains , where furan and its analogues are employed as the carbon-unit sources of the side chains . Moreover the strategies developed above are applied to the synthesis of several natural products , such as bras sinolide and ecdysone.