Total syntheses of Tetrodotoxin and 9-epiTetrodotoxin
Peihao Chen, Jing Wang, Shuangfeng Zhang, Yan Wang, Yuze Sun, Songlin Bai, Qingcui Wu, Xinyu Cheng, Peng Cao, Xiangbing Qi
Abstract
Abstract Tetrodotoxin and congeners are specific voltage-gated sodium channel blockers that exhibit remarkable anesthetic and analgesic effects. Here, we present a scalable asymmetric syntheses of Tetrodotoxin and 9- epi Tetrodotoxin from the abundant chemical feedstock furfuryl alcohol. The optically pure cyclohexane skeleton is assembled via a stereoselective Diels-Alder reaction. The dense heteroatom substituents are established sequentially by a series of functional group interconversions on highly oxygenated cyclohexane frameworks, including a chemoselective cyclic anhydride opening, and a decarboxylative hydroxylation. An innovative SmI 2 -mediated concurrent fragmentation, an oxo-bridge ring opening and ester reduction followed by an Upjohn dihydroxylation deliver the highly oxidized skeleton. Ruthenium-catalyzed oxidative alkyne cleavage and formation of the hemiaminal and orthoester under acidic conditions enable the rapid assembly of Tetrodotoxin, anhydro-Tetrodotoxin, 9- epi Tetrodotoxin, and 9- epi lactone-Tetrodotoxin.