Synthesis of a Tricyclic Bisguanidine Compound Structurally Related to Saxitoxin and its Identification in Paralytic Shellfish Toxin‐Producing Microorganisms |
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Authors: | Shigeki Tsuchiya Dr. Yuko Cho Prof. Dr. Keiichi Konoki Prof. Dr. Kazuo Nagasawa Prof. Dr. Yasukatsu Oshima Prof. Dr. Mari Yotsu‐Yamashita |
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Affiliation: | 1. Graduate School of Agricultural Science, Tohoku University, Tsutsumidori‐Amamiya, Aoba‐ku, Sendai 981‐8555 (Japan);2. Faculty of Technology, Tokyo University of Agriculture and Technology, 2‐24‐16 Naka‐cho, Koganei‐shi, Tokyo 184‐8588 (Japan);3. Graduate School of Life Sciences, Tohoku University, 2‐1‐1 Katahira, Aoba‐ku, Sendai 980‐8577 (Japan) |
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Abstract: | We recently reported the chemical synthesis and identification of the genetically predicted biosynthetic intermediates of saxitoxin (STX), including a 2‐aminoimidazole‐bearing monoguanidine compound (Int‐C′2) in two paralytic shellfish toxin (PST)‐producing microorganisms. In this study, we achieved the direct conversion of Int‐C′2 into a tricyclic bisguanidine compound (called Cyclic‐C′), which is structurally related to STX, through oxidative intramolecular guanidine transfer to 2‐aminoimidazole catalyzed by Pd/C under basic conditions in air. By using HPLC‐MS analysis, Cyclic‐C′ was also identified in the PST‐producing microorganisms, suggesting that Cyclic‐C′ is either another biosynthetic intermediate or a shunt product of PSTs. In addition, a weak inhibitory activity of Cyclic‐C′ to the voltage‐gated sodium channels was detected by using a cell‐based assay. |
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Keywords: | biosynthesis cyclization natural products palladium toxicology |
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