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Synthesis of the Paralytic Shellfish Poisons (+)-Gonyautoxin 2, (+)-Gonyautoxin 3, and (+)-11,11-Dihydroxysaxitoxin
John V Mulcahy1, James R Walker1, Jeffrey E Merit1
1Department of Chemistry, Stanford University , Stanford, California 94305-0080, United States.
Abstract:
The paralytic shellfish poisons are a collection of guanidine-containing natural products that are biosynthesized by prokaryote and eukaryote marine organisms. These compounds bind and inhibit isoforms of the mammalian voltage-gated Na(+) ion channel at concentrations ranging from 10(-11) to 10(-5) M. Here, we describe the de novo synthesis of three paralytic shellfish poisons, gonyautoxin 2, gonyautoxin 3, and 11,11-dihydroxysaxitoxin. Key steps include a diastereoselective Pictet-Spengler reaction and an intramolecular amination of an N-guanidyl pyrrole by a sulfonyl guanidine. The IC50's of GTX 2, GTX 3, and 11,11-dhSTX have been measured against rat NaV1.4, and are found to be 22 nM, 15 nM, and 2.2 μM, respectively.
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