AI Article Synopsis
- A new stereoselective method is developed to synthesize the bis-guanidinium toxin (+)-saxitoxin, which is known for causing paralytic shellfish poisoning during red tides.
- The synthesis process involves an unusual nine-membered ring guanidine intermediate and only requires four additional steps to achieve the final product, utilizing a specific catalytic oxidation reaction.
- Two main routes to create the critical guanidine intermediate are explored: one uses Rh-catalyzed C-H amination, while the other employs a stereoselective addition method, resulting in a total of 14 linear steps from readily available materials.
Article Abstract
A stereoselective synthesis of the bis-guanidinium toxin (+)-saxitoxin (STX), the agent infamously associated with red tides and paralytic shellfish poisoning, is described. Our approach to this unique natural product advances through an unusual nine-membered ring guanidine intermediate 39 en route to the tricyclic skeleton that defines STX. The effectiveness of this strategy is notable, as only four steps are needed to transform 39 into the target molecule, including a four-electron alkene oxidation catalyzed by OsCl3. Construction of the critical monocyclic guanidine has been achieved through two channels, the first of which makes use of Rh-catalyzed C-H amination and highlights a novel class of heterocyclic N,O-acetals as iminium ion equivalents for crafting functionalized amines. A second route to 39 relies on a stereoselective acetylide dianion addition to a serine-based nitrone, thereby facilitating the preparation of STX in just 14 linear steps from commercial material.
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| http://dx.doi.org/10.1021/ja071501o | DOI Listing |
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