Absolute configuration at C45 in 45-hydroxyyessotoxin, a marine polyether toxin isolated from shellfish

Sulfonyl-stabilized oxiranyllithium-based approach to polycyclic ethers. Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin

Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin, marine polycyclic ether toxins causative of diarrheic shellfish poisoning, has been accomplished. The A-ring fragment was constructed by coupling of an appropriately functionalized sulfonyl-stabilized oxiranyl anion and a triflate prepared from an erythritol derivative. An iterative protocol of the oxiranyl anion strategy was also applied for the construction of the DEF-ring fragment. The triflate derivatives of the A-ring and the DEF-ring fragments were connected with lithium acetylide. The resulting acetylene derivative was further transformed into the hexacyclic ABCDEF fragment via oxidation of the acetylene unit to 1,2-diketone, double methyl acetal formation, and reductive etherification.

Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin

[formula: see text] The convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin was accomplished. This efficient convergent strategy was performed on the basis of the coupling of the acetylide of the A-ring and the triflate of the DEF-ring, oxidation of the alkyne to diketone, intramolecular diacetalization, and stereoselective reduction of the diacetal with Et3SiH-TMSOTf.

The chemistry and biological function of natural marine toxins

Studies on ciguatera fish poisoning led to clarification of the absolute stereochemistry of ciguatoxin, gambierol, gambieric acids, and maitotoxin. Anisotropic NMR reagents and fluorometric chiral HPLC reagents were effectively used together with synthesis of partial structures. Structures of 16 ciguatoxin congeners were successfully elucidated by FAB/MS/MS using samples of 5 microg or less. Stereochemical assignments were also achieved on dinophysistoxin-1, pectenotoxins, yessotoxins, polycavernoside-A, azaspiracid, and prymnesins. The toxins possessed poly-cyclic-ether structures and originated from unicellular algae. Biological functions are briefly described.