Synthetic and bioorganic studies on Ciguatoxin and Tetrodotoxin acting to sodium channel protein

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This research includes two major natural products conducting the ion current in the sodium channel protein ; thus, ciguatoxin and tetrodotoxin. Total synthesis of the latter has been accomplished by 2 routes initiated by Claisen rearrangement or Diels-Alder cycloaddition from 2 different sugar derivatives, respectively. These routes are different with respect to the key reactions, and thus both of them are quite useful for the further bioorganic studies. On the other hand, the synthetic studies on ciguatoxin has been culminated to a point of synthesizing Left segment, Right segment and their model coupling reaction by means of acetylene biscobalt-hexacarbonyl chemistry. The crytical step is the formation of F and G rings after the coupling step. We have developed an important reaction for conversion of the cobalt complex into the requisited ketone with regioselectivity. We have also established the catalytic amount of cobalt reagent to achieve 4 steps in one pot ; thus, complexation, hydrosylilation, cyclization and decomplexation with stereochemical control.