18 SYNTHETIC STUDY ON TETRODOTOXIN AND RELATED COMPOUNDS

Abstract

A stereospecific synthesis of an equivalent of 9-deoxytetrodotoxin will be discussed. The ether alcohol (6), a key intermediate in this study, was stereospecifically synthesized from readily available 5-acetyltoluhydroquinone (2) by eight steps. The ether alcohol (6) was converted to the ketone (15), which was then subjected to Baeyer-Villiger rearrangement to afford the seven membered lactone (16) quantitatively. The seven membered lactone (16) was transformed to the amine (24) by eight steps. The amine thus obtained was converted to the diacetyl guanidine derivative (27) through the N-acetyl ethylisothiourea derivative (26). From the diacetyl guanidine derivative (27), 3-formyl-9-deoxytetrodotoxin acetate (28) was synthesized by a treatment with aq. trifluoroacetic acid, followed by periodate oxidation. A method introducing a hetero atom into the C_9-position of some intermediate will be discussed together. After the ketone (15) had been brominated by pyrrolidone hydrotribromide, it was subjected to Baeyer-Villiger rearrangement to afford the seven membered lactone (30), which was then transformed to the six membered lactone (31) by ethanolic acid.