2003/06/28 by Norio Ohyabu, Toshio Nishikawa, Minoru Isobe · 6 citations
Chemistry · Environmental Science · #Aldehyde #Aldol condensation #Aldol reaction #Chemical synthesis and alkaloids #Chemistry #Claisen rearrangement #Enantioselective synthesis #Intramolecular force #Ketone #Marine Toxins and Detection Methods #Moiety #Organic chemistry #Regioselectivity #Stereochemistry #Synthetic Organic Chemistry Methods #Total synthesis
paper · doi:10.1021/ja0342998
openalex publication_date 2003/06/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
Tetrodotoxin, a toxic principle of puffer fish poisoning, is one of the most famous marine natural products because of the complex structure having many functional groups and its potent biological activity leading to death. Since the structure elucidation in 1964, this toxin has been recognized as a formidable target molecule for total synthesis. We have recently achieved the first asymmetric total synthesis from 2-acetoxy-tri-O-acetyl-d-glucal as a chiral starting material. The highly hydroxylated cyclohexane ring was constructed by Claisen rearrangement and regioselective hydroxylations of an acetone moiety and an intramolecular directed aldol condensation of the precursor having methyl ketone with dihydroxyacetone, which was synthesized through Sonogashira coupling. Installation of nitrogen functionality was unsuccessful through an attempted Overman rearrangement. We, therefore, employed a new intramolecular conjugate addition strategy between the carbamate and unsaturated ester groups. The alpha-hydroxyl lactone moiety was synthesized through an intramolecular epoxide opening by the Z-enolate of aldehyde, which was followed by oxidation-reduction of the resulting cyclic vinyl ether. The lactone was then converted to a protected ortho ester, and then gunanidinylation was followed by cleavage of the 1,2-glycol to give the fully protected tetrodotoxin. Selection of the protective groups has finally led us to accomplish the total synthesis of tetrodotoxin in an enantiomerically pure form. All the stereogenic centers were controlled with high selectivity, and the hydroxyl groups were differently protected to discriminate for the future analogue synthesis of a bioorganic program. The synthetic tetrodotoxin was purified by ion exchange chromatography and characterized to be identical with the natural compound.