5-exo Radical Cyclization onto 3-Alkoxyketimino-1,6-anhydromannopyranoses. Efficient Preparation of Synthetic Intermediates for (−)-Tetrodotoxin

Ketoxime ethers at C3 of 1,6-anhydro-β-d-mannopyranose derivatives were found to be useful 5-exo radical traps of alkyl and vinyl radicals generated at a chain tethered to the C2 hydroxyl group, allowing advanced synthetic intermediates for (−)-tetrodotoxin to be prepared from d-mannose in good overall yield.