Action of Molybdate Anion on d-Glucosone: Catalytic Conversion to Aldonates Involving C1-C2 Transposition.

Treatment of the osone (aldos-2-ulose), d-[1-C]glucosone ( ), with sodium molybdate at 90° for 30 h gave a mixture of d-[2-C]gluconate ( ) and d-[2-C]mannonate ( ) in an 85:15 ratio, indicating that the reaction proceeds with C1-C2 transposition similar to that observed previously with aldoses. Reactions with several singly and doubly C-labeled isotopomers of confirmed this transposition. In contrast to the aldose reaction, the reaction with is irreversible, presumably due to electrostatic repulsion between the negatively charged catalytically active bimolybdate species and the negatively charged aldonate product. The production of and is mediated by the formation of two structurally distinct bimolybdate complexes, one producing the isomer and the other producing the isomer. Reaction byproducts were also observed, specifically d-[1-C]arabinose ( ) and [C]formate (), when was used as the reactant. These byproducts appear to form from the breakdown of bimolybdate complexes via alternative pathways that compete with those responsible for aldonate formation.