Action of Molybdate\nAnion on d‑Glucosone:\nCatalytic Conversion to Aldonates Involving C1–C2 Transposition

Treatment of the osone (aldos-2-ulose), d-[1-<sup>13</sup>C]glucosone (<b>1</b><sup>1</sup>), with sodium molybdate\nat\n90° for 30 h gave a mixture of d-[2-<sup>13</sup>C]gluconate\n(<b>2</b><sup>2</sup>) and d-[2-<sup>13</sup>C]mannonate\n(<b>3</b><sup>2</sup>) in an 85:15 ratio, indicating that the\nreaction proceeds with C1–C2 transposition similar to that\nobserved previously with aldoses. Reactions with several singly and\ndoubly <sup>13</sup>C-labeled isotopomers of <b>1</b> confirmed\nthis transposition. In contrast to the aldose reaction, the reaction\nwith <b>1</b> is irreversible, presumably due to electrostatic\nrepulsion between the negatively charged catalytically active bimolybdate\nspecies and the negatively charged aldonate product. The production\nof <b>2</b> and <b>3</b> is mediated by the formation\nof two structurally distinct bimolybdate complexes, one producing\nthe <i>gluco</i> isomer and the other producing the <i>manno</i> isomer. Reaction byproducts were also observed, specifically d-[1-<sup>13</sup>C]arabinose (<b>4</b><sup>1</sup>) and\n[<sup>13</sup>C]formate (<b>5</b>), when <b>1</b><sup>1</sup> was used as the reactant. These byproducts appear to form\nfrom the breakdown of bimolybdate complexes via alternative pathways\nthat compete with those responsible for aldonate formation.