Preparation of 2-Hydroxymethylated Aldose by the Stereospecific Rearrangement of Ketose

A simple one-stage reaction system which yields 2-C hydroxymethylated aldopentose has been investigated. Four different 2-C branched aldopentoses (2-C hydroxymethylated D-arabinose, D-ribose (Hamamelose), L-lyxose, and D-xylose) were prepared from the corresponding ketoses (D-psicose, D-fructose, L-sorbose, and D-tagatose, respectively). These branched sugars were synthesized by a similar mechanism to the 2-C epimerization of aldose using a nickel complex. It was confirmed that the isomerization of ketose to the side-branched sugar proceeded in the ternary nickel complex through a sequence of stereospecific rearrangements in the sugar. The yields were dependent upon the structure of the substrate ketose and the nickel-ethylenediamine complex. N,N′-Dialkylated cyclohexanediamines were the most suitable ligands for preparing the 2-C hydroxymethylated branched chain sugar.