Synthesis of 3‑Deoxy‑l‑ketohexoses through Group Transfer

A practical method for the synthesis
of 3-deoxy-l-ketohexoses
is described. Both d- and l-ketohexoses can be transformed
into rare 3-deoxy-l-ketohexoses in six steps through a group
transfer process. The key step involves a radical cyclized onto a
carbonyl group, followed by a fragmentation reaction, eventually resulting
in the group transfer of an α-oxy carbonyl group. The process
involves tin-free and environmentally benign radical conditions (TTMSS/AIBN/toluene).
The acyclic form of 3-deoxy-l-fructose was prepared in only
three steps from the inexpensive starting material, d-fructose.
A further modification by preparing a dithioacetal derivative was
accomplished, which could serve as a convenient sugar synthon for
further synthetic applications. Removal of the dithioacetal protecting
group results in the formation of the rare 3-deoxy-l-fructose
in a total yield of 42%. This methodology could be further extended
to the synthesis of other deoxy-l-ketohesoses, such as 3-deoxy-l-sorbose.