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.