Synthesis of L-Altrose and Some Derivatives

A convenient approach to the chemical synthesis of L-altrose (1) and its 6-deoxy derivative 2 has been developed by starting from D-galactose (9) and D-fucose (10), respectively. The 5-epimerization by a Mitsunobu inversion of the open-chain D-hexoses was the key step for these routes. Furthermore, the conversion of 2 into peracetylated TDP-6-deoxy-a-L-altrose (3a) was achieved by the cycloSal approach. However, the final deacetylation led to an unexpected side-reaction resulting in the previously unknown 6-deoxy-a-L-altropyranose 1,3-cyclophosphate (4).