Efficient synthesis of 5-thio-d-arabinopyranose and 5-thio-d-xylopyranose from the corresponding d-pentono-1,4-lactones

5-Thio-d-arabinopyranose (5) and 5-thio-d-xylopyranose (10) were synthesized from the corresponding d-pentono-1,4-lactones. After regioselective bromination at C-5, transformation into 5-S-acetyl-5-thio derivatives, reduction into lactols and deprotection afforded the title compounds in 49 and 42% overall yield, respectively.