A set of new enantiopure polyhydroxylated azetidine derivatives has been prepared. The key starting materials, 3,6-dihydro-2H-1,2-oxazines, were subjected to a hydroboration-oxidation sequence to introduce the required 5-hydroxy group. Subsequent cleavage of the N-O bond with samarium diiodide, selective protection of the primary hydroxyl group, and ring closure after activation of the secondary hydroxyl group provided the protected azetidine derivatives. The efficacy of each individual step of this sequence depends on the configuration of the starting material. Three representative azetidine derivatives were converted into the deprotected polyhydroxylated azetidines which are interesting candidates as glycosidase inhibitors.