KDO (1) is synthesized in five steps, starting from 1,2-anhydro-3,4:5,6-di-O-isopropylidene-D-mannitol (6). The epoxide 6, obtained from D-mannitol (2), reacts with Lithiated silyl dithioacetal 7, followed by acylation of the alcoholate, to the carbonate 9. Silicon-induced lactonization affords the lactone 10, which can be converted into NH4-KDO by standard deprotection procedures.