Addition reactions ofO-acetylated glycal esters of Kdo mono-, α-(2→8)- and α-(2→4)- linked Kdo disaccharide derivatives1a - cwith NIS in acetic acid afforded good yields oftrans-diaxial as well as minor amounts oftrans-diequatorial andcis-configured 2-O-acetyl-3-deoxy-3-iodo derivatives, which were efficiently reduced with Bu3SnH/AIBN to give the corresponding per-O-acetylated Kdo methyl ester derivatives. Similar reactions of1awith NBS or NCS furnished thetrans-diaxial 2-O-acetyl-3-bromo-3-deoxy- as well as 3-chloro-3-deoxy derivatives as the main products. Reaction of1awith NBS in aqueous MeCN provided the 2,3-trans-bromohydrin derivative11c, which upon treatment with DBU in MeCN gave the elimination product11and the α-2,3-anhydro derivative12as a suitable donor of glycosides with D-glycero-D-talo- or D-glycero-D-galactoconfiguration, respectively.