The synthesis of the repeating unit of the immunogenic β-Kdo-containing exopolysaccharide produced by Burkholderia pseudomallei and bacteria of the B. cepacia complex is described. The target tetrasaccharide was synthesized via stereoselective 1,2-cis- and 1,2-trans-galactosylations and β-Kdosylation. A [3 + 1] coupling reaction between a trigalactosyl N-phenyl-2,2,2-trifluoroacetimidate donor and a Kdo acceptor has been successfully achieved for the assembly of the tetrasaccharide skeleton.