The synthesis of a trisaccharide (common to glycoform I and II) and a tetrasaccharide (common to glycoform I) from the outer core domain of Pseudomonas aeruginosa lipopolysaccharide (LPS) using a novel hydroquinone-based reducing-end capping group is reported. This multifunctional capping group was utilized as purification handle and was stable toward many common transformations in oligosaccharide synthesis. The access to outer-core LPS antigens with a TBDPS-protected hydroquinone (TPH) at the reducing end will be useful for glycan array and therapeutic glycoconjugate synthesis.