The lipopolysaccharide of the recombinant strain Escherichia coli F515-207, expressing the genus-specific epitope of Chlamydia lipopolysaccharide, was sequentially de-O- and de-N-acylated by mild hydrazinolysis and treatment with 4 M KOH, respectively, yielding two oligosaccharide bisphosphates which were isolated by high-performance anion-exchange chromatography and gel-permeation chromatography. Their structures were determined by chemical analysis, NMR spectroscopy, and mass spectrometry as alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcN-(1-6)-alpha-D-GlcN 1,4'-P, (tetrasaccharide bisphosphate) and alpha-Kdo-(2-8)-alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcN-(1-6 )-alpha-D-GlcN 1,4'-P2 (pentasaccharide bisphosphate).