Endotoxic properties of synthetic pentaacyl lipid A precursor Ib and a structural isomer

Abstract

A pentaacyl precursor of lipid A biosynthesis, termed precursor Ib, and a structural isomer have been chemically synthesized. These compounds were, in comparison to synthetic Escherichia‐coli type lipid A or lipopolysaccharide, analyzed for their activity in typical endotoxin test systems. It was found that both precursor Ib and the isomer exhibited similar or only slightly lower pyrogenic, lethal and Shwartzman‐phenomenon‐inducing activity than lipid A. All preparations were comparable in their B‐lymphocyte mitogenicity, macrophage‐activating capacity and immunoreactivity towards lipid A antisera. The proton nuclear magnetic resonance spectra of the 1‐dephospho derivative of synthetic and bacterial precursor Ib were indistinguishable proving that the previously proposed structure for precursor Ib is correct.