Note: The archetypical (Enterobacteriaceae) structure of lipid A consists of a \(\beta\)-1,6-linked d-glucosamine (GlcN) or 2,3-diamino-2,3-dideoxy-d-glucose (GlcN3N) disaccharide (or a mixture of them), which is acylated by varying numbers (usually four to seven) of ester- and amide-linked acyl groups (often termed primary and secondary fatty acids). Phosphate groups and other glycosyl substituents may be linked at the \(\ce{C-1}\) and \(\ce{C-4^{\prime}}\) positions. Lipid A is linked to the core oligosaccharide at the \(\ce{C-6^{\prime}}\) position of the distal sugar unit of lipid A.