A convergent approach to the synthesis of lipid A

To accomplish the synthesis of compounds having the essential structural features of bacterial lipid A, one must assemble a glucosamine disaccharide bearing five to seven substituents (fatty acyl groups, phosphate ester groups) at specific positions. In the convergent synthesis described, a protected glycoside prepared from D-glucosamine hydrochloride serves as the common intermediate from which both halves of the lipid A structure are fashioned. The glycoside is then converted, by separate series of reactions, into precursors of the reducing half and the nonreducing half of the molecule. The coupling of these precursors yields a product that is readily processed into analogues of lipid A.