Synthesis of protein conjugates and analogues of N-acetylneuraminic acid

Abstract

N-Acetylneuraminic acid (1) was prepared from the salivary gland mucins of the Chinese swiftlet by an improved procedure using acidic resin hydrolysis. Compound 1 was transformed into the known acetochloroneuraminic acid (3) by a new two-step procedure. Koenigs–Knorr glycosylation of 3 followed by subsequent reductive ozonolysis of the 2-propenyl α-glycoside afforded the key aldehyde precursors 7 and 8, which were coupled to bovine serum albumin or tetanus toxoid by reductive amination. The factors influencing the extent of incorporation were investigated. A series of N-acetylneuraminic acid analogues modified at strategic functionalities were also synthesized. Keywords: sialic acid, N-acetylneuraminic acid, neoglycoproteins, bovine serum albumin, tetanus toxoid.