Didecyl squarate - A practical amino-reactive cross-linking reagent for neoglycoconjugate synthesis

The present paper describes the synthesis and use of the hydrophobic squaric decyl ester glycosides in neoglycoconjugate chemistry. The 2-aminoethyl glycosides of alpha-D-mannopyranose, lactose, globotriose, globotetraose, GM3, and sialyl Lewis x, as well as the 2-(2-aminoethylthio)ethyl glycoside of alpha-D-mannopyranose, beta-D-glucopyranose, and galabiose were reacted with squaric acid didecyl ester to afford the hydrophobic squaric decyl ester glycosides. These glycosides were efficient reagents for the conjugation to amino-functional microtiter plates, BSA and aminated Sepharose EAH 4B. The decyl ester moiety of the squaric decyl ester glycosides constitutes a traceless hydrophobic tag, which has the major advantage, as compared to the corresponding ethyl esters, that it enables easy purification of the glycosides with silica chromatography and that unreacted excesses glycosides from conjugation reaction mixtures can easily be recovered by means of C18 solid phase extraction.