Properties of di(triethylene glycol monomethyl ether) squarate (1) relevant to conjugation of carbohydrates to proteins were reinvestigated and compared with those of dimethyl squarate (2). Using 1 and 2 as reagents, two squarate derivatives of linker-equipped lactose, 3 and 4, were prepared. The hydrolytic stabilities of 3 and 4 were compared in two different buffers (0.5 M pH 9 buffer and 0.01 M pH 9.5 buffer). The conjugation reactions of 3 and 4 with BSA in the two buffer systems were also evaluated. It was concluded that the commercially available, crystalline dimethyl squarate 2 remains the most convenient and most efficient reagent for conjugation of amine-containing carbohydrates to proteins by a two-step or one-pot conjugation protocol.

Conjugation of carbohydrates to proteins using di(triethylene glycol monomethyl ether) squaric acid ester revisited

256th National Meeting (2018)

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