Abstract The known 5-(methoxycarbonyl)pentyl α-glycoside of the hexasaccharide of Vibrio cholerae O:1, serotype Ogawa 24 was newly prepared. The efficiency of construction of the hexasaccharide from the disaccharide glycosyl acceptor 6 and each of the two tetrasaccharide glycosyl donors 16, and 18, as an alternative to the iterative coupling of the disaccharide glycosyl donor 7 with 6, was evaluated. Compound 24 was treated with each of hydrazine hydrate, ethylenediamine, and hexamethylenediamine to give ligands 25, 27, and 29, respectively, equipped with different linkers. Reaction of the foregoing compounds with squaric acid diethyl ester, and the reactions of the thus formed monoesters 26, 28, and 30 with BSA were evaluated. The rate of formation of the corresponding monoester was higher with hydrazide 25 than with amines 27 and 29, whose reaction rates were virtually the same. Reactions of squaric acid derivatives 26, 28, and 30 with BSA were conducted under the same conditions (reaction temperature, ligand–BSA ratio, and concentration with respect to the hapten) and targeted for neoglycoconjugates with 24–BSA ratio of ∼5. Monitoring the conversions by SELDI-TOF mass spectrometry in conjunction with the ProteinChip® system made it possible to conduct the conjugations in controlled fashion, and to terminate the reactions when the desired carbohydrate–protein ratios were reached. Products from 26, 28, and 30, neoglycoconjugates 31–33, containing 4.9, 5.0, and 5.1 moles of 24/BSA, respectively, were obtained in 87–93% yields. When the conjugation started with the initial molar carbohydrate–protein ratio of 15:1, the final molar carbohydrate–BSA ratio reached after 14 days with ligands 26, 28, and 30 was 9.0, 11.0, and 9.1, respectively.