The present invention provides a method for preparing a 6-aminohexyl lactoside-NOTA conjugate. The preparation method comprises brominating perbenzoylated lactose with hydrobromic acid glycosylating 6-azidohexanol to obtain 6-azidohexyl perbenzoyl lactoside and deprotecting this precursor in two steps to obtain 6-aminohexyl lactoside and conjugating 6-aminohexyl lactoside to NCS-benzyl-NODA GA (i.e. 2,2-(7-(1-carboxy-4-((4-isothiocyanate benzyl) amino)-4-oxobutyl)-1,4,7-triazonane-1,4-diyl) diacetic acid) in triethyl amine as an alkaline solvent, to obtain a 6-aminohexyl lactoside-NCS-benzyl-NODA GA conjugate. In this novel preparation method, no deglycosylated side product is produced, such that the yield is considerably increased to 46%. Therefore, the method is suitable for future massive production since the requirement for repeated preparations for massive production is reduced, and the impurities produced in the previously scaled-up preparation process are not present.
