Abstract: A reactive compound is made of modified trimannose-oligosaccharides. Methods are for preparing and using modified trimannose-oligosaccharides. The compounds and methods are for improving the characteristics of a first ligand of interest, especially in therapeutic or diagnostic applications. In particular, a reactive compound includes a trimannose core of formula 1 wherein Man1, Man2 and Man3 moieties are a first, a second and a third mannose, respectively, R1 is a linking group able to bind or binding the GlcNAc group to a first ligand of interest, R2 and R3 are monosaccharides or derivatives thereof, optionally linked to one or more additional saccharide(s). GlcNAz is an unnatural N-Azidoacetylglucosamine group able to bind or binding to a second ligand of interest different from the first ligand of interest.