An α-D-mannose ligand equipped with a primary amine through a hydrophilic PEG3 spacer. The amine couples with NHS-activated esters to form stable amide bonds, providing a route to conjugate the ligand onto NHS-activated molecules and surfaces. This compound provides an α-D-mannose building block for glycoconjugate synthesis and the construction of probes for mannose-recognizing receptors and lectins, including the mannose receptor (CD206) and DC-SIGN, with relevance to immune-targeting and pathogen-recognition research.