An α-D-mannose ligand equipped with a free thiol through a hydrophilic PEG3 spacer. The thiol reacts with maleimides to form stable thioether conjugates or with other thiols to form disulfide bonds; it is also compatible with thiol-gold chemistry for surface immobilization. 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.