Polymer-bound reagents for the introduction of spacer-modified biotin labels

We have developed a method for the chemoselective introduction of spacer modified biotin labels into unprotected multi-functional amines. A range of novel biotin spacer conjugates attached to a polymer-bound sulfonamide anchor was prepared using established amide bond forming procedures. After chemical transformation of the attachment site by alkylation, the resulting reactive species were utilized as N-selective polymer-supported biotinylation reagents. The labeled compounds, obtained in good to excellent yield and purity, are free of residual biotin and possess a custom tailored distance from the immobilization site being especially suited for the immobilization on streptavidin-functionalized dextran layers of surface plasmon resonance detector chips. In addition, derivatives displaying a phenyl group were synthesized in order to demonstrate the versatility of the procedure for the simultaneous introduction of spacer-modified biotin and a UV-light absorbing moiety. The formation of biotin sulfoxides in the presence of in situ generated peroxides was investigated and is discussed. Our results suggest that this derivatization technique is a useful addition to the existing biotin labeling protocols.