Synthesis of BODIPY-Labeled Cholesterylated Glycopeptides by Tandem Click Chemistry for Glycocalyxification of Giant Unilamellar Vesicles (GUVs).

The glycocalyx cover membrane surfaces of all living cells. These complex architectures render their interaction mechanisms on the membrane surface difficult to study. Artificial cell-sized membranes with selected and defined glycosylation patterns may serve as a minimalistic approach to systematically study cell surface glycan interactions. The development of a facile general synthetic procedure for the synthesis of BODIPY-labeled cholesterylated glycopeptides, which can coat cell-size giant unilamellar vesicles (GUVs), is described. These peptide constructs were synthesized by: 1) solid-phase peptide synthesis (SPPS) using cholesterylated Fmoc-amino acids (Fmoc=9-fluorenylmethoxycarbonyl) followed by tandem click reactions, 2) attachment of a BODIPY-bicyclononyne (BCN) (prepared by Mitsunobu chemistry via novel aryl BCN-ethers) in the absence of a catalyst, and 3) glycosylation by means of copper(I)-catalyzed click reaction of an azidoglycan. Seven different GUV-glycoforms were prepared and four of these were evaluated with their corresponding four specific anti-glycan binding lectins.