Exhaustive glycosylation, pegylation, and glutathionylation of a [G4]-ene48 dendrimer via photoinduced thiol-ene coupling

The use of free-radical thiol-ene coupling (TEC) for the introduction of carbohydrate, poly(ethylene glycol), and peptide fragments at the periphery of an alkene functional dendrimer has been reported in this article. Four different sugar thiols including glucose, mannose, lactose, and sialic acid, two PEGylated thiols, and the natural tripeptide glutathione were reacted with a fourth generation alkene functional dendrimer [G4]-ene48 on irradiation at λmax 365 nm. In all cases, the 1H NMR spectra of the crude reaction mixture revealed the complete disappearance of alkene proton signals indicating the quantitative conversion of all 48 alkene groups of the dendrimer. With one exception only, all dendrimer conjugates were isolated in high yields (70-94%), validating the high efficiency of multiple TEC reactions on a single substrate. All isolated and purified compounds were analyzed by matrix assisted laser desorption ionization-time of flight (MALDI-TOF) spectrometry and gave spectra consistent with the assigned structure. © 2011 Wiley Periodicals, Inc.