Post-Polymerization Functionalization Approach for Highly Water-Soluble Well-Defined Regioregular Head-to-Tail Glycopolythiophenes

Abstract

Two bromide-bearing regioregular head-to-tail polythiophenes (polymers 1 and 3) were prepared by using Grignard metathesis method to polymerize 2,5-dibromo-3-bromohexylthiophene (2) and 2,5-dibromo-3-(11-bromo-3,6,9-trioxa-1-undecoxy)thiophene ( 7), respectively. Well-defined regioregular head-to-tail glycopolythiophenes were prepared through post-polymerization functionalization approach by treating the bromidebearing polythiophenes with 1-thiolethyl-R-D-mannose tetraacetate (3a) or 1-thiol-β-D-glucose tetraacetrate (3b) in THF solution with a basic condition, respectively, and followed by sequential deacetylation under Zemple ´n conditions in methanol and methylene chloride containing sodium methoxide at room temperature. Glycopolythiophenes (polymers C and D) with hydrophilic tetra(ethylene glycol) as tethered spacers between the polymer backbone and carbohydrate residues are highly water-soluble while glycopolythiophenes (polymers A and B) with hydrophobic hexyl tethered spacers are completely insoluble in water. All polythiophenes display low fluorescence with fluorescent quantum yield ranging from 0.4% to 3%. However, water-soluble polymers C and D in 0.1 M phosphate buffer (pH 7.2) show a little higher fluorescent intensity than their precursor polymer 3 in chloroform solution. R-Mannose-bearing glycopolythiophene (polymer C) exhibits specific binding to Concanavalin A through multivalent interactions with a binding constant of 2.15 × 10 5 .

Triphenylamine-based fluorescent conjugated glycopolymers: Synthesis, characterization and interactions with lectins

“…5). When all other variables are kept constant, the higher K SV means the lower concentration of quencher is required to quench the fluorescence [11,19,30]. These results revealed that PNA can selectively bind to polymer P-2 based on multivalent interactions.…”

“…where I 0 is the fluorescent intensity in the absence of quencher, I is the fluorescent intensity as a function of quencher concentration [Q], and K SV is the Stern-Volmer constant, defining the efficiency of quenching [11,19,30]. The Stern-Volmer quenching constant of polymer P-2 by PNA was calculated as 1.56 Â 10 5 M À1 based on the linear part of the curve (Fig.…”

“…As multivalent model systems and artificial glycoconjugates, synthetic glycopolymers have demonstrated to be important well-defined tools for investigating carbohydrate-based biological events [6][7][8]. In particular, fluorescent conjugated glycopolymers that possess both fluorescent scaffolding and reporting carbohydrate ligands are attractively used in carbohydrate-protein interaction studies and biosensor applications because of their intrinsic optical properties, high sensitivities to minor stimuli, and good biocompatibilities [9][10][11][12][13]. A few conjugated polymers, such as polythiophene [10,11], polyfluorene [12], poly(p-phenylene-ethynylene) [13][14][15][16][17], poly(phenylene-vinylene) [18], and poly(p-phenylene) [19], have been chosen to design this type of multivalent glycoconjugates.…”

“…In particular, fluorescent conjugated glycopolymers that possess both fluorescent scaffolding and reporting carbohydrate ligands are attractively used in carbohydrate-protein interaction studies and biosensor applications because of their intrinsic optical properties, high sensitivities to minor stimuli, and good biocompatibilities [9][10][11][12][13]. A few conjugated polymers, such as polythiophene [10,11], polyfluorene [12], poly(p-phenylene-ethynylene) [13][14][15][16][17], poly(phenylene-vinylene) [18], and poly(p-phenylene) [19], have been chosen to design this type of multivalent glycoconjugates. One approach to such a system is represented by the polymerization or copolymerization of well-defined carbohydrate-carrying monomers through classical C-C coupling reactions [10,13,[15][16][17][18].…”

“…One approach to such a system is represented by the polymerization or copolymerization of well-defined carbohydrate-carrying monomers through classical C-C coupling reactions [10,13,[15][16][17][18]. Another synthetic approach is the so-called postpolymerization functionalization, in which sugar moieties are grafted to the backbones after the formation of conjugated polymers [11,12,14,19].…”