Synthesis and chiroptical properties of β‐1,2‐linked glycopolymers prepared by click polymerization

Abstract

AbstractThis article describes the design, synthesis, and folding behaviors of β‐1,2‐linked glycopolymers as a bioconjugate‐based foldamer. The synthesis of alkyne‐containing β‐glycosyl azides has been achieved via anomeric substitution using tetrabutylammonium azide (Bu4NN3) to 1,2‐anhydro sugar and subsequent esterification with 5‐hexynoic acid. Copper‐catalyzed alkyne‐azide 1,3‐dipolar cycloaddition of the glycosyl azide leads to the formation of β‐1,2‐linked glycopolymer alternating 4‐triazolyl butanoate and tribenzylated d‐galactose (PolyGal) or d‐glucose unit (PolyGlu). The folding and chiroptical properties of the polymers are discussed through UV–vis and CD spectroscopy and anisotropic factors of CD (gCD) values. The results suggest that PolyGal would adopt a helically folded structure in ClCH2CH2Cl (DCE) or THF. Thermal stability of the folded structure of PolyGal in less polar DCE appears to increase compared with that in THF. It is found that the folded structure of PolyGal in THF denatures to a random coil above 40°C. It is indicated that PolyGlu can possibly form the helically folded structure in DCE and adopt a random coil structure at high temperature region. In polar THF, PolyGlu does not fold the conformation at all the observed temperature region. Such phenomena suggest a special role of stereochemistry at the 4 position on the folding behaviors.