SYNTHESIS OF BLOCK-STRUCTURED-1,4-GLUCANS BY RARE-EARTH TRIFLATE INITIATED CROP OF CYCLODEXTRIN MACROMONOMERS

摘要

Many efforts have been devoted to syntheses of block-structured-1,4-glucan derivatives as model for studying structure-property relationships. Based on the cationic ring opening polymerization of permethylated cyclodextrins (CDs) reported by Suzuki et al., we performed CROP mechanistic studies with methylated and otherwise protected CDs to build up glucan block structures. Unfortunately, the obtained block copolymers were fast degraded by competing transglycosidation. In order to achieve higher selectivity and suppress transglycosidation reactions of the polymeric product, we investigated the ability of various rare-earth metal triflates to initiate polymerisation of alkylated CD macromonomers. Reaction products were characterized by ~1H NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF-MS).