Glycidyl ether of naturally occurring sesamol in the synthesis of mussel-inspired polymers

The objective of this work is to synthesize the mussel-mimicking ionic polymers bearing electron-rich 1,3,4-triphenoxy motifs of naturally occurring sesamol [3,4-(methylenedioxy)phenol] I. To our knowledge, the work would represent, for the first time, the ring-opening reaction of epoxide built upon the triphenoxy motifs of hydroxyhydroquinone. Sesamol I upon O-alkylation using epibromohydrin has been converted to its epoxy monomer II in 77% yield. Monomer II under ring-opening polymerization using basic Bu₄NOH and Bu₄NF as well as by Lewis acid initiator/catalyst MePh₃PBr/ⁱBu₃Al led to polyether III in 80–99% yields. Monomer II and allyl glycidyl ether (i.e. allyl 2,3-epoxypropyl ether) IV upon polymerization gave random copolymer V of number average molar mass of 9570 g mol⁻¹, which upon thiol-ene reaction with HSCH₂CH₂NH₃⁺Cl⁻ and HSCH₂CO₂H afforded cationic (^^^NH₃⁺) VI and anionic (^^^CO₂⁻) VII copolymers, respectively. For facile deprotection, the methylenedioxy (–OCH₂O–) motifs in VI was activated by its conversion to labile acetoxymethylenedioxy [–OCH(OAc)O–] unit to obtain VIII in 80% yields. The pendant allyl groups in VIII upon elaboration via thiol-ene reaction using cysteamine hydrochloride and subsequent hydrolysis of [–OCH(OAc)O–] under a mild condition led to a mussel-inspired cationic copolymer IX (78%) having catechol motifs-embedded pendants of 3,4-dihydroxyphenoxy groups.