Synthesis and polymerization of carbamate-linked cyclodextrin methacrylate monomers

A one-step synthesis for cyclodextrin methacrylate monomers was examined starting from alpha-, beta- and gamma-cyclodextrin. The reaction of 2-isocyanatoethyl methacrylate as well as allylisocyanate with the corresponding cyclodextrin gave the monofunctionalized carbamate-linked cyclodextrin methacrylates 2, 6 and 9 and allylcarbamates 11 and 14 in moderate yields. By NMR spectroscopic means, it could be proven that in all cases only the primary 6-hydroxyl groups of the cyclodextrins reacted with the isocyanate group. For the synthesis of a beta-cyclodextrin monoallyl compound, a substitution reaction of purchasable 6-O-monotoluenesulfonyl-beta-cyclodextrin with allylamine gave 6-N-allylamino-6-deoxy-beta-cyclodextrin 18 in high yield. The reaction of 2-isocyanatoethyl methacrylate with alpha-cyclodextrin to the 6-O-carbamoyl-2-methylpropenoylethyl-alpha-cyclodextrin (2) was optimized so that the monomer 2 could be prepared on a larger scale without chromatographic separation. The aqueous radical homopolymerization of 2 with the peroxodisulfate/bisulfite redox initiator gave the water soluble cyclodextrin polymer 19 in good yield. Its molecular weight was determined by gel permeation chromatography to be M-n = 101,800 corresponding to an average degree of polymerization P-n = 90.