Synthesis of highly water-soluble cyclodextrin sulfonates by addition of hydrogen sulfite to cyclodextrin allyl ethers

Highly water-soluble cyclodextrin sulfonates were synthesised by the additi on of hydrogen sulfite to allyl ethers of alpha- and beta-cyclodextrin (alp ha- and beta-CD). The allyl derivatives were obtained by etherification of beta-CD with allyl bromide or 1-allyloxy-2,3-epoxypropane. In this way, it was possible to isolate 2(I)-O-allyl-beta-CD, 2(I)-O-(3-allyloxy-2-hydroxyp ropyl)-beta-CD and 6(I)-O-(3-allyloxy-2-hydroxypropyl)-beta-CD after column chromatography. Statistically polysubstituted (3-allyloxy-2-hydroxypropyl) -ethers of alpha- and beta-CD were also synthesised. The subsequent additio n of HSO3- to the terminal C-C double bonds was complete after 3 h at 120-1 40 degrees C. The allyl groups were converted to propylsulfonic acid groups . Sulfinic acids were formed as side products. The resulting cyclodextrin s ulfonates are highly water soluble and able to solubilize hydrophobic guest molecules, such as naphthalene. (C) 1999 Elsevier Science Ltd. All rights reserved.