Amorphous water-soluble cyclodextrin derivatives: 2-hydroxyethyl, 3-hydroxypropyl, 2-hydroxyisobutyl, and carboxamidomethyl derivatives of β-cyclodextrin

The pharmaceutical usefulness of natural, crystalline cyclodextrins can be improved by chemical conversions into water-soluble, amorphous mixtures of their derivatives. Reaction of beta-cyclodextrin with 2-chloroethanol, 3-chloropropanol, isobutylene oxide, or iodoacetamide yielded the title compounds. Distributions of the substitution degree were close to symmetrical and relatively narrow. The average substitution degrees increased with the amount of alkylating reagent used in the preparation. The number of components (half-width of distribution) increased with increasing average substitution degree. Further, distributions of the substitution degree were measured in glucose derivatives after hydrolysis of 2-hydroxyethyl, 2-hydroxypropyl, and 2-hydroxyisobutyl-beta-cyclodextrin. The results show an uneven distribution of substituents around the cyclodextrins, suggesting that growth of oligoglycol side chains and/or clustering of substituents on one glucose residue occurs.