Lipase catalyzed esterification of free hydroxyl groups of β-cyclodextrin and its derivatives

Abstract

Modification of hydroxyl groups of β-cyclodextrin (β-CD) and its methyl and hydroxypropyl derivatives through lipase catalyzed reaction using <i>Rhizomucor miehei (Chirazyme) </i>lipase in <i>n</i>-heptane at 50°C has been carried out with acetic, propionic, butyric, isobutyric, valeric, isovaleric, lauric, octanoic, palmitic, and stearic acids. Degree of modification is determined from ¹H NMR. Although the ratio of β-CD to organic acid employed is 1:50, 6.8 OH groups on an average are found to be modified with acetic acid, 0.38 with propionic acid and 2.43 with isobutyric acid. Heptakis-2,6-di-O-methyl-β-cyclodextrin (DMβ-CD) and hydroxypropyl-β-cyclodextrin (HPβ-CD) which are already substituted with methyl and hydroxypropyl groups, respectively show degrees of substitution to be 2.45 and 2.0 at the freely available 2-OH or 3-OH hydroxyl groups.