REDUCTIVE AMINATION USING POLY(ETHYLENE GLYCOL) ACETALDEHYDE HYDRATE GENERATED IN-SITU - APPLICATIONS TO CHITOSAN AND LYSOZYME

Covalent linkage of poly(ethylene glycol) (PEG) to drug molecules resu lts in water-soluble conjugates with altered bioavailability, pharmaco kinetics, Immunogenic properties, and biological activities. For drugs bearing one or more amino groups, reductive amination is a potentiall y useful method for conjugation to PEG. PEG acetaldehyde has been used for this purpose, but its ease of polymerization under certain condit ions and its susceptibility to air oxidation have caused some problems in its application. A simple and reliable method for preparation and use in reductive amination of PEG acetaldehyde hydrate generated in si tu by hydrolysis of PEG acetaldehyde diethylacetal is demonstrated. PE G acetaldehyde diethylacetal is prepared in high yield and purity by r eaction of PEG with chlorodiethylacetal in dioxane in the presence of finely powdered sodium hydroxide under heterogeneous conditions. PEG a cetaldehyde hydrate is generated in solution by hydrolysis in aqueous acids. Solutions of the hydrate may be used directly, in conjunction w ith sodium cyanoborohydride, to effect reductive amination. We demonst rate application of these methods in PEGylation of lysozyme and chitos an to form water-soluble methoxy poly(ethylene glycol) (mPEG) derivati ves and PEG-chitosan hydrogels.