Methods of preparing polymers having terminal amine groups

Abstract

The present invention is directed to methods of preparing linear polymers such as polyalkylene oxides containing a terminal amine in high purity. One preferred method includes reacting a polyalkylene oxide such as polyethylene glycol containing a terminal azide with a phosphine-based reducing agent such as triphenylphosphine or an alkali metal borohydride reducing agent such as sodium borohydride in a solvent to reflux. The resultant polymer-amines are of sufficient purity so that expensive and time consuming purification steps required for pharmaceutical grade polymers are avoided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of U.S. patent application Ser. No. 11 / 212,901, filed Aug. 26, 2005, the contents of which are incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention relates to methods of preparing activated polymers such as polyalkylene oxides. In particular, the invention relates to methods of preparing linear polymers containing a terminal amine in high purity. BACKGROUND OF THE INVENTION [0003] The conjugation of water-soluble polyalkylene oxides with therapeutic moieties such as proteins and polypeptides is known. See, for example, U.S. Pat. No. 4,179,337, the disclosure of which is hereby incorporated by reference. The '337 patent discloses that physiologically active polypeptides modified with PEG circulate for extended periods in vivo, and have reduced immunogenicity and antigenicity. [0004] To conjugate polyalkylene oxides, the hydroxyl end-groups of the polymer must firs...

AI Technical Summary

Benefits of technology

[0017] One of the chief advantages of the present invention is that the resulting terminal amine-containing polymers such as polyalkylene oxide derivatives thereof are prepared in high purity. Thus, product contaminants, namely, the starting materials, such as mPEG-OH are not found in appreciable amounts, that is, they are found in amounts of less than about 5%, preferably less than about 2% and most preferably less than about 1%. When the preferred PEG-amines are more economically formed in high purity, the artisan can make the end product which incorporates the PEG-amine more efficiently and at lower cost. The reaction to make the PEG-amine can be forced to completion and the excess small molecule reagents can be removed by recrystallization. The efficiencies result, in part, because the separation of the desired amine-terminated polymer from the starting alcohol or reactive intermediate (e.g. tosylate) is not required. Furthermore, column chromatography based purification techniques are not required to provide the desired PEG-amine. Thus, the present invention provides highly pure PEG-amine without costly column purification.

[0018] Another advantage is the fact that the amine made from the processes described herein will not change the backbone of the PEG at all. Therefore, it will be compatible with all current and future applications for PEG amines.

Problems solved by technology

More importantly, a major disadvantage is that a significant percentage of PEG-halide becomes hydrolyzed to form PEG-OH during the concentrated aqueous ammonia treatment.

Consequently, the purity of the desired end product can decrease considerably.

The harsh conditions required for removal of the phthaloyl group and the need for intensive purification of the final product add significantly to the cost of the desired product.

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