Synthesis and characterization of chitosan alkyl urea

•A series of chitosan alkyl urea derivatives were synthesized.•Amino group on chitosan was selectively converted into urea.•Methoxyformylation and amine-ester exchange were performed almost quantitatively.•Theoretical calculation showed the structure of amine affect amine-ester exchange.•Prepared ch...

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Bibliographic Details
Published in:Carbohydrate polymers 2016-07, Vol.145, p.78-85
Main Authors: Wang, Jing, Jiang, Ji-Zhou, Chen, Wei, Bai, Zheng-Wu
Format: Article
Language:English
Subjects:
Amine-ester exchange
Amines - chemistry
Chitosan
Chitosan - chemistry
Chitosan alkyl urea
Formates - chemistry
N-methoxyformylation
Theoretical calculation
Urea - analogs & derivatives
Urea - chemistry
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Summary:•A series of chitosan alkyl urea derivatives were synthesized.•Amino group on chitosan was selectively converted into urea.•Methoxyformylation and amine-ester exchange were performed almost quantitatively.•Theoretical calculation showed the structure of amine affect amine-ester exchange.•Prepared chitosan alkyl urea derivatives were fully characterized by NMR spectra. Chitosan is a versatile material employed for various purposes in many fields including the development of chiral stationary phases for enantioseparation. Chitosan alkyl urea is a kind of intermediate used to prepare enantioseparation materials. In order to synthesize the intermediates, in the present work, a new way to prepare chitosan alkyl urea has been established: chitosan was first reacted with methyl chloroformate yielding N-methoxyformylated chitosan, which was then converted to chitosan alkyl urea through amine-ester exchange reaction. With a large excess of methyl chloroformate and primary amine of low stereohindrance, the amino group in chitosan could be almost completely converted to ureido group. The as-prepared chitosan alkyl urea derivatives were characterized by IR, 1H NMR, 13C NMR,1H-1H COSY and 1H-13C HSQC NMR spectra. The chemical shifts of hydrogen and carbon atoms of glucose unit were assigned. It was found that the degree of substitution was obviously lower if cyclopropyl amine, aniline, tert-butyl amine and diethyl amine were used as reactants for the amine-ester exchange reaction. The reason was explained with the aid of theoretical calculations.
ISSN:0144-8617
1879-1344
DOI:10.1016/j.carbpol.2016.03.022