N-Chloroacyl-6-O-triphenylmethylchitosans: useful intermediates for synthetic modifications of chitosan.

An efficient synthetic route was developed for the mild chloroacylation of chitosan with different chloroacyl chlorides. Full N-chloroacylation was obtained with this procedure without any O-acylation, and products having lower degrees of substitution can also be produced. Organo-soluble 6-O-triphenylmethylchitosan was used as a starting material for the acylation reactions. The resulting N-chloroacyl-6-O-triphenylmethylchitosan intermediates were also organo-soluble and characterized by FT-IR. N-Methylpiperazine moieties were attached to make end products that were sufficiently soluble for characterization by NMR and also to prove that the present intermediates could be used for further modifications. The end products were fully characterized by 1H NMR, 13C NMR, and 2D 1H-13C heteronuclear single-quantum correlation NMR spectroscopy. The degrees of substitution were determined by 1H NMR. Molecular weight determination by GPC-LS displayed a significant degradation of the polymer. The weight-average molar masses (M(w)) of the end products ranged from 29.6 to 49.4 kDa, when the M(w) of the starting material was 144.2 kDa.