Journal
CARBOHYDRATE POLYMERS
Volume 138, Issue -, Pages 244-251Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.carbpol.2015.11.070
Keywords
Mannuronic acid gamma-lactone; Conformation change; 2-Chloro-1-methylpyridinium iodide; Propylphosphonic anhydride; Alginic acid alkyl amide
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Biocompatibility and thickening properties predetermine alginates as ingredients in food, cosmetic and pharmaceutical products. Further chemical modifications are often desired for a product optimization. The introduction of hydrophobic groups can be realized by employing organic tetrabutylammonium alginate (TBA-Alg) solutions. The synthesis of alginic acid alkyl amides from TBA-Alg with 2-chloro-1-methylpyridinium iodide (CMPI) as a coupling agent, however, has so far not resulted in a high degree of amidation. The analysis of the coupling reaction revealed the formation of mannuronic acid gamma-lactone structures, which required a conformation change from C-1(4) tO C-4(1). The opening of the gamma-lactone required a high excess of butylamine. In the case of CMPI, triethylamine had to be added prior to the coupling agent in order to suppress the assumed alginic acid formation. The degrees of amidation achieved were up to 0.8, and for propylphosphonic anhydride as the coupling agent up to 1. The molecular weights of the alginic acid butyl amide were >= 35 kDa. (C) 2015 Elsevier Ltd. All rights reserved.
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