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Updated: Jun 9, 2025

Activation and Conjugation of Soluble Polysaccharides using 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate CDAP
Published on: June 14, 2021
Serendipitous Conversion of an Acetylamino Dideoxy-Octonic Acid Derivate into a Functionalized Carbohydrate-Pyrazole
Jelena K Berl1, Christian Czaschke1, Ann-Kathrin Pramor1
1Department of Chemistry, Institute for Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany.
Abstract:
By treatment of the peracetylated methylester of 4-acetylamino-2,4-dideoxy-d-glycero-d-galacto-octonic acid (ADOA-PAE) with nitrosyl tetrafluoroborate, a serendipitous formation of a highly functionalized carbohydrate-pyrazole conjugate was observed in 95% yield. This observation is remarkable, as it involves a five-step one-pot synthesis that proceeds via an 1,3-acyl shift and a 1,5-electrocyclization, which usually requires thermal conditions; however, the reaction occurred at a temperature of 0 °C. Additionally, the excellent yield of the carbohydrate-decorated pyrazole and the regiospecificity of the cyclization are of particular interest, as regioselectivity is always a challenge in pyrazole synthesis. Subsequently, this novel access to pyrazoles starting from N-acetyl-allyl amides via nitrosation and electrocyclization was investigated. In addition, mechanistic studies for the formation of substituted pyrazoles of type were carried out.
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