N-Acetyl group

Amide resonance within the N acetyl group competes with delocalization of the nitro gen lone pair into the ring... 

A contrasting picture is seen for chitosans. Chitosans—as considered in detail in the following Chapter—are derivatives of chitin (after an alkali extraction procedure) and are available in large quantities from the shells of crabs, lobsters and other crustaceans. Pure chitin is poly-N-acetylglucoasmine. The N-acetyl groups are de-acetylated in chitosan to an extent represented by ei-... 

While the N-acetyl group likely protects the N-terminus from the action of ami-nopeptidases and the carboxamide moiety protects the C-terminus from carboxy-peptidases, these features alone do not prevent degradation of the control peptide. 

The use of protecting groups in the synthesis was minimized by utilizing the N-picolinyl and N-acetyl groups not only as structural components of 1 but also to tune the reactivity of the intermediates. 

The scope of the deamination reaction was extended to the characterization of heparin segments containing 2-acetamido-2-deoxy-D-glucosyl residues by removing (by hydrazinolysis) the N-acetyl groups and cleaving with nitrous acid (at pH 4) the otherwise resistant segments.113,232... 

Overall, these chitinase inhibitors provide an interesting example of peptide-carbohydrate mimicry. As described above for several other systems, mimicry consists of a mixture of structurally mimetic interactions and other favorable interactions with the receptor. Of the structurally mimetic interactions, the mimicry by argifin of the N-acetyl group, and part of the pyranosyl... 

Vicibactin 7101 from a mutant strain lacks the N-acetyl groups but shows comparable siderophore activity as demonstrated by uptake studies (91). 

At all levels of theory, the N-acetyl group of N-acetyl-N-arylnitrenium ions is rotated out of the plane of the aromatic ring, although to different extents." The N-acetyl group destabilizes the ion by ca. 20 kcal/mol relative to an N-methyl substituent in comparison with the neutral amide and amine precursors. This destabilization was attributed by Ford and Herman to loss of resonance in the amide precursor on going to the nitrenium ion, not to inductive destabilization of the ion by the acyl group. 

The ionic and hydrophilic nature of the amino acids precludes their isolation from biological fluids by solvent/solvent extraction. Modification of the amino group, for example the formation of an N-acetyl group, makes solvent extraction accessible. 

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