Amino-Dinitrobenzene

Sanger s reagent (Section 27.11) Thecompound l-fluoro-2,4-dinitrobenzene, used in N-terminal amino acid identification. 

The SNAr reaction followed by intramolecular cyclization provides a useful method for the preparation of heterocyclic compounds, as summarized in Ref. 1. Reaction of 1-fluoronitroben-zene or 1,2-dinitrobenzene with guanidine in hot THF followed by treatment with t-BuOK gives 3-amino-1,2,4-benzotriazene 1-oxide in good yield (Eq. 9.11).19... 

P Marfey. Determination of D-amino acids, n. Use of a bifunctional reagent 1,5-difluoro-2,4-dinitrobenzene. Carlsberg Res Commun 49, 591, 1984. 

Titanium ions can also he used as redox catalysts for the indirect cathodic reduction of nitro compounds (417). The electroreduction is carried out in an H20-H2S04/Ti(S04)2-(Pb/Cu) system at 45 80°C under 5 20Am . Nitrobenzene, dinitrobenzene, nitrotoluene, 2,4-dinitrotoluene, 2-nitro-m-xylene, nitro-phenol, 2,4-dinitrophenol, nitrophenetole, o-nitroanisole, 4-nitrochlorotoluene, ni-trobenzenesulfonic acid, and 4,4 -dinitro-stilbene-2,2 -disulfonic acid can all be reduced by this procedure to the corresponding amino compounds (418) in good yields (Scheme 146) [513-516]. Tin... 

The effect which amino functionality has on the thermal and impact sensitivity of polyni-troarylenes (Section 4.8.1.4) makes amination by VNS a method with much future potential for energetic materials synthesis. Other carbon, nitrogen, oxygen and sulfur nucleophiles can displace aromatic hydrogen examples with 1,3-dinitrobenzene and 1,3,5-trinitrobenzene are extensive. 

Lysine is an essential amino acid with an e-amino group on the side chain that can react with various food components. As known, reaction of the e-amine can render lysine nutritionally unavailable reducing the nutritional value of food. While the determination of total lysine is straightforward (it is stable to acid hydrolysis), the determination of available lysine is difficult as lysine adducts are labile to the standard acid hydrolysis. A solution to this problem consists of derivatizing the e-amino group with a chromophore such as l-fluoro-2,4-dinitrobenzene (FDNB) to form a derivate which is stable to optimized hydrolysis conditions [222]. 

Hydrcxyaminobenzene. See Aminophenol in Vol, pp A241-L to A244-R. Its expl derivs 1-Hydroxy-2-amino-4,6-dinitrobenzene or Picramic Acid and 1-Hydroxy-4-amino-2,6-dinitrobenzene or Isopicramic Acid are on pp A241-R A243-R... 

The reduction to produce azoxy compounds appears to be successful for a wide range of aromatic nitro compounds. The following compounds, however, could not be reduced 1-nitronaphthalene, m-dinitrobenzene, 3,5-dinitroben-zoic acid (although o-, m-, and p-nitrobenzoic acids were reduced smoothly), compounds containing an amino group o-, orp- to a nitro group (except sodium... 

Dinitrophenamic Acid or l-Hydroxy-2-amino-4,6-dinitrobenzene). Dark-red ndls (from ale) or pcisms(from chlf), mp 169—... 

Various procedures are used to analyze protein primary structure. Several protocols are available to label and identify the amino-terminal amino acid residue (Fig. 3-25a). Sanger developed the reagent l-fluoro-2,4-dinitrobenzene (FDNB) for this purpose other reagents used to label the amino-terminal residue, dansyl chloride and dabsyl chloride, yield derivatives that are more easily detectable than the dinitrophenyl derivatives. After the amino-terminal residue is labeled with one of these reagents, the polypeptide is hydrolyzed to its constituent amino acids and the labeled amino acid is identified. Because the hydrolysis stage destroys the polypeptide, this procedure cannot be used to sequence a polypeptide beyond its amino-terminal residue. However, it can help determine the number of chemically distinct polypeptides in a protein, provided each has a different amino-terminal residue. For example, two residues—Phe and Gly—would be labeled if insulin (Fig. 3-24) were subjected to this procedure. 

Several chemical methods have been devised for identifying the N-terminal amino acid. They all take advantage of the fact that the N-terminal amino group is free and can act as a nucleophile. The a-amino groups of all the other amino acids are part of amide linkages, are not free, and are much less nucleophilic. Sanger s method for N-terminal residue analysis involves treating a peptide with l-fluoro-2,4-dinitrobenzene, which is very reactive toward nucleophilic aromatic substitution (Chapter 23). 

The reaction is carried out by mixing the peptide and l-fluoro-2,4-dinitrobenzene in the presence of a weak base such as sodium carbonate. In the first step the base abstracts a proton from the terminal H3N group to give a free amino function. The nucleophilic amino group attacks l-fluoro-2,4-dinitrobenzene, displacing fluoride. 

When Sanger s method for N-terminal residue analysis was discussed, you may have wondered why it was not done sequentially. Simply start at the N terminus and work steadily back to the C terminus identifying one amino acid after another. The idea is fine, but it just doesn t work well in practice, at least with l-fluoro-2,4-dinitrobenzene. 

Carboxypeptidase-catalyzed hydrolysis can be used to identify the C-terminal amino acid. The N terminus is determined by chemical means. One reagent used for this purpose is Sanger s reagent, l-fluoro-2,4-dinitrobenzene (see Figure 27.9). 

The overall amino acid compositions of calf duodenal (93, 93a) and calf spleen (85) enzyme showing an excess of acidic over basic amino acids are consistent with the isoelectric point of 4.85-5.0 previously reported for the calf and chicken duodenal enzyme (81, 83). The N-ter-minal amino acid of the calf enzyme was not available for reaction with l-fluoro-2,4-dinitrobenzene in 8 M urea (93a). Calf spleen enzyme reportedly contained galactosamine and glucosamine (85) other preparations apparently have not been examined for carbohydrate. 

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