Reagents Sanger

Buyuktimkin and Buyuktimkin [20] described a spectrophotometric method of assay of penicillamine and its tablets. An aqueous solution of 100 mg/mL of penicillamine was added to ethanolic 5 mM Sanger reagent (l-fluoro-2,4-dinitrobenzene), solid NaHC03, and water. The solution was diluted and heated at 70 °C for 45 min. After cooling, the solution was diluted with 3% ethanolic HC1. The absorbance of the resulting yellow complex was measured at 355 nm (molar absorptivity = 19,721). Recovery of the drug from commercial tablets was 99.1 0.7%. 

Chemical methods for determining the amino acid sequence of a peptide or protein have been developed, and the normal approach is to exploit the properties of the amino group at the Al-terminus. A long-established procedure for identifying the N-terminal amino acid is use of the Sanger reagent 2,4-dinitrofluorobenzene. This reacts with an amine by nucleophilic displacement of the fluorine. 

Benzotriazoles, for example, are accessible from o-aminoaryl-substituted triazenes after a two-step reaction sequence a nucleophilic displacement followed by cleavage/heterocyclization.35 The nucleophilic halide displacement of activated haloarenes is an indispensable tool for the synthesis of highly substituted arenes. Fluoronitroarenes in particular have served as excellent precursors in this transformation. Thus, it was appealing to combine this SNAr reaction with the flexibility of diazonium chemistry. In this case, an immobilized fluoronitrophenyl triazene would be the equivalent of the Sanger reagent. 

Fluoride ion is usually a poor leaving group because it is not very polarizable. Fluoride serves as the leaving group in the Sanger reagent (2,4-dinitrofluorobenzene), used in the determination of peptide structures (Chapter 24). Explain why fluoride works as a leaving... 

The Sanger method for N-terminus determination is a less common alternative to the Edman degradation. In the Sanger method, the peptide is treated with the Sanger reagent, 2,4-dinitrofluorobenzene, and then hydrolyzed by reaction with 6 M aqueous HC1. The N-terminal amino acid is recovered as its 2,4-dinitrophenyl derivative and identified. 

In Section 17-12A, we saw that the Sanger reagent, 2,4-dinitrofluorobenzene, is a good substrate for nucleophilic aromatic substitution. Show the product, and propose a mechanism for the reaction of the Sanger reagent with the amino acid phenylalanine. 

Dinitrofluorobenzene (CAS 70-34-8), 10% aqua (Sanger reagent) (Garcia-Perez 1978)... 

Dinitrofluorobenzene (DNFB) or Sangers Reagent has also been used for similar applications such as the analysis of amino acids and amines (32). Tt reacts with both primary and secondary amines and phenols but not with aliphatic alcohols consequently it is useful for determining phenols in the presence of aliphatic hydroxy compounds. The sensitivity realized from this reagent is similar to that obtained from the dinitrobenzoyl derivatives. 

Starting from commercially available 2-fluoro-5-nitroaniline, this anihne was diazotized and coupled to benzylaminomethylpolystyrene to give the immobilized triazene 328 (R = NO2, X = F, equivalent to Sanger reagent). After nucleophilic displacement with primary amines to furnish an anihne resin, the cleavage with trifluoroacetic acid in dichloromethane proceeds smoothly at room temperature within minutes resulting in the desired l-alkyl-5-nitro-Iff-benzotriazoles 332 in excellent yield and purities (Scheme 47). This route was successfully adopted for the synthesis of a 200-member library by means of automated synthesis (Lormann et al, 2007, personal communication). 

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