Hydroxy-5-nitrobenzyl Bromide Koshlands Reagent

Hydroxy-5-nitrobenzyl bromide (Koshland s reagent) 8.0. Crystallise the bromide from benzene or benzene/ligroin. C6H6 and AcOH, and very soluble in ligroin. [Beilstein 6 H 367.]... 

Spande, T. F., M. Wilchek, and B. Witkop The Reaction of Derivatives of Tryptophan, Tryptamine, and Other Indoles with 2-Hydroxy-5-nitrobenzyl Bromide (Koshland s Reagent). J. Amer. Chem. Soc. 90, 3256-3258 (1968). 

Horton, H. R. Koshland, D. E. Jr. A highly reactive coloured reagent with selectivity for the tryptophan residue in proteins 2-hydroxy-5-nitrobenzyl bromide. J. Amer. Chem. Soc. 1965, 87, 1126-1132. 

One common way to modify tryptophan residues occurs through the addition of 2-hydroxy-5-nitrobenzyl bromide (HNB). Also known as Koshland s reagent (68), this compound first alkylates the 3-position of the ring and eventually leads to the formation of a product mixture through subsequent intramolecular cyclization pathways. Fig. 6c. This reagent exhibits good tryptophan selectivity, although some levels of... 

Tryptophan cleavage with NBS can be blocked by reaction of the tryptophan peptide or protein with 2-hydroxy-5-nitrobenzyl bromide the Koshland reagent (see Section III.4.) or by ozonolysis of tryptophan residues to formylkynurenine (313, 419). These modification reactions of the indole nucleus restrict NBS cleavage to tyrosyl and histidyl peptide bonds. 

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