Histidine protection

The DNP derivative, prepared from 2,4-dinitrofluorobenzene is released from the nitrogen with an anionic ion exchange resin." When used for histidine protection, the DNP group has been observed to migrate to nearby [ysine residues during Fmoc cleavage. ... 

The Bum derivative has been used to protect the r-nitrogen of histidine to prevent racemization during peptide bond formation. The related 1-adamantyl-oxymethylamine has been used similarly for histidine protection. 

Effects on muscle enzymes. In addition to mentioned above 5 -lipoxigenase, tirosine hydroxilase and NO-synthase, some other enzymes are known to be affected by carnosine. Carnosine (as well as histidine) protects 3-phosphoglycerate dehydrogenase from heavy metals [6] and activates phosphorylase a and b (the former— in the acidic pH areas) [77], Stimulation of the over-all glycolytic process by the dipeptides is usually explained by their pH-buflfering capacity and protection of individual glycolytic enzymes from contaminations of heavy metals [78]. 

The phenolic hydroxyl group of tyrosine, the imidazole moiety of histidine, and the amide groups of asparagine and glutamine are often not protected in peptide synthesis, since it is usually unnecessary. The protection of the hydroxyl group in serine and threonine (O-acetylation or O-benzylation) is not needed in the azide condensation procedure but may become important when other activation methods are used. 

The dinitrophenyl group has been used to protect the imidazole — NH group in histidines (45% yield)" by reaction with 2,4-dinitrofluorobenzene and potassium carbonate. Imidazole —NH groups, but not a-amino acid groups, are quantitatively regenerated by reaction with 2-mercaptoethanol (22°, pH 8, 1 h)." The 2,4-... 

The phenacyl group is stable to HBr-AcOH, CF3COOH, and CF3S03H. It is used to protect the Tr-nitrogen in histidine in order to reduce racemization during peptide bond formation. ... 

The development and use in peptide synthesis of the 1-adamantyloxymethyl protecting group for N -histidine 28 was reported <9 CS(P1)2139>. A procedure for the regiospecific alkylation of histidine and histamine at N-l(t) via the corresponding tetrahydro oximidazo[l,5-c]pyrimidines 29 was also developed <96T5363>. 

The 2-adamantyloxycarbonyl group has been found suitable for protection of the imidazole function in histidine during peptide synthesis.[7a]... 

AR Fletcher, JH Jones, WI Ramage, AV Stachulski. The use of the MJt)-phenacyl group for the protection of the histidine side chain in peptide synthesis. J Chem Soc Perkin Trans 1, 2261, 1979. 

T Brown, JH Jones, JD Richards. Further studies on the protection of histidine side chains in peptide synthesis use of the jr-benzyloxymethyl group. J Chem Soc Perkin Trans 1, 1553, 1982. 

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