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Tyrosine protection

M Englehard, RB Merrifield. Tyrosine protecting groups. Minimization of rearrangement to 3-alkyltyrosine during acidolysis. (O-cyclohexyltyrosine) J Am Chem Soc 100, 3559, 1978. [Pg.166]

Another approach to ring closure reaction is the o-arylation of substituted phenoxide ions by o-bromobenzonitrile followed by Si02-catalysed lacto-nization. The phenoxide ions of the amino acid (S)-tyrosine, protected as A, O-diacetyl methyl ester, does not racemize under the standard SRN1 conditions and can be used to obtain the optically active benzo[c]chromen-6-one (the O-acetyl is hydrolyzed in the reaction media to furnish the phenoxide ion) (Sch. 43). Racemic dibenzopyranones are obtained by the reaction of the anion from the TV-acetyl methyl ester of (R)-hydroxyphe-nylglycine with o-bromobenzonitrile 2-cyano-4,5-dimethoxybromobenzene (65 and 79% respectively) [110]. [Pg.520]

The 2-bromobenzyloxycarbonyl [Z(2-Br)] group is very stable toward the acidic conditions commonly used in Boc chemistry. In addition, only minor amounts of rearrangement products can be detected after the final acidic cleavage from the resin. Therefore, this protection is even superior to the Bzl(2,6-Cl2) group and is now the recommended O-tyrosine protection in the synthesis of large peptide sequences using the Boc/Bzl strategy in SPPS. A crucial drawback of Z(2-Br) protection is its sensitivity to nucleophiles 30 sec in 20% piperidine in DMF).P >1... [Pg.372]

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. [Pg.229]

CF3SO3H, PhSMe, 0-25°. ° In this case O-methyltyrosine was depro-tected without evidence for O C migration, which is often a problem when removing protective groups from tyrosine. [Pg.148]

An ether that would not undergo rearrangement to a 3-alkyl derivative during acid-catalyzed removal of — NH protective groups was required to protect the phenol group in tyrosine. Four compounds were investigated (9-cyclohexyl-, (9-isobomyl-, 0-[l-(5-pentamethylcyclopentadienyl)ethyl]-, and O-isopropyltyro-sine. [Pg.155]

A comparison has been made with several other common protective groups for tyrosine, and the degree of side-chain alkylation decreases in the order Bn >... [Pg.155]

The 4-(dimethylaminocarbonyl)benzyl ether has been used to protect the phenolic hydroxyl of tyrosine. It is stable to CF3CO2H (120 h), but not to HBr/AcOH (complete cleavage in 16 h). It can also be cleaved by hydrogenolysis (H2/Pd-C). ... [Pg.159]

The Dim ester was developed for the protection of the carboxyl function during peptide synthesis. It is prepared by transesterification of amino acid methyl esters with 2-(hydroxymethyl)-l,3-dithiane and Al(/-PrO)3 (reflux, 4 h, 75°, 12 torr, 75% yield). It is removed by oxidation [H2O2, (NH4)2Mo04 pH 8, H2O, 60 min, 83% yield]. Since it must be removed by oxidation it is not compatible with.sulfur-containing amino acids such as cysteine and methionine. Its suitability for other, easily oxidized amino acids (e.g., tyrosine and tryptophan) must also be questioned. It is stable to CF3CO2H and HCl/ether. - ... [Pg.243]

An isopropyl ether was developed as a phenol protective group that would be more stable to Lewis acids than would be an aryl benzyl ether. The isopropyl group has been tested for use in the protection of the phenolic oxygen of tyrosine during peptide synthesis."... [Pg.264]

The Msib group has been used for the protection of tyrosine. It is cleaved by reduction of the sulfoxide to the sulfide, which is then deprotected with acid. Reduction is achieved with DMF-SO3/HSCH2CH2SH or Bu4N I or with SiCWTFA. ... [Pg.271]

Me2P(0)Cl, Et3N, CHCI3, 76% yield. The Dmp group was used to protect tyrosine for use in peptide synthesis. It is stable to IM HCl/MeOH, 1 MHCl/AcOH, CF3CO2H, HBr/AcOH, and H2/Pd-C. [Pg.284]

The use of backbone-modified poly (amino acids) as biomaterials was first suggested by Kohn and Langer (17) who prepared a polyester from N-protected trans-4-hydroxy-L-proline, and a poly(itiuno-carbonate) from tyrosine dipeptide as monomeric starting material (12,18). [Pg.197]

Several such polymers have by now been prepared and were found to possess a variety of interesting material properties. Tyrosine-derived poly(iminocarbonates) (see Sec. IV) would be a specific example. These polymers were synthesized by means of a polymerization reaction involving the two phenolic hydroxyl groups located on the side chains of a protected tyrosine dipeptide (12). [Pg.201]

Using the general synthetic concepts described in Sec. II, we employed tyrosine dipeptides as the monomeric starting material. After protection of the N and C termini, the reactivity of a fully protected tyrosine dipeptide (structure 2) could be expected to resemble the... [Pg.212]

FIGURE 6 Molecular structures of poIy(CTTE), poly(CTTH), and poly(CTTP), a homologous series of tyrosine-derived polymers used in a study of the effect of the C-terminus protecting group on the materials properties of the resulting polymers. Cbz" stands for the benzyloxycarbonyl group (47). [Pg.214]

In order to test the influence of the C-terminus protecting groups on the properties of the resulting polymer, the ethyl, hexyl, and palmityl esters of N-benzyloxycarbonyl-L-tyrosyl-L-tyrosine were synthesized and the corresponding polymers (poly(CTTE),... [Pg.219]


See other pages where Tyrosine protection is mentioned: [Pg.364]    [Pg.364]    [Pg.1117]    [Pg.364]    [Pg.364]    [Pg.1117]    [Pg.235]    [Pg.50]    [Pg.155]    [Pg.159]    [Pg.167]    [Pg.168]    [Pg.280]    [Pg.278]    [Pg.303]    [Pg.265]    [Pg.265]    [Pg.270]    [Pg.282]    [Pg.282]    [Pg.284]    [Pg.459]    [Pg.291]    [Pg.497]    [Pg.1153]    [Pg.1294]    [Pg.94]    [Pg.123]    [Pg.852]    [Pg.191]    [Pg.198]   
See also in sourсe #XX -- [ Pg.229 ]

See also in sourсe #XX -- [ Pg.229 ]




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