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1
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DALDA analogues containing α-hydroxymethylamino acids.

100%
Olma A., Chung N. N., Schiller P. W., Zabrocki J.
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2001
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vol. 48
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issue 4
1121-1124
EN
To evaluate the role of aromatic amino-acids residues, four analogues of the μ-selec-tive opioid peptide agonist DALDA (H-Tyr-D-Arg-Phe-Lys-NH2) containing the amphiphilic, α,α-disubstituted amino acid (R)- or (S)-α-hydroxymethyltyrosine (HmTyr) in position 1 and (R)- or (S)-α-hydroxymethylphenylalanine (HmPhe) in position 3 of the peptide sequence were synthesized. Only the [(R)-HmPhe3)]DALDA analogue displayed full agonistic activity in both the guinea pig ileum and the mouse vas deferens assays and turned out to be a δ receptor-selective opioid agonist.
2
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Cyclic dermorphin tetrapeptide analogues obtained via ring-closing metathesis

88%
Berezowska I., Chung N. N., Lemieux C., Wilkes B. C., Schiller P. W.
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2006
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vol. 53
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issue 1
73-76
EN
The dermorphin-derived cyclic tetrapeptide analogues H-Tyr-c[d-Cys-Phe-Cys]NH2 and H-Tyr-c[d-Cys-Phe-D-Cys]NH2 are opioid agonists at the µ and δ receptor. To enhance the metabolic stability of these peptides, we replaced the disulfide bridge with a bis-methylene moiety. This was achieved by solid-phase synthesis of the linear precursor peptide containing allylglycine residues in place of the Cys residues, followed by ring-closing metathesis. In the case of the peptide with L-configuration in the 4-position both the cis and the trans isomer of the resulting olefinic peptides were formed, whereas the cis isomer only was obtained with the peptide having the d-configuration in position 4. Catalytic hydrogenation yielded the saturated -CH2-CH2- bridged peptides. In comparison with the cystine-containing parent peptides, all olefinic peptides showed significantly reduced µ and δ agonist potencies in the guinea pig ileum and mouse vas deferens assays. The -CH2-CH2-bridged peptide with l-configuration in the 4-position was equipotent with its cystine-containing parent in both assays, whereas the bis-methylene analogue with d-configuration in position 4 was 10-27-fold less potent compared to its parent. The effect of the disulfide replacements with the -CH=CH- and-CH2-CH2- moieties on the conformational behavior of these peptides was examined by theoretical conformational analysis which provided plausible explanations in terms of structural parameters for the observed changes in opioid activity.
3
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Dansylated analogues of the opioid peptide [Dmt1]DALDA: in vitro activity profiles and fluorescence parameters.

88%
Berezowska I., Lemieux C., Chung N. N., Zelent B., Schiller P. W.
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vol. 51
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issue 1
107-113
EN
Dansylated analogues of the potent and selective μ opioid peptide agonist [Dmt1]DALDA (H-Dmt-D-Arg-Phe-Lys-NH2; Dmt = 2',6'-dimethyltyrosine) were prepared either by substitution of Nβ-dansyl-α,β-diaminopropionic acid or Nε-dansyllysine for Lys4, or by attachment of a dansyl group to the C-terminal carboxamide function via a linker. All three analogues displayed high μ agonist potency in vitro and the C-terminally dansylated one retained significant μ receptor selectivity. The three analogues showed interesting differences in their fluorescence emission maxima and quantum yields, indicating that the dansyl group in two of them was engaged in intramolecular hydrophobic interactions. These dansylated [Dmt1]DALDA analogues represent valuable tools for binding studies, cellular uptake and intracellular distribution studies, and tissue distribution studies.
4
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A novel cis-peptide bond motif inducing β-turn type VI. The synthesis of enkephalin analogues modified with 4-aminopyroglutamic acid.

88%
Kaczmarek K., Kaleta M., Chung N. N., Schiller P. W., Zabrocki J.
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2001
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vol. 48
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issue 4
1159-1163
EN
A new pathway leading to a mixture of four isomers of 4-aminopyroglutamic acid is described. Michael type addition of Z-ΔAla-OMe to enolates prepared from acylaminomalonates, followed by hydrolysis and decarboxylation give protected 4-aminopyroglutamic acid with the 4-aminopyroglutamic acid with the cis:trans ratio approximately 3:2. This mixture was incorporated into Leu-enkephalin (position 2-3). After separation of peptides it appeared that all analogues were essentially inactive in guinea pig ileum and mouse vas deferens bioassays.
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