- Synthesis and antinociceptive activity of [D-Ala2]Leu-enkephalin derivatives conjugated with the adamantane moiety
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Based on the physicochemical and pharmacological properties of drugs having an adamantane skeleton, an adamantane-based moiety was evaluated as a drug carrier for poorly absorbed compounds, including peptides, active towards the central nervous system (CNS). Seven [D-Ala2]Leu-enkephalin derivatives conjugated with an adamantane-based moiety at the C-terminus or N-terminus were prepared by the solution-phase method and their biological activities were examined. The compounds derivatized at the C-terminus through an ester or amide linkage were much more lipophilic than the parent peptide and exhibited moderate in vitro opioid activity (guinea-pig ileum assay). Among them, four derivatives (1, 2, 4, 5), exhibited significant antinociceptive effects in an in vivo assay (mouse tail-pressure test) after subcutaneous administration. This result suggests that the introduction of the lipophilic adamantane moiety into [D-Ala2]Leu- enkephalin would improve the permeation of the poorly absorbed parent peptide through the blood-brain-barrier (BBB) without loss of antinociceptive effect.
- Kitagawa, Kouki,Mizobuchi, Noriko,Hama, Teruo,Hibi, Tohru,Konishi, Ryoji,Futaki, Shiroh
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p. 1782 - 1787
(2007/10/03)
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- Synthesis of 2>Leu-enkephalin and 2,D-Leu5>Leu-enkephalin with High Specific Tritiated Activity in the Leucine Residue
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2>Leu-enkephalin and 2,D-Leu5>Leu-enkephalin (DADLE) labelled with tritium in the leucine residue have been prepared.Synthesis of the precursor peptides, 2,4,5-didehydro-L-Leu5>Leu-enkephalin and 2,4,5-didehydro-D-Leu5>Leu-enkephalin, was carried out by solid-phase synthesis using Fmoc amino acid derivatives, followed by diastereoisomeric separation on HPLC.These peptides were tritiated catalytically to yield DALE with a specific activity of 5.35 TBq mmol-1 and DADLE with that of 5.43 TBq mmol-1, respectively.The distribution of tritium label was investigated by HPLC with a radioisotopic detector following acidic hydrolysis, which confirmed that the tritium label in both labelled peptides was exclusively located at the leucine residue.
- Hasegawa, Hiroshi,Shinohara, Yoshihiko,Baba, Shigeo
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p. 2641 - 2644
(2007/10/02)
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- A photoaffinity reagent to label the opiate receptors of guinea pig ileum and mouse vas deferens
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An enkephalin derivative, [D-Ala2,Leu5]enkephalin N-[(2-nitro-4-azidophenyl)amino]ethylamide, has been synthesized as a photoaffinity label for the opiate receptor. This compound retains the full biological activity of [D-Ala2,Leu5]enkephalin in guinea pig ileum and mouse vas deferens tests with IC50 values of 4.4 and 2.6 nM, respectively, and inhibits the binding of [3H]naloxone to rat brain membrane preparation with an IC50 value of 2.5 nM. Photolysis of a muscle strip of the guinea pig ileum or of the mouse vas deferens in the presence of the peptide derivative caused irreversible inhibition of electrically stimulated contractions with high efficiencies (80 and 66%, respectively), while the inhibitory effect in the dark was fully reversed by washing. This irreversible inhibition during photolysis was completely prevented by the presence of [D-Ala2,Leu5]enkephalin. These results demonstrate that {D-Ala2,Leu5]-enkephalin N-[(2-nitro-4-azidophenyl)amino]ethylamide is a prominent candidate as a photoaffinity label for the opiate receptor.
- Fujioka,Matsunaga,Nakayama,Kanaoka,Hayashi,Kangawa,Matsuo
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p. 836 - 840
(2007/10/02)
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- Phosphinyl- and Phosphinothioylamino Acids and Peptides. VI. The Protection of the Hydroxyl Function in the Tyrosine Side-chain by the Dimethylphosphinothioyl Group
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The use of the dimethylphosphinothioyl (Mpt) group for the protection of the hydroxyl function in the tyrosine side-chain was studied. N,O-Bis(Mpt)tyrosine was obtained directly by a Schotten-Baumann-type reaction of Mpt-Cl with tyrosine. The O-Mpt group was stable under acidic conditions, and it could be removed easily by alkaline hydrolysis or ester-exchange reaction. The usefulness of this new protecting group for the peptide synthesis was shown in the solid-phase synthesis of 2,L-Leu5>-enkephalin(H-L-Tyr-D-Ala-Gly-L-Phe-L-Leu-OH) and its N-allyl derivative.
- Ueki, Masaaki,Inazu, Toshiyuki
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p. 204 - 207
(2007/10/02)
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