Effect of 2',6'-dimethyl-L-tyrosine (Dmt) on pharmacological activity of cyclic endomorphin-2 and morphiceptin analogs.

Jakub Fichna, Renata Perlikowska, Anna Wyrębska, Katarzyna Gach, Justyna Piekielna, Jean Claude do-Rego, Geza Toth, Alicja Kluczyk, Tomasz Janecki, Anna Janecka

Index: Bioorg. Med. Chem. 19 , 6977-81, (2011)

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Abstract

This study reports the synthesis and biological evaluation of a series of new side-chain-to-side-chain cyclized endomorphin-2 (EM-2) and morphiceptin analogs of a general structure Tyr-c(Xaa-Phe-Phe-Yaa)NH(2) or Tyr-c(Xaa-Phe-D-Pro-Yaa)NH(2), respectively, where Xaa and Yaa were L/D Asp or L/D Lys. Further modification of these analogs was achieved by introduction of 2',6'-dimethyl-L-tyrosine (Dmt) instead of Tyr in position 1. Peptides were synthesized by solid phase method and cleaved from the resin by a microwave-assisted procedure. Dmt(1)-substituted analogs displayed high affinity at the μ-opioid receptors, remained intact after incubation with the rat brain homogenate and showed remarkable, long-lasting μ-opioid receptor-mediated antinociceptive activity after central, but not peripheral administration. Our results demonstrate that cyclization is a promising strategy in the development of new opioid analgesics, but further modifications are necessary to enhance the blood-brain barrier permeability.Copyright © 2011. Published by Elsevier Ltd.