Synthesis of a potent and selective (18)F-labeled delta-opioid receptor antagonist derived from the Dmt-Tic pharmacophore for positron emission tomography imaging

Fluorinated and [18F]fluorinated morphinan based opioid ligands

It is well documented in the literature that opioid receptors modulate a large number of physiological functions (pain perception, breathing, mood, gastrointestinal motility, etc.). Natural opiates and 4,5α-epoxymorphinan derivatives obtained by their chemical modifications, which are frequently referred to as semi-synthetic opioids, are among the most important types of opioid ligands. On the other hand, fluorinated compounds have a remarkable record in medicinal chemistry providing developmental candidates for therapeutic applications. The reasons are very similar steric impacts of hydrogen and fluorine along with the influence of substituting fluorine for hydrogen in the molecules of exogenous compounds on their lipophilicity, metabolism, conformation and other properties. This review focuses on the functionalization of 4,5α-epoxymorphinans and their derivatives via substitutions with fluorine or fluorine-containing groups in the search for improved pharmacological profile opioid ligands and 18F-containing opioid receptor radioligands for PET. These functionalizations are typically associated with substituents either at the C(3)-O, C(6)-O, and N(17) positions of the 4,5α-epoxymorphinan core or at C(7) in the thebaine based Diels-Alder type adducts. The syntheses resulted in the preparation of both single fluorinated derivatives or short sets of fluorinated derivatives and the families of fluorine-containing opioids allowing, in principle, the structure-activity relationship studies.

Endogenous opiates and behavior: 2008

This paper is the 31st consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2008 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Solid-phase synthetic strategy and bioevaluation of a labeled delta-opioid receptor ligand Dmt-Tic-Lys for in vivo imaging

A general solid-phase synthetic strategy is developed to prepare fluorescent and/or lanthanide-labeled derivatives of the delta-opioid receptor (deltaOR) ligand H-Dmt-Tic-Lys(R)-OH. The high delta-OR affinity (K(i) = 3 nM) and desirable in vivo characteristics of the Cy5 derivative 1 suggest its usefulness for structure-function studies and receptor localization and as a high-contrast noninvasive molecular marker for live imaging ex vivo or in vivo.

Further studies on lead compounds containing the opioid pharmacophore Dmt-Tic

Some reference opioids containing the Dmt-Tic pharmacophore, especially the delta agonists H-Dmt-Tic-Gly-NH-Ph (1) and H-Dmt-Tic-NH-(S)CH(CH2-COOH)-Bid (4) (UFP-512) were evaluated for the influence of the substitution of Gly with aspartic acid, its chirality, and the importance of the -NH-Ph and N(1)H-Bid hydrogens in the inductions of delta agonism. The results provide the following conclusions: (i) Asp increases delta selectivity by lowering the mu affinity; (ii) -NH-Ph and N(1)H-Bid nitrogens methylation transforms the delta agonists into delta antagonists; (iii) the substitution of Gly with L-Asp/D-Asp in the delta agonist H-Dmt-Tic-Gly-NH-Ph gave delta antagonists; the same substitution in the delta agonist H-Dmt-Tic-NH-CH2-Bid yielded more selective agonists, H-Dmt-Tic-NH-(S)CH(CH2-COOH)-Bid and H-Dmt-Tic-NH-(R)CH(CH2-COOH)-Bid; (iv) L-Asp seems important only in functional bioactivity, not in receptor affinity; (v) H-Dmt-Tic-NH-(S)CH(CH2-COOH)-Bid(N(1)-Me) (10) evidenced analgesia similar to 4, which was reversed by naltrindole only in the tail flick. 4 and 10 had opposite behaviours in mice; 4 caused agitation, 10 gave sedation and convulsions.