Antitrichomonal activity of δ opioid receptor antagonists, 7-benzylidenenaltrexone derivatives

Design and synthesis of unique morphinan-type molecules: Their application to the search for the unexplored binding domain between opioid receptors and morphinan ligands

The morphinan skeleton is valued in drug discovery for its beneficial physicochemical properties and is recognized as a crucial template for opioid receptor ligands. In morphinan derivatives, it is well-established that the nitrogen atom within the piperidine ring (D-ring) interacts with the amino acid residues of the opioid receptors. This interaction is recognized as one of the crucial pharmacophores between the morphinan molecule and the opioid receptors. Consequently, the structure-activity relationships (SAR) surrounding the D-ring are not well-studied, due to concerns that structural transformations around the nitrogen at the 17-position could disrupt this interaction. In this study, we found that our novel morphinan-type ligands with a side chain containing a heteroatom positioned above the d-ring have binding affinity for the opioid receptors. These novel skeletons could provide unique templates with the desired side chain above the D-ring in the morphinan skeleton, and thus, potentially advance the SAR studies of morphinan ligands with the opioid receptors.

Unexpected Rearrangement Reactions of the 14-Aminonaltrexone Skeleton

The reaction of 14-aminonaltrexone with acetic anhydride was found to produce a range of different novel compounds between the free compound and its hydrochloride. The hydrochloride produced a compound with an acetylacetone moiety, whereas the free form produced a compound with a pyranopyridine moiety. Efforts to isolate reaction intermediates and density functional theory calculations have elucidated those formation mechanisms with both bearing the novel morphinan-type skeleton. Furthermore, a derivative with the acetylacetone moiety showed binding to opioid receptors.

Morphine alkaloids: History, biology, and synthesis

This chapter provides a short overview of the history of morphine since it's isolation by Sertürner in 1805. The biosynthesis of the title alkaloid as well as all total and formal syntheses of morphine and codeine published after 1996 are discussed in detail. The last section of this chapter provides a detailed overview of medicinally relevant derivatives of the title alkaloid.

Structure-Activity Relationship between Thiol Group-Trapping Ability of Morphinan Compounds with a Michael Acceptor and Anti-Plasmodium falciparum Activities

7-Benzylidenenaltrexone (BNTX) and most of its derivatives showed in vitro antimalarial activities against chloroquine-resistant and -sensitive Plasmodium falciparum strains (K1 and FCR3, respectively). In addition, the time-dependent changes of the addition reactions of the BNTX derivatives with 1-propanethiol were examined by ¹H-NMR experiments to estimate their thiol group-trapping ability. The relative chemical reactivity of the BNTX derivatives to trap the thiol group of 1-propanethiol was correlated highly with the antimalarial activity. Therefore, the measurements of the thiol group-trapping ability of the BNTX derivatives with a Michael acceptor is expected to become an alternative method for in vitro malarial activity and related assays.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Essential structure of orexin 1 receptor antagonist YNT-707, part V: Structure-activity relationship study of the substituents on the 17-amino group

The morphinan-type orexin 1 receptor (OX₁R) antagonists such as YNT-707 (2) and YNT-1310 (3) show potent and extremely high selective antagonistic activity against OX₁R. In the course of our studies of the essential structure of 2, we identified new scaffolds by simplification of the morphinan skeleton. However, the new chemical entities carrying the D-ring removed scaffold showed insufficient activity. To improve the activity of these derivatives, we investigated the effect of substituents mainly focused on the 17-nitrogen group. The 17-N-substituted derivatives, as well as the cyclic derivatives, were synthesized and examined the OX₁R antagonistic activity. The assay results showed the interesting relationship between the OX₁R antagonistic activity and the substituents on the 17-nitrogen: the antagonistic activity was increased as the bulkiness of 17-substituents increased. Finally, the 17-N-Boc derivative 14a showed the most potent OX₁R antagonistic activity (K_i = 14.8 nM).

Favorskii-Type Rearrangement of the 4,5-Epoxymorphinan Skeleton

The aldol condensation of naltrexone with various aryl aldehydes gives the corresponding 7-benzylidenenaltrexone derivatives in high yields. However, novel C-ring-contracted morphinan compounds were produced when 2-pyridinecarboxaldehyde or its related analogues were used as a coupling partner. The key structural feature was the existence of the tetrahydrofuran ring (4,5-epoxy ring, E-ring) of the morphinan skeleton. The time-resolved in situ IR spectroscopy of the reaction system indicated the short-lived absorption of the distorted cyclopropanone intermediate.