Silvano Ronzoni

Non-peptide δ opioid agonists and antagonists

Following a flurry of medicinal chemistry activity in the late 1980s, a number of non-peptide pharmacological tools, selective for the δ opioid receptors, became available to challenge the pre-eminent position occupied by the existing peptide δ ligands. The first non-peptide δ antagonist NTI (1) represented a breakthrough in this field. Several analogues have been subsequently synthesised and are currently being used to clarify the pharmacology associated with the δ opioid receptors. The discovery of the selective δ agonists TAN-67 (50), BW373U86 (56) and SNC 80 (62) represented another step towards the understanding of the involvement of the δ opioid receptor in a number of possible pathophysiological conditions. This review addresses the recent highlights and developments that have been made by several research groups in the design of potent and selective non-peptide δ ligands. Focus has been given to the different pharmacological actions of δ agonists and antagonists. Analgesia can be considered the hi...

A new synthetic approach to 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-benzimidazol-2-one(J-113397), the first non-peptide ORL-1 receptor antagonist..

An efficient approach to 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-benzimidazol-2-one (J-113397) 1, the first non-peptide ORL-1 receptor antagonist described in literature, is outlined. After construction of the piperidine framework through Dieckmann cyclization of the Michael adduct 8 of cyclooctylmethylamine to methyl acrylate, condensation with o-phenylendiamine produced the beta-enamino ester 2, which has been conveniently used to construct the benzimidazolone substituent at C-4. Catalytic hydrogenation of intermediate 11 followed by base-promoted cis--trans isomerization of the key compound 12 led to the formation of ester 13, which was converted to the racemic title compound by LiAlH(4) reduction. The pure enantiomers were obtained by chiral preparative HPLC separation using a derivatized cellulose-based stationary phase.

Selective δ opioid receptor agonists for inflammatory and neuropathic pain

In the last decade a number of selective and potent non-peptidic agents became available to explore the usefulness of the δ-opioid receptor in modulation of pain of different origins. As a continuing effort in this field, potent and selective δ-opioid agonists based on the pyrrolomorphinan framework have been designed, synthesised and characterised biologically in our laboratories. In animal models, a selected compound of interest, SB 235863, has proved the concept that selective δ-opioid agonists may have great potential as pain relief agents in inflammatory and neuropathic pain conditions. Importantly, such a compound was free of the unwanted side effects usually associated with narcotic analgesics such as morphine.

Non-peptide δ opioid agonists and antagonists (Part II)

A continuing effort in the development of non-peptide δ opioid agonists and antagonists has been seen in the last two years. The first non-peptide δ opioid antagonist naltrindole has represented for years the starting point for the design of novel potent and selective δ opioid ligands. Several research groups are still working on the framework of this prototype and have produced a large number of new derivatives with different in vitro and in vivo pharmacological activities. The discovery of TAN-67, BW373U86 and SNC 80 stimulated other lines of research aimed at synthesising analogues with better δ opioid agonist profile and suitable in vivo activity. Chemically unrelated compounds have also been disclosed deriving from the structural comparison of previously identified ligands. These studies have given further insights about the key determinants for the selective interaction with the δ opioid receptor (DOR). The availability of these tool compounds has allowed significant progression in the understanding...

Pharmacological profiles of selective non-peptidic δ opioid receptor ligands

Abstract Several non-peptidic opioids have been synthesized recently as part of a program to develop selective δ receptor agonists. In this study, the affinities of a set of compounds for cloned δ and μ opioid receptors expressed in HEK 293 cell lines were determined by competition analysis of [3H]bremazocine binding to membrane preparations. All compounds studied exhibited high affinity and selectivity, with apparent dissociation constants in the range of 0.6–1.7 nM for the δ opioid receptor and 240–1165 nM for the μ opioid receptor. We next sought to determine which domain of the δ receptor was critical for mediating the highly selective binding by analysis of ligand affinities for μ/δ receptor chimeras. Receptor binding profiles suggested that a critical site of receptor/ligand interaction was located between transmembrane domain 5 (TM5) and TM7 of the δ receptor. Substitution of tryptophan 284, located at the extracellular surface of TM6, with lysine, which is found at the equivalent position in the μ opioid receptor, led to a spectrum of effects on affinities, depending on the ligand tested. Affinities of SB 219825 and SB 222941 were particularly sensitive to the substitution, displaying a 50-fold and 70-fold decrease in affinity, respectively. Activities of the δ receptor-selective agonists were tested in two functional assays. Brief exposure of HEK 293 cells expressing δ opioid receptors with selective ligands induced phosphorylation of MAP kinase, although the non-peptidic ligands were less efficacious than the enkephalin derivative DADL (Tyr- d -Ala-Gly-Phe- d -Leu). Similarly, chronic exposure of HEK 293 cells expressing δ opioid receptors with selective, non-peptidic ligands, with the exception of SB 206848, caused receptor down-regulation, however, the SB compounds were less efficacious than DADL.

The discovery of biaryl carboxamides as novel small molecule agonists of the motilin receptor

Optimisation of urea (5), identified from high throughput screening and subsequent array chemistry, has resulted in the identification of pyridine carboxamide (33) which is a potent motilin receptor agonist possessing favourable physicochemical and ADME profiles. Compound (33) has demonstrated prokinetic-like activity both in vitro and in vivo in the rabbit and therefore represents a promising novel small molecule motilin receptor agonist for further evaluation as a gastroprokinetic agent.

Identification of small molecule agonists of the motilin receptor

High-throughput screening resulted in the identification of a series of novel motilin receptor agonists with relatively low molecular weights. The series originated from an array of biphenyl derivatives designed to target 7-transmembrane (7-TM) receptors. Further investigation of the structure-activity relationship within the series resulted in the identification of compound (22) as a potent and selective agonist at the motilin receptor.

Pyrrolooctahydroisoquinolines as potent and selective ° opioid receptor ligands: SAR analysis and docking studies

Abstract Structure Activity Relationship and docking studies focused on the role of the non-aromatic ° address in a novel class of potent and selective ° ligands, pyrrolooctahydroisoquinolines, are discussed.