Veronique Leclerc

Synthesis and structure–activity relationships of novel naphthalenic and bioisosteric related amidic derivatives as melatonin receptor ligands

A series of N-naphthylethyl amide derivatives were synthesized and evaluated as melatonin receptor ligands. The affinity of each compound for the melatonin receptor was determined by binding studies using [2-125I]iodomelatonin on ovine pars tuberalis membrane homogenates. Structure-activity relationships led to the conclusion that naphthalene is a bioisostere of the indole moiety of melatonin. Moreover it appears that the affinity is strongly affected by the size of the substituent of the nitrogen of the amidic function. Many of these ligands give biphasic dose-response curves which suggests that there may be two melatonin receptor subtypes within the ovine pars tuberalis cells. The replacement of naphthalene by benzofuran or benzothiophene did not strongly alter the affinity for the melatonin receptor. In contrast, the benzimidazole analogue was a poor ligand. Compound 7, the naphthalenic analogue of melatonin, a selective ligand of the melatonin receptor and an agonist derivative, has been selected for clinical development.

Synthesis of nitroindole derivatives with high affinity and selectivity for melatoninergic binding sites MT(3).

The aim of this study was to synthesize selective ligands for melatoninergic subtype receptors that could elucidate the physiological role of melatonin (N-acetyl-5-methoxytryptamine, 1). So, we first investigated the role of a nitro substituent in the 4-, 6-, or 7-position of the indole heterocycle. Comparatively to melatonin, its analogues that nitrated in the 6- or 7-position (6 and 22) lose MT(3) but retain good MT(1) and MT(2) affinities, whereas the 4-nitro isomer (5) shows very high affinity (nanomolar) and selectivity for the MT(3) binding sites. N-Methylation of the indole nucleus of compound 5 potentiates these effects and affords the most potent and selective MT(3) ligand (17). The 2-iodo derivatives (12 and 10) of compounds 5 and 17 have also been synthesized to evaluate their binding profile with a view to further develop MT(3) selective radioligands.

Old and new inhibitors of quinone reductase 2.

Quinone reductase 2 is a cytosolic enzyme which catalyses the reduction of quinones, such as menadione and coenzymes Q. Despite a relatively close sequence-based resemblance to NAD(P)H:quinone oxidoreductase 1 (QR1), it has many different features. QR2 is the third melatonin binding site (MT3). It is inhibited in the micromolar range by melatonin, and does not accept conventional phosphorylated nicotinamides as hydride donors. QR2 has a powerful capacity to activate quinones leading to unexpected toxicity situations. In the present paper, we report the characterization of three QR2 modulators: melatonin, resveratrol and S29434. The latter compound inhibits QR2 activity with an IC(50) in the low nanomolar range. The potency of the modulators ranged as follows, from the least to the most potent: melatonin<resveratrol<S29434. These molecular tools might permit to explore and better understand the relationship existing between QR2 catalytic activity and the various pathological situations in which QR2 has a key role.

Design and synthesis of naphthalenic derivatives as new ligands at the melatonin binding site MT3

Naphthalenic analogs of MCA-NAT (5-methoxycarbonylamino-N-acetyltryptamine) have been synthesized and evaluated as melatonin receptor ligands. Introduction of a methoxycarbonylamino substituent at the C-7 position of the naphthalenic nucleus yields MT3 selective ligands. This selectivity can be modulated with suitable variations of the C-7 position and the acyl group on the C-1 side chain. We identified new series of compounds with affinity for the MT3 binding site in the nanomolar range, and singled out a selective ligand, (N-[2-(7-methylsulfamoyl-naphth-1-yl)ethyl]acetamide (17), with a Ki of 4.9 nM and selectivity of 1024 and 2040 versus MT1 and MT2 receptors respectively.

New melatonin (MT1/MT2) ligands: Design and synthesis of (8,9-dihydro-7H-furo[3,2-f]chromen-1-yl) derivatives

Herein we describe the synthesis of novel tricyclic analogues issued from the rigidification of the methoxy group of the benzofuranic analogue of melatonin as MT1 and MT2 ligands. Most of the synthesized compounds displayed high binding affinities at MT1 and MT2 receptors subtypes. Compound 6b (MT1, Ki=0.07nM; MT2, Ki=0.08nM) exhibited with the vinyl 6c and allyl 6d the most interesting derivatives of this series. Functional activity of these compounds showed full agonist activity with EC50 in the nanomolar range. Compounds 6a (EC50=0.8nM and Emax=98%) and 6b (EC50=0.2nM and Emax=121%) exhibited good pharmacological profiles.

Effect of oxime ether incorporation in acyl indole derivatives on PPAR subtype selectivity.

Compounds that simultaneously activate peroxisome proliferator‐activated receptor (PPAR) subtypes α and γ have the potential to effectively treat dyslipidemia and type 2 diabetes (T2D) in a single pharmaceutically active molecule. The frequently observed side effects of selective PPARγ agonists, such as edema and weight gain, were expected to be overcome by using additive PPARα activity, leading to dual PPARα/γ agonists with balanced activity for both subtypes. Herein we report the discovery, synthesis, and optimization of a new series of α‐ethoxyphenylpropionic acid bearing 5‐ or 6‐substituted indoles. The incorporation of oxime ethers on the carbonyl portion of the benzoyl group can bring the PPARα/γ potency ratio equal to or slightly greater than one, as is the case for compounds 20 c and 21 a. Compound 20 c shows high efficacy in an ob/ob mouse model of T2D and dyslipidemia, similar to that of rosiglitazone and tesaglitazar, but with a significant increase in body weight gain. In contrast, compound 21 a, less potent as a dual PPARα/γ activator than 20 c, showed an interesting pharmacological profile, as it elicits a decrease in body weight relative to reference compounds.