Benz[f]isoquinoline analogues as high-affinity sigma ligands

Gold-catalysed regioselective cascade cycloisomerisation reactions of aza-enediynes for the synthesis of substituted benzoisoquinoline derivatives

A facile, regioselective, gold-catalysed cascade cycloisomerisation of easily assembled aza-enediynes to afford dihydrobenzo[f]isoquinoline derivatives is reported.

Synthetic routes to benzosuberone-based fused- and spiro-heterocyclic ring systems

Benzosuberones are an important class of medicinal and pharmaceutical compounds and have recently attracted considerable attention. The present review highlights the progress in the synthesis of benzosuberones and their fused and spiro ring systems up to 2015.

Design, synthesis, and evaluation of hexahydrobenz[f]isoquinolines as a novel class of dopamine 3 receptor ligands

We previously identified hexahydrobenz[f]isoquinoline (4a) as a new class of dopamine 3 receptor (D(3)) ligand. Herein, we described the design, synthesis, and preliminary structure-activity relationships of new analogues of 4a as a novel class of D(3) ligands. Among these new analogues, compound 4 h is a potent D(3) ligand (K(i)=6.1 nM) and has a selectivity of 133-fold between D(3)- and D(2)-like receptors, and of 163-fold between D(3)- and D(1)-like receptors, respectively. Thus, compound 4 h represents a promising new lead compound for further design and optimization toward achieving highly potent and selective D(3) ligands.

Design, synthesis, structure-activity relationships, and biological characterization of novel arylalkoxyphenylalkylamine sigma ligands as potential antipsychotic drugs

sigma Receptor antagonists may be effective antipsychotic drugs that do not induce motor side effects caused by ingestion of classical drugs such as haloperidol. We obtained evidence that 1-(2-dipropylaminoethyl)-4-methoxy-6H-dibenzo[b,d]pyran hydrochloride 2a had selective affinity for sigma receptor over dopamine D2 receptor. This compound was designed to eliminate two bonds of apomorphine 1 to produce structural flexibility for the nitrogen atom and to bridge two benzene rings with a -CH2O- bond to maintain the planar structure. In light of the evidence, N, N-dipropyl-2-(4-methoxy-3-benzyloxylphenyl)ethylamine hydrochloride 10b was designed. Since compound 10b had eliminated a biphenyl bond of 6H-dibenzo[b,d]pyran derivative 2a, it might be more released from the rigid structure of apomorphine 1 than compound 2a. The chemical modification of compound 10b led to the discovery that N, N-dipropyl-2- [4-methoxy-3-(2-phenylethoxyl)phenyl]ethylamine hydrochloride 10g (NE- 100), the best compound among arylalkoxyphenylalkylamine derivatives 3, had a high and selective affinity for sigma receptor and had a potent activity in an animal model when the drug was given orally. We report here the design, synthesis, structure-activity relationships, and biological characterization of novel arylalkoxyphenylalkylamine derivatives 3.

Derivation of a three-dimensional pharmacophore model of substance P antagonists bound to the neurokinin-1 receptor

Constrained systematic search was used in an exhaustive conformational analysis of a structurally diverse set of substance P (SP) antagonists to identify a unique hypothesis for their bound conformation at the neurokinin-1 receptor. In this conformation, two aromatic groups essential for high affinity adopt a perpendicular or edge-on arrangement. This pharmacophore hypothesis for the receptor-bound conformation was used in a comparative molecular field analysis (CoMFA) of an expanded set of SP antagonists, and the predictive ability of the resulting three-dimensional quantitative structure-activity relationship (3D-QSAR) was evaluated against a test set of SP antagonists different from those in the training set. This CoMFA model based on the Constrained Search alignment yielded significant cross-validated, conventional, and predictive r2 values equal to 0.70, 0.93, and 0.82, respectively. For comparison, the SP antagonists were forced into an alternative poorer alignment in which the two aromatic rings were parallel and then subjected to a CoMFA analysis. Both the parallel and perpendicular arrangements of the aromatic rings are seen in X-ray structures of SP antagonists and have been proposed as candidates for the receptor-bound conformation. The parallel (or stacked) conformation yielded a poorer correlation with a cross-validated r2 = 0.57, a conventional r2 = 0.90, and a predictive r2 = 0.78. Our results indicate that although both alignments could generate a reasonable CoMFA correlation, the stacked conformation is unlikely to be the receptor-bound conformation, as the covalent structure of the antagonists precludes a common geometry in which the aromatic rings are stacked.

Conformational analysis of three NK1 tripeptide antagonists: a proton nuclear magnetic resonance study

Two new peptides, tailored after Ac-Thr-D-Trp(CHO)-Phe-NMeBzl (TRI), namely, Ac-Thr-D-Trp(CHO)-Phe-NMe alpha MeBzl (TRA) and Ac-Thr-D-Trp(CHO)-Oic-NMeBzl (TOI), in which Phe is replaced by (3aS, 7aS)-octahydroindole-2-carboxylic acid, proved more potent and selective NK1 antagonists. The conformational properties of all three compounds were investigated in solution by NMR spectroscopy and those of TRI analyzed in greater detail by means of systematic computer-assisted modeling. All conformers whose energy differs by less than 9 kcal/mol from the absolute minimum are different from the conformer proposed in a previous molecular modeling study by the discovers of TRI. Parallel calculations for TRA and TOI yield low-energy conformers similar to those of TRI but in a slightly different order. Comparison of the shapes of low-energy conformers of all three peptides with those of four typical rigid NK1 antagonists shows that putative bioactive conformations are indeed present in solution.

N-heteroaryl-2-phenyl-3-(benzyloxy)piperidines: a novel class of potent orally active human NK1 antagonists

The preparation of a series of N-heteroarylpiperidine ether-based human NK1 antagonists is described. Two of the compounds 3-[-(2S,3S)-3-(((3,5-bis(trifluoromethyl)phenyl)methyl)oxy)- 2-phenylpiperidino}methyl]-1,2,4-triazole (11) and 5-[¿(2S,3S)-3-(((3,5-bis(trifluoromethyl)-phenyl)methyl)oxy)-2- phenylpiperidino}methyl]-3-oxo-1,2,4-triazolone (12)), in particular, are orally bioavailable and exhibited significant improvements in potency, both in vitro and in vivo, over the lead (carboxamidomethyl)piperidine ether 1. Rat liver microsome studies on a selected number of compounds from this series show the triazolone heterocycle to be considerably more stable than the others. Furthermore, both 11 and 12 have been profiled in a number of assays that may be predictive of the clinical utility of substance P antagonists.

Heterocyclic amino alcohols related to ifenprodil as sigma receptor ligands: binding and conformational analyses

The interaction of a novel series of heterocyclic amino alcohols with the sigma receptor site was assessed using radioligand binding and computerized molecular modelling. All heterocyclic amino alcohols, like the structurally related ifenprodil, fully inhibited the specific binding of [3H]R(+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ([3H]3-PPP) to rat cerebral cortical membranes. All compounds recognised two populations of binding sites labelled by [3H]3-PPP and the proportion of sites in the high affinity state was 60-80% of the total sites. Some of the heterocyclic amino alcohols also displayed similar affinity for alpha 1-adrenoceptors labelled by [3H]prazosin, where the pattern of inhibition appears to be stereospecific, unlike that seen with the binding of [3H]3-PPP. The amino alcohols had negligible affinity for sites labelled by the N-methyl-D-aspartate channel ligand, [3H]-(N-1-[thienyl]cyclohexyl)piperidine. Quantitative conformational analyses indicated that the heterocyclic amino alcohols and ifenprodil fitted well to a sigma receptor site model; low energy conformers could be superimposed like other potent sigma receptor ligands with confidence to the sigma receptor model. Our results define a new class of sigma receptor ligands and extend the understanding of the molecular requirements for drugs active at the sigma receptor.