M. José Morcillo

Benzimidazole derivatives. Part 1: Synthesis and structure–activity relationships of new benzimidazole-4-carboxamides and carboxylates as potent and selective 5-HT4 receptor antagonists

New benzimidazole-4-carboxamides 1-16 and -carboxylates 17-26 were synthesized and evaluated for binding affinity at serotonergic 5-HT4 and 5-HT3 receptors in the CNS. Most of the synthesized compounds exhibited moderate-to-very high affinity (in many cases subnanomolar) for the 5-HT4 binding site and no significant affinity for the 5-HT3 receptor. SAR observations and structural analyses (molecular modeling, INSIGHT II) indicated that the presence of a voluminous substituent in the basic nitrogen atom of the amino moiety and a distance of ca. 8.0 A from this nitrogen to the aromatic ring are of great importance for high affinity and selectivity for 5-HT4 receptors. These results confirm our recently proposed model for recognition by the 5-HT4 binding site. Amides 12-15 and esters 24 and 25 bound at central 5-HT4 sites with very high affinity (Ki = 0.11-2.9 nM) and excellent selectivity over serotonin 5-HT3, 5-HT2A, and 5-HT1A receptors (Ki > 1000-10,000 nM). Analogues 12 (Ki(5-HT4) = 0.32 nM), 13 (Ki(5-HT4) = 0.11 nM), 14 (Ki(5-HT4) = 0.29 nM) and 15 (Ki(5-HT4) = 0.54 nM) were pharmacologically characterized as selective 5-HT4 antagonists in the isolated guinea pig ileum (pA2 = 7.6, 7.9, 8.2 and 7.9, respectively), with a potency comparable to the 5-HT4 receptor antagonist RS 39604 (pA2 = 8.2). The benzimidazole-4-carboxylic acid derivatives described in this paper represent a novel class of potent and selective 5-HT4 receptor antagonists. In particular, compounds 12-15 could be interesting pharmacological tools for the understanding of the role of 5-HT4 receptors.

First pharmacophoric hypothesis for 5-HT7 antagonism

In order to make the first contribution to the elucidation of essential structural features for 5-HT7 antagonism, a set of thirty 5-HT7 antagonists were selected from the literature. A pharmacophore model was built using Molecular Modeling studies with Catalyst program. The information contained in this model was validated with new synthesized compounds.

1-[ω-(4-Arylpiperazin-1-yl)alkyl]-3-diphenylmethylene-2,5-pyrrolidinediones as 5-HT1A receptor ligands: Study of the steric requirements of the terminal amide fragment on 5-HT1A affinity/selectivity

In the present paper, we report the synthesis and the binding profile on 5-HT1A, alpha 1 and D2 receptors of a new series of imide-arylpiperazines 3. The study of the length of the alkyl chain and the imide substructure allows us to suggest some important differences between the no-pharmacophoric sites of both 5-HT1A and alpha 1-adrenergic receptors, which could be of great importance in order to design new selective ligands.

Application of Artificial Neural Networks in QSAR of a New Model of Phenylpiperazine Derivatives1 with Affinity for 5-HT1A and αl Receptors: A Comparision of ANN Models

During the last years artificial neural networks (ANN) have been applied successfully in the QSAR field. It has been demonstrated that this new technique is often superior to the traditional Hansch approach, providing more accurate predictions. The advantage of ANN is that with the presence of hidden layers, neural networks are able to perform nonlinear mapping of the physicochemical parameters and of the corresponding biological activity.