Claudia Sorbi

1,3-Dioxolane-Based Ligands as Rigid Analogues of Naftopidil: Structure–Affinity/Activity Relationships at α1 and 5-HT1A Receptors

Conformational restriction of naftopidil led to the discovery of a new class of ligands with a 1,3‐dioxolane (1,3‐oxathiolane, 1,3‐dithiolane) structure that bind to α1 adrenoceptor subtypes and 5‐HT1A receptors. Adequate structural modifications address the selectivity toward one or the other receptor system.

1,3-Dioxolane-based ligands incorporating a lactam or imide moiety: Structure–affinity/activity relationship at α1-adrenoceptor subtypes and at 5-HT1A receptors

A series of 1,3-dioxolane-based compounds incorporating a lactam (2-4) or imide (5-7) moiety was synthesized and the pharmacological profile at alpha(1)-adrenoceptor subtypes and 5-HT(1A) receptor was assessed through binding and functional experiments. Starting from the 2,2-diphenyl-1,3-dioxolane derivative 1, previously shown to be a selective alpha(1a(A))/alpha(1d(D))-adrenoceptor subtype antagonist, over alpha(1b(B)) subtype and 5-HT(1A) receptor, and replacing one phenyl ring with lactam or imide moiety a reduction of alpha(1)/5-HT(1A) selectivity is observed, mainly due to the increase in 5-HT(1A) affinity. In functional experiments lactam derivatives seems to favour 5-HT(1A) receptor antagonism (pKb = 7.20-7.80) and alpha(1B)-adrenoceptor antagonist selectivity (alpha(1B)/alpha(1A) and alpha(1B)/alpha(1D) of about 10-fold). The most interesting of the various imide derivatives is compound 7t, which is a selective alpha(1D)-adrenoceptor antagonist (pKb = 8.1 and alpha(1D)/alpha(1A) and alpha(1D)/alpha(1B) selectivity ratios of 16 and 11 respectively) whereas at 5-HT(1A) receptor it is a potent partial agonist (pD2 = 7.98, E(max) = 60%).]. Given that cis and trans diastereomer pairs for 2-7 are possible, a computational strategy based on molecular docking studies was used to elucidate the atomic details of the 5HT(1A)/agonist and 5HT(1A)/antagonist interaction.

Discovery of a new series of 5-HT1A receptor agonists

Starting from compounds previously identified as alpha(1)-adrenoceptor antagonists that were also found to bind to the 5-HT(1A) receptor, in an attempt to separate the two activities, a new series of 5-HT(1A) receptor agonists was identified and shown to have high potency and/or high selectivity. Of these, compound 13, which combines high selectivity (5-HT(1A)/alpha(1)=151) and good agonist potency (pD(2)=7.82; E(max)=76), was found to be the most interesting.

A homology modelling-driven study leading to the discovery of the first mouse trace amine-associated receptor 5 (TAAR5) antagonists

Several recent studies have focused on a detailed analysis of the trace amine-associated receptor type 5 (TAAR5) pharmacology, up to now revealing only a limited number of species-specific ligands, which are also active towards other TAAR receptors. In this context, we developed our work on TAAR5 applying a structure-based computational protocol, revolving around homology modeling and virtual screening calculations. In detail, mTAAR5 and hTAAR5 homology models were built, in order to explore any pattern of structural requirements which could be involved in species-specific differences. Successively, the mTAAR5 model was employed to perform a virtual screening of an in-house library of compounds, including different five-membered ring derivatives, linked to a phenyl ring through a flexible or a rigid basic moiety. The computational protocol applied allowed to select a number of chemical scaffolds that were tested in a biological assay leading to the discovery of the first two mTAAR5 antagonists.

Structure–activity relationship at α-adrenergic receptors within a series of imidazoline analogues of cirazoline

Several analogues of cirazoline (2), a selective alpha1-adrenoreceptor agonist, were prepared and their pharmacological profiles studied. Although at the alpha1-adrenoreceptor all the compounds displayed a significant agonist activity, at the alpha2-adrenoreceptor they showed either agonist or antagonist activity depending on the nature of the phenyl substituent. The qualitative structure-activity relationship led us to the conclusion that the oxygen atom in the side-chain is essential for alpha1-agonist activity, while the cyclopropyl ring is not, and may be replaced by several groups. Of the groups studied, isopropoxy appears to be the best. Instead, the same substitution (i.e., isopropoxy for the cyclopropyl ring) at alpha2-adrenoreceptors causes a reversal of activity. On the other hand, the cyclopropyl ring seems to be important for alpha1-selectivity. Compound 20 is the most potent alpha1-agonist of the series, being equiactive with cirazoline on rat vas deferens and in pithed rat.

Structure-affinity/activity relationships of 1,4-dioxa-spiro[4.5]decane based ligands at α 1 and 5-HT1A receptors.

Recently, 1-(1,4-dioxaspiro[4,5]dec-2-ylmethyl)-4-(2-methoxyphenyl)piperazine (1) was reported as a highly selective and potent 5-HT1AR ligand. In the present work we adopted an in-parallel synthetic strategy to rapidly explore a new set of arylpiperazine (7-32) that is structurally related to 1. The compounds were tested for binding affinity and functional activity at 5-HT1AR and α1-adrenoceptor subtypes and SAR studies were drawn. In particular, compounds 9, 27 and 30 emerged as promising α1 receptor antagonists, while compound 10 behaves as the most potent and efficacious 5-HT1AR agonist. All the compounds were docked into the 5HT1AR theoretical model and the results were in agreement with the biological experimental data. These findings may represent a new starting point for developing more selective α1 or 5-HT1AR ligands.

(2,2‐Diphenyl‐[1,3]oxathiolan‐5‐ylmethyl)‐(3‐phenyl‐propyl)‐amine: a Potent and Selective 5‐HT1A Receptor Agonist

A selective 5‐HT1A receptor agonist: A new series of ligands acting at 5‐HT1A serotonin receptor were identified. Among them (2,2‐diphenyl‐[1,3]oxathiolan‐5‐yl‐methyl)‐(3‐phenyl‐propyl)amine (shown) possesses outstanding activity (pKi=8.72, pD2=7.67, Emax=85) and selectivity (5‐HT1A/α1D>150), and represents a new 5‐HT1A agonist chemotype.

Synthesis of 6-O-methotrexylhyaluronan as a drug delivery system

Selective halogenation of hyaluronan and partial halogen substitution by methotrexate led to 6-chloro-6-deoxy-6-O-methotrexylhyaluronan, a potential antitumor drug. The remaining halogen could be further substituted by a second organic carboxylate, leading to mixed esters. 6-O-Acetyl-6-O-methotrexylhyaluronan and 6-O-butyryl-6-O-methotrexylhyaluronan were thus synthesized and characterized by NMR spectroscopy.

Exhaustive CoMFA and CoMSIA analyses around different chemical entities: a ligand-based study exploring the affinity and selectivity profiles of 5-HT1A ligands

Abstract The 5-hydroxytryptamine (5-HT1A) receptors represent an attractive target in drug discovery. In particular, 5-HT1A agonists and partial agonists are deeply investigated for their potential role in the treatment of anxiety, depression, ischaemic brain disorder and more recently, of pain. On the other hand, 5-HT1A antagonists have been revealed promising compounds in cognition disorders and, lately, in cancer. Thus, the discovery of 5HT1A ligands is nowadays an appealing research activity in medicinal chemistry. In this work, Comparative Molecular Fields Analysis (CoMFA) and Comparative Molecular Similarity Index Analysis (CoMSIA) were applied on an in-house library of 5-HT1A ligands bearing different chemical scaffolds in order to elucidate their affinity and selectivity for the target. Following this procedure, a number of structural modifications have been drawn for the development of much more effective 5-HT1AR ligands.

Synthesis and Structure–Activity Relationships of Triazaspirodecanone Derivatives as Nociceptin/Orphanin FQ Receptor Ligands

Several spiroxatrine derivatives were synthesized and evaluated as potential NOP receptor ligands. Structural modifications of the 1,4‐benzodioxane moiety of spiroxatrine have been the focus of this research project. The structure–activity relationships that emerged indicate that the presence of an H‐bond donor group (hydroxyl group) is more favorable for NOP activity when it is positioned α with respect to the CH2 linked to the 1‐phenyl‐1,3,8‐triaza‐spiro[4.5]decan‐4‐one portion. Moreover, cis diastereoisomers of the hydroxyl derivatives4 and 22 show a moderately higher degree of stereoselectivity than trans isomers. In particular, the spiropiperidine derivative cis‐4 has submicromolar agonistic activity, and it will be the reference compound for the design and synthesis of new NOP agonists.