3D-Printing of Capsule Devices as Compartmentalization Tools for Supported Reagents in the Search of Antiproliferative Isatins.

The application of high throughput synthesis methodologies in the generation of active pharmaceutical ingredients (APIs) currently requires the use of automated and easily scalable systems, easy dispensing of supported reagents in solution phase organic synthesis (SPOS), and elimination of purification and extraction steps. The recyclability and recoverability of supported reagents and/or catalysts in a rapid and individualized manner is a challenge in the pharmaceutical industry. This objective can be achieved through a suitable compartmentalization of these pulverulent reagents in suitable devices for it. This work deals with the use of customized polypropylene permeable-capsule devices manufactured by 3D printing, using the fused deposition modeling (FDM) technique, adaptable to any type of flask or reactor. The capsules fabricated in this work were easily loaded "in one step" with polymeric reagents for use as scavengers of isocyanides in the work-up process of Ugi multicomponent reactions or as compartmentalized and reusable catalysts in copper-catalyzed cycloadditions (CuAAC) or Heck palladium catalyzed cross-coupling reactions (PCCCRs). The reaction products are different series of diversely substituted isatins, which were tested in cancerous cervical HeLa and murine 3T3 Balb fibroblast cells, obtaining potent antiproliferative activity. This work demonstrates the applicability of 3D printing in chemical processes to obtain anticancer APIs.

Enantiospecific Recognition at the A2B Adenosine Receptor by Alkyl 2-Cyanoimino-4-substituted-6-methyl-1,2,3,4-tetrahydropyrimidine-5-carboxylates.

A novel family of structurally simple, potent, and selective nonxanthine A2BAR ligands was identified, and its antagonistic behavior confirmed through functional experiments. The reported alkyl 2-cyanoimino-4-substituted-6-methyl-1,2,3,4-tetrahy-dropyrimidine-5-carboxylates (16) were designed by bioisosteric replacement of the carbonyl group at position 2 in a series of 3,4-dihydropyrimidin-2-ones. The scaffold (16) documented herein contains a chiral center at the heterocycle. Accordingly, the most attractive ligand of the series [(±)16b, Ki = 24.3 nM] was resolved into its two enantiomers by chiral HPLC, and the absolute configuration was established by circular dichroism. The biological evaluation of both enantiomers demonstrated enantiospecific recognition at A2BAR, with the (S)-16b enantiomer retaining all the affinity (Ki = 15.1 nM), as predicted earlier by molecular modeling. This constitutes the first example of enantiospecific recognition at the A2B adenosine receptor and opens new possibilities in ligand design for this receptor.

Integrated Ugi-based assembly of functionally, skeletally, and stereochemically diverse 1,4-benzodiazepin-2-ones.

A practical, integrated and versatile U-4CR-based assembly of 1,4-benzodiazepin-2-ones exhibiting functionally, skeletally, and stereochemically diverse substitution patterns is described. By virtue of its convergence, atom economy, and bond-forming efficiency, the methodology documented herein exemplifies the reconciliation of structural complexity and experimental simplicity in the context of medicinal chemistry projects.

Synthesis and biological evaluation of a series of aminoalkyl-tetralones and tetralols as dual dopamine/serotonin ligands.

A series of novel α-tetralone and α-tetralol derivatives was synthesized, and their binding affinities for 5-HT(2A) and D2 receptors, the most important targets implicated in the anti-schizophrenia drug action, were evaluated to elucidate how substitutions in the aromatic ring of the pharmacophore affect to the affinity or selectivity for these receptors. The replacement of the H-7 in the tetrahydronaphthalene system by an amino group resulted in privileged 5-HT(2A) affinity of the 6-fluorobenzo[d]isoxazol derivative 36 and the alcohol 25 both showing a pK(i) value for 5-HT(2A) higher than 8.3 and good binding affinities for D2 receptor leading to a Meltzer's ratio characteristic of an atypical antipsychotic profile. Additionally, a small collection of 3-aminomethyltetralone derivatives was prepared and examined here for their affinities and selectivities as 5-HT(2A)/D2 dual ligands. Compound 11 shows the best profile with good pKi values for 5-HT(2A) and D2 receptors leading to a Meltzer's ratio characteristic of a typical antipsychotic behaviour. These three compounds behaved as competitive antagonists of both 5-HT(2A) and D2 receptors, and might be promising pharmacological tools for the investigation of the dual function of the 5HT(2A)-D2 ligands.

Synthesis and binding affinity of new 1,4-disubstituted triazoles as potential dopamine D(3) receptor ligands.

A series of new 1,4-disubstituted triazoles was prepared from appropriate arylacetylenes and aminoalkylazides using click chemistry methodology. These compounds were evaluated as potential ligands on several subtypes of dopamine receptors in in vitro competition assays, showing high affinity for dopamine D3 receptors, lower affinity for D2 and D4, and no affinity for the D1 receptors. Compound 18 displayed the highest affinity at the D3 receptor with a Ki value of 2.7 nM, selectivity over D2 (70-fold) and D4 (200-fold), and behaviour as a competitive antagonist in the low nanomolar range.

Aromatic ring functionalization of benzolactam derivatives: new potent dopamine D3 receptor ligands.

Since the discovery of the dopamine D(3) receptor, an intensive effort has been directed toward the development of potent and selective ligands in order to elucidate the function and potential therapeutic advantages of targeting D(3) receptors. As a part of our efforts, a novel series of substituted benzolactams derivatives was synthesized mostly through palladium-catalyzed reactions. Their affinities on D(1)-D(4) receptors were evaluated and the data led us to highly potent D(3) ligands, some of them highly selective for D(3) receptor, compared to the related dopamine receptor subtypes. Functional D(3) activity assays of the most relevant compounds have been carried out revealing antagonist as well as partial agonist activity.

Synthesis, 3D-QSAR, and structural modeling of benzolactam derivatives with binding affinity for the D(2) and D(3) receptors.

A series of 37 benzolactam derivatives were synthesized, and their respective affinities for the dopamine D(2) and D(3) receptors evaluated. The relationships between structures and binding affinities were investigated using both ligand-based (3D-QSAR) and receptor-based methods. The results revealed the importance of diverse structural features in explaining the differences in the observed affinities, such as the location of the benzolactam carbonyl oxygen, or the overall length of the compounds. The optimal values for such ligand properties are slightly different for the D(2) and D(3) receptors, even though the binding sites present a very high degree of homology. We explain these differences by the presence of a hydrogen bond network in the D(2) receptor which is absent in the D(3) receptor and limits the dimensions of the binding pocket, causing residues in helix 7 to become less accessible. The implications of these results for the design of more potent and selective benzolactam derivatives are presented and discussed.

Synthesis and binding affinity of potential atypical antipsychotics with the tetrahydroquinazolinone motif.

A series of 8 new tetrahydroquinazolinone derivatives was synthesized and evaluated for binding affinity to D2 and 5-HT2A human receptors; in addition, some properties related to blood-brain barrier penetration were calculated. From the results of these assays, three compounds were selected for further binding tests on D1, D3, and 5-HT2C human receptors, which are thought to be involved in schizophrenia. From these data, compound 19b emerged as the most promising candidate based on its good binding affinities for D1, D2, and D3 receptors, high affinity for 5-HT2A, low affinity for 5-HT2C receptors, and a Meltzer's ratio characteristic of an atypical antipsychotic profile.

Synthesis, binding affinity and SAR of new benzolactam derivatives as dopamine D3 receptor ligands.

A series of new benzolactam derivatives was synthesized and the derivatives were evaluated for their affinities at the dopamine D(1), D(2), and D(3) receptors. Some of these compounds showed high D(2) and/or D(3) affinity and selectivity over the D(1) receptor. The SAR study of these compounds revealed structural characteristics that decisively influenced their D(2) and D(3) affinities. Structural models of the complexes between some of the most representative compounds of this series and the D(2) and D(3) receptors were obtained with the aim of rationalizing the observed experimental results. Moreover, selected compounds showed moderate binding affinity on 5-HT(2A) which could contribute to reducing the occurrence of extrapyramidal side effects as potential antipsychotics.

Synthesis, binding affinity, and molecular docking analysis of new benzofuranone derivatives as potential antipsychotics.

The complex etiology of schizophrenia has prompted researchers to develop clozapine-related multitarget strategies to combat its symptoms. Here we describe a series of new 6-aminomethylbenzofuranones in an effort to find new chemical structures with balanced affinities for 5-HT2 and dopamine receptors. Through biological and computational studies of 5-HT2A and D2 receptors, we identified the receptor serine residues S3.36 and S5.46 as the molecular keys to explaining the differences in affinity and selectivity between these new compounds for this group of receptors. Specifically, the ability of these compounds to establish one or two H-bonds with these key residues appears to explain their difference in affinity. In addition, we describe compound 2 (QF1004B) as a tool to elucidate the role of 5-HT2C receptors in mediating antipsychotic effects and metabolic adverse events. The compound 16a (QF1018B) showed moderate to high affinities for D2 and 5-HT2A receptors, and a 5-HT2A/D2 ratio was predictive of an atypical antipsychotic profile.

Synthesis and binding affinity of new pyrazole and isoxazole derivatives as potential atypical antipsychotics.

We describe the synthesis and binding affinities on D(2), 5-HT(2A) and 5-HT(2C) receptors of 6-aminomethyl-6,7-dihydro-1H-indazol-4(5H)-ones and 6-aminomethyl-6,7-dihydro-3-methyl-benzo[d]isoxazol-4(5H)-ones, as conformationally constrained butyrophenone analogues. One of the new compounds showed good in vitro binding features, and a Meltzer's ratio characteristic of an atypical antipsychotic profile.

Multistructure 3D-QSAR studies on a series of conformationally constrained butyrophenones docked into a new homology model of the 5-HT2A receptor.

The present study is part of a long-term research project aiming to gain insight into the mechanism of action of atypical antipsychotics. Here we describe a 3D-QSAR study carried out on a series of butyrophenones with affinity for the serotonin-2A receptor, aligned by docking into the binding site of a receptor model. The series studied has two peculiarities: (i) all the compounds have a chiral center and can be represented by two enantiomeric structures, and (ii) many of the structures can bind the receptor in two alternative orientations, posing the problem of how to select a single representative structure for every compound. We have used an original solution consisting of the simultaneous use of multiple structures, representing different configurations, binding conformations, and positions. The final model showed good statistical quality (n = 426, r2 = 0.84, q2LOO = 0.81) and its interpretation provided useful information, not obtainable from the simple inspection of the ligand-receptor complexes.

Synthesis and biological evaluation of new quinazoline and cinnoline derivatives as potential atypical antipsychotics.

Four new diaza analogues (14, 15, 23, and 24) of the conformationally constrained aminobutyrophenone derivatives QF0104B (5) and QF0108B (6) were synthesized (Schemes 2 and 3), and evaluated for their binding affinities (Table) towards the serotonin 5-HT2A and 5-HT2C, and the dopamine D2 receptors. Among the new compounds, the quinazoline derivative 15 (= 7-{[4-(4-fluorobenzoyl)piperidin-1-yl]methyl}-5,6,7,8-tetrahydroquinazolin-5-one) exhibited the highest affinities towards the serotonin 5-HT2A and dopamine D2 receptors, and it is in the borderline of potential atypical antipsychotics. The cinnoline derivative 23 (= 7-{[4-(4-fluorobenzoyl)piperidin-1-yl]methyl}-5,6,7,8-tetrahydro-3-methylcinnolin-5-one) displayed high selectivity in its binding profile towards the 5-HT2C compared to both the 5-HT2A and D2 receptors.

QF2004B, a potential antipsychotic butyrophenone derivative with similar pharmacological properties to clozapine.

The aim of the present work was to characterize a lead compound displaying relevant multi-target interactions, and with an in vivo behavioral profile predictive of atypical antipsychotic activity. Synthesis, molecular modeling and in vitro and in vivo pharmacological studies were carried out for 2-[4-(6-fluorobenzisoxazol-3-yl)piperidinyl]methyl-1,2,3,4-tetrahydro-carbazol-4-one (QF2004B), a conformationally constrained butyrophenone analogue. This compound showed a multi-receptor profile with affinities similar to those of clozapine for serotonin (5-HT2A, 5-HT1A, and 5-HT2C), dopamine (D1, D2, D3 and D4), alpha-adrenergic (alpha1, alpha2), muscarinic (M1, M2) and histamine H1 receptors. In addition, QF2004B mirrored the antipsychotic activity and atypical profile of clozapine in a broad battery of in vivo tests including locomotor activity (ED50 = 1.19 mg/kg), apomorphine-induced stereotypies (ED50 = 0.75 mg/kg), catalepsy (ED50 = 2.13 mg/kg), apomorphine- and DOI (2,5-dimethoxy-4-iodoamphetamine)-induced prepulse inhibition (PPI) tests. These results point to QF2004B as a new lead compound with a relevant multi-receptor interaction profile for the discovery and development of new antipsychotics.

Synthesis and binding affinity of novel 3-aminoethyl-1-tetralones, potential atypical antipsychotics.

A series of 3-aminoethyl-1-tetralones, conformationally constrained higher homologues of haloperidol (standard for typical antipsychotic profile), have been obtained by a four-step route from valerolactone. Their binding affinities at dopamine D(2) and serotonin 5-HT2A and 5-HT2C receptors were determined, showing in some cases an atypical antipsychotic profile.

Chemoenzymatic synthesis and binding affinity of novel (R)- and (S)-3-aminomethyl-1-tetralones, potential atypical antipsychotics.

A series of (R)- and (S)-3-aminomethyl-1-tetralones, conformationally constrained analogues of haloperidol, have been obtained by enzymatic resolution of the corresponding racemic 3-hydroxymethyl-1-tetralones using Pseudomonas fluorescens lipase. Their binding affinities at dopamine D(2) and serotonin 5-HT(2A) and 5-HT(2C) receptors were determined showing in some cases an atypical antipsychotic profile with Meltzer's ratio higher than 1.30.

Conformationally constrained butyrophenones as new pharmacological tools to study 5-HT 2A and 5-HT 2C receptor behaviours.

This study presents new pharmacological and molecular modelling studies on a recently described series of conformationally constrained butyrophenones. Alignment-free three-dimensional quantitative structure-activity relationship models developed on the basis of GRid Independent descriptors and partial least squares regression analysis, allow feasible predictions of activity of new compounds and reveal structural requirements for optimal affinity, particularly in the case of the 5-HT(2A) receptor. The requirements for the 5-HT(2A) affinity consist in a precise distance between hydrogen bond donor (protonated amino group) and hydrogen bond acceptor groups, as well as an optimal distance between the protonated amino group and the farthest extreme of the compounds. Another significant result has been the characterisation of two structurally similar compounds as interesting pharmacological tools (1-[(4-Oxo-4,5,6,7-tetrahydrobenzo[b]furan-5-yl)ethyl]-4-(6-fluorobenzisoxazol-3-yl)piperidine and 1-[(4-Oxo-4,5,6,7-tetrahydrobenzo[b]furan-6-yl)methyl]-4-(6-fluorobenzisoxazol-3-yl)piperidine). In spite of their structural similarity, the first compound shows clearly higher affinity for the 5-HT(2C) receptor (about 100 fold) and higher Meltzer ratio (1.17 vs. 0.99) than the second. Moreover, the first compound inhibits arachidonic acid release in a biphasic concentration-dependent way in functional experiments at the 5-HT(2A) receptor and it acts as inverse agonist at the 5-HT(2C) receptor, behaviours that are not shown by the second compound.

New serotonin 5-HT(2A), 5-HT(2B), and 5-HT(2C) receptor antagonists: synthesis, pharmacology, 3D-QSAR, and molecular modeling of (aminoalkyl)benzo and heterocycloalkanones.

A series of 52 conformationally constrained butyrophenones have been synthesized and pharmacologically tested as antagonists at 5-HT(2A), 5-HT(2B), and 5-HT(2C) serotonin receptors, useful for dissecting the role of each 5-HT(2) subtype in pathophysiology. These compounds were also a consistent set for the identification of structural features relevant to receptor recognition and subtype discrimination. Six compounds were found highly active (pK(i) > 8.76) and selective at the 5-HT(2A) receptor vs 5-HT(2B) and/or 5-HT(2C) receptors. Piperidine fragments confer high affinity at the 5-HT(2A) receptor subtype, with benzofuranone- and thiotetralonepiperidine as the most selective derivatives over 5-HT(2C) and 5-HT(2B) receptors, respectively; K(i) (2A/2C) and/or K(B) (2A/2B) ratios greater than 100 were obtained. Compounds showing a more pronounced selectivity at 5-HT(2A)/5-HT(2C) than at 5-HT(2A)/5-HT(2B) bear 6-fluorobenzisoxazolyl- and p-fluorobenzoylpiperidine moieties containing one methylene bridging the basic piperidine to the alkanone moiety. An ethylene bridge between the alkanone and the amino moieties led to ligands with higher affinities for the 5-HT(2B) receptor. Significant selectivity at the 5-HT(2B) receptor vs 5-HT(2C) was observed with 1-1[(1-oxo-1,2,3,4-tetrahydro-3-naphthyl)methyl]-4-[3-(p-fluorobenzoyl)propyl]piperazine (more than 100-fold higher). Although piperidine fragments also confer higher affinity at 5-HT(2C) receptors, only piperazine-containing ligands were selective over 5-HT(2A). Moderate selectivity was observed at 5-HT(2C) vs 5-HT(2B) (10-fold) with some compounds bearing a 4-[3-(6-fluorobenzisoxazolyl)]piperidine moiety in its structure. Molecular determinants for antagonists acting at 5-HT(2A) receptors were identified by 3D-QSAR (GRID-GOLPE) studies. Docking simulations at 5-HT(2A) and 5-HT(2C) receptors suggest a binding site for the studied type of antagonists (between transmembrane helices 2, 3, and 7) different to that of the natural agonist serotonin (between 3, 5, and 6).