Synthesis and SAR of adatanserin: novel adamantyl aryl- and heteroarylpiperazines with dual serotonin 5-HT(1A) and 5-HT(2) activity as potential anxiolytic and antidepressant agents

Advances in drug design and therapeutic potential of selective or multitarget 5-HT1A receptor ligands

5-HT1A receptor (5-HT1A-R) is a serotoninergic G-protein coupled receptor subtype which contributes to several physiological processes in both central nervous system and periphery. Despite being the first 5-HT-R identified, cloned and studied, it still represents a very attractive target in drug discovery and continues to be the focus of a myriad of drug discovery campaigns due to its involvement in numerous neuropsychiatric disorders. The structure-activity relationship studies (SAR) performed over the last years have been devoted to three main goals: (i) design and synthesis of 5-HT1A-R selective/preferential ligands; (ii) identification of 5-HT1A-R biased agonists, differentiating pre- versus post-synaptic agonism and signaling cellular mechanisms; (iii) development of multitarget compounds endowed with well-defined poly-pharmacological profiles targeting 5-HT1A-R along with other serotonin receptors, serotonin transporter (SERT), D2-like receptors and/or enzymes, such as acetylcholinesterase and phosphodiesterase, as a promising strategy for the management of complex psychiatric and neurodegenerative disorders. In this review, medicinal chemistry aspects of ligands acting as selective/preferential or multitarget 5-HT1A-R agonists and antagonists belonging to different chemotypes and developed in the last 7 years (2017-2023) have been discussed. The development of chemical and pharmacological 5-HT1A-R tools for molecular imaging have also been described. Finally, the pharmacological interest of 5-HT1A-R and the therapeutic potential of ligands targeting this receptor have been considered.

Transaminase Catalysis for Enantiopure Saturated Heterocycles as Potential Drug Scaffolds

As efforts in rational drug design are driving the pharmaceutical industry towards more complex molecules, the synthesis and production of these new drugs can benefit from new reaction routes. In addition to the introduction of new centers of asymmetry, complexity can be also increased by ring saturation, which also provides improved developability measures. Therefore, in this report, our aim was to develop transaminase (TA)-catalyzed asymmetric synthesis of a new group of potential chiral drug scaffolds comprising a saturated amine heterocycle backbone and an asymmetric primary amine sidechain (55a–g). We screened the Codex® Amine Transaminase Kit of 24 transaminases with the morpholine containing ketone 57a, resulting in one (R)-selective TA and three (S)-selective TAs operating at 100 mM substrate concentration and 25 v/v% isopropylamine (IPA) content. The optimized reaction conditions were than applied for asymmetric transamination of further six ketones (57b–g) containing various amine heterocycles, in which a strong effect of the substitution pattern of the γ-position relative to the substituted N-atom could be observed. Mediated by the most enantiotope selective (S)-TAs in scaled-up process, the (S)-amines [(S)-55a–g] were isolated with moderate-to-excellent yields (47–94%) in enantiopure form (>99% ee).

Synthesis and crystal structure of 3-(adamantan-1-yl)-4-(2-bromo-4-fluoro-phen-yl)-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C18H19BrFN3S, the 1,2,4-triazole ring is nearly planar with a maximum deviation of -0.009 (3) and 0.009 (4) Å, respectively, for the S-bound C atom and the N atom bonded to the bromo-fluoro-phenyl ring. The phenyl and triazole rings are almost perpendicular to each other, forming a dihedral angle of 89.5 (2)°. In the crystal, the mol-ecules are linked by weak C-H⋯π(phen-yl) inter-actions, forming supra-molecular chains extending along the c-axis direction. The crystal packing is further consolidated by inter-molecular N-H⋯S hydrogen bonds and by weak C-H⋯S inter-actions, yielding double chains propagating along the a-axis direction. The crystal studied was refined as a racemic twin.

Crystal structure of 3,5-bis(trifluoromethyl)benzyl(Z)-N-(adamantan-1-yl)morpholine-4-carbothioimidate, C24H28F6N2OS

C24H28F6N2OS, monoclinic, P21/n (no. 14), a = 17.4112(7) Å, b = 8.3694(3) Å, c = 17.6728(7) Å, β = 104.612(2)°, V = 2492.01(17) Å3, Z = 4, R gt(F) = 0.0603, wR(F 2) = 0.1704, T = 293(2) K.

Crystal structure of benzoato-κO-bis(1,3,5-triaza-7-phosphaadamantane-κP)silver(I) monohydrate C19H31AgN6O3P2

C19H31AgN6O3P2, monoclinic, P21/c (no. 14), a = 16.5661(8) Å, b = 6.1644(3) Å, c = 23.8822(10) Å, β = 114.553(3)°, V = 2218.32(18) Å3, Z = 4, R gt(F) = 0.0188, wR ref(F 2) = 0.0525, T = 100(2) K.

Crystal structure of (Z)-3-(adamantan-1-yl)-1-(3-chlorophenyl)-S-benzylisothiourea, C24H27ClN2S

C24H27ClN2S, triclinicP1̅ (no. 2),a= 7.1670(3) Å,b= 12.2734(6) Å,c= 13.1560(6) Å,α= 109.605(2)°,β= 96.515(2)°,γ= 97.312(2)°,V= 1066.08(8) Å3,Z= 2,Rgt(F)= 0.0515,wRref(F2) = 0.1396,T= 296(2) K.

Crystal structure of 4-bromobenzyl (Z)-N′-(adamantan-1-yl)-4-phenylpiperazine-1-carbothioimidate, C28H34BrN3S

C28H34BrN3S, monoclinic, P21/c (no. 14), a = 10.4529(8) Å, b = 11.8724(10) Å, c = 21.3800(19) Å, β = 101.864(3)°, V = 2596.6(4) Å3, Z = 4, R gt(F) = 0.060, wR ref(F 2) = 0.148, T = 296(2).

Crystal structure of 3-(adamantan-1-yl)-1-(4-bromophenyl)urea, C17H21BrN2O

C17H21BrN2O, orthorhombic, Pna21 (no. 33), a = 9.2558(12) Å, b = 13.0186(17) Å, c = 13.4684(18) Å, V = 1622.9(4) Å3, Z = 4, R gt(F) = 0.0471, wR ref(F 2) = 0.1059, T = 100 K.

Crystal structure of 1-(adamantan-1-yl)-3-(3-chlorophenyl)thiourea, C17H21ClN2S

C17H21ClN2S, orthorhombic,Pca21(no. 29),a= 25.4796(11) Å,b= 6.7503(3) Å,c= 18.9971(9) Å,V= 3267.4(3) Å3,Z= 8,Rgt(F) = 0.045,wRref(F2) = 0.106,T= 293(2).

Crystal structure of 1-(adamantan-1-yl)-3-(4-bromophenyl)thiourea, C17H21BrN2S

C17H21BrN2S, orthorhombic,Pbca(No. 61),a= 17.0675(7) Å,b= 8.3422(3) Å,c= 22.5970(8) Å,V= 3217.4(2) Å3,Z= 8,Rgt(F)= 0.0329,wRref(F2) = 0.0724,T= 100 K.

Crystal structure of N-(adamantan-1-yl)-4-phenylpiperazine-1-carbothioamide, C21H29N3S

C21H29N3S, orthorhombic, Pbca (No. 61), a = 9.8658(7) Å, b = 11.7298(9) Å, c = 31.960(2) Å, V = 3698.5(5) Å3, Z = 8, R gt (F) = 0.0644, wR ref (F 2) = 0.1684, T = 100 K.

Crystal structure of 3-(adamantan-1-yl)-1-[(4-benzylpiperazin-1-yl)methyl]-4-[(E)-(2,6-difluorobenzylidene)amino]-1H-1,2,4-triazole-5(4H)-thione, C31H36F2N6S

C31H36F2N6S, monoclinic, P21/c (no. 14), a = 14.7561(8) Å, b = 24.6766(13) Å, c = 7.7811(4) Å, β = 95.888(2)°, V = 2818.4(3) Å3, Z = 4, R gt (F) = 0.0624, wR ref (F 2 ) = 0.1445, T = 100 K.

Crystal structure of 1-(adamantan-1-yl)-3-phenylthiourea, C17H22N2S

C17H22N2S, orthorhombic, Pbca (no. 61), a = 12.0579(7) Å, b = 11.12133(5) Å, c = 21.9741(13) Å, V = 2946.7(3) Å3, Z = 8, Rgt(F) = 0.0470, wRref(F2) = 0.1125, T = 100 K.

Crystal structure of 1-(adamantan-1-yl)-3-(4-chlorophenyl)thiourea, C17H21ClN2S

C17H21ClN2S, orthorhombic,Pbca(no. 61),a= 17.2134(6) Å,b= 8.2251(2) Å,c= 22.5220(7) Å,V= 3188.71(17) Å3,Z= 8,Rgt(F)= 0.0371,wRref(F2)= 0.0933,T= 100 K.

FT-IR and FT-Raman spectroscopic signatures, vibrational assignments, NBO, NLO analysis and molecular docking study of 2-{[5-(adamantan-1-yl)-4-methyl-4H-1,2,4-triazol-3-yl]sulfanyl}-N,N-dimethylethanamine

FT-Raman and FT-IR spectra of the title compound 2-{[5-(adamantan-1-yl)-4-methyl-4H-1,2,4-triazol-3-yl]sulfanyl}-N,N-dimethylethanamine were recorded and investigated. The DFT/B3LYP/6-311++G(d,p) method was used to compute the vibrational wavenumbers. A good coherence between experimental and theoretical wavenumbers shows the preciseness of the assignments. NLO properties like the dipole moment, polarizability, first static hyperpolarizability, molecular electrostatic potential surface and contour map have been calculated to get a better cognizance of the properties of the title molecule. Natural bond orbital analysis has been applied to estimate the stability of the molecule arising from charge delocalization. The molecular docking studies concede that title compound may exhibit HIV-1 Protease 1N49 inhibitory activity.

Antimicrobial and hypoglycemic activities of novel N-Mannich bases derived from 5-(1-adamantyl)-4-substituted-1,2,4-triazoline-3-thiones

The reaction of 5-(1-adamantyl)-4-ethyl or allyl-1,2,4-triazoline-3-thione with formaldehyde solution and various 1-substituted piperazines yielded the corresponding N-Mannich bases. The newly synthesized N-Mannich bases were tested for in vitro inhibitory activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Six compounds showed potent antibacterial activity against one or more of the tested microorganisms, while two compounds exhibited moderate activity against the tested Gram-positive bacteria. None of the newly synthesized compounds were proved to possess marked activity against Candida albicans. The oral hypoglycemic activity of six compounds was determined in streptozotocin (STZ)-induced diabetic rats. Four compounds produced significant strong dose-dependent reduction of serum glucose levels, compared to gliclazide at 10 mg/kg dose level (potency ratio > 75%).

Vibrational spectroscopic studies (FT-IR, FT-Raman) and quantum chemical calculations on 5-(Adamantan-1-yl)-3-[(4-fluoroanilino)methyl]-2,3-dihydro-1,3,4-oxadiazole-2-thione, a potential chemotherapeutic agent

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 5-(Adamantan-1-yl)-3-[(4-fluoroanilino)methyl]-2,3-dihydro-1,3,4-oxadiazole-2-thione are investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes vibrations was done using GAR2PED program. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated geometrical parameters are in agreement with the XRD data. The calculated first hyperpolarizability is high and the title compound is an attractive candidate for further studies in non-linear optical applications. To estimate the chemical reactivity of the molecule, the molecular electrostatic potential is calculated for the optimized geometry of the molecule.

Synthesis, antimicrobial, and anti-inflammatory activity, of novel S-substituted and N-substituted 5-(1-adamantyl)-1,2,4-triazole-3-thiols

The reaction of 5-(1-adamantyl)-4-phenyl-1,2,4-triazoline-3-thione (compound 5) with formaldehyde and 1-substituted piperazines yielded the corresponding N-Mannich bases 6a-f. The reaction of 5-(1-adamantyl)-4-methyl-1,2,4-triazoline-3-thione 8 with various 2-aminoethyl chloride yielded separable mixtures of the S-(2-aminoethyl) 9a-d and the N-(2-aminoethyl) 10a-d derivatives. The reaction of compound 5 with 1-bromo-2-methoxyethane, various aryl methyl halides, and ethyl bromoacetate solely yielded the S-substituted products 11, 12a-d, and 13. The new compounds were tested for activity against a panel of Gram-positive and Gram-negative bacteria and the pathogenic fungus Candida albicans. Compounds 6b, 6c, 6d, 6e, 6f, 10b, 10c, 10d, 12c, 12d, 12e, 13, and 14 displayed potent antibacterial activity. Meanwhile, compounds 13 and 14 produced good dose-dependent anti-inflammatory activity against carrageenan-induced paw edema in rats.

Synthesis and antimicrobial activity of novel 5-(1-adamantyl)-2-aminomethyl-4-substituted-1,2,4-triazoline-3-thiones

The reaction of 5-(1-adamantyl)-4-substituted-1,2,4-triazoline-3-thione 5a,b and 10a,b with formaldehyde solution and various primary aromatic amines or 1-substituted piperazines yielded the corresponding N-Mannich bases 6a-o, 7a-g and 11a-i. The newly synthesized N-Mannich bases 6a-o, 7a-g and 11a-i were tested for in vitro inhibitory activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. The compounds 6j, 6l, 6m, 7a, 7b, 7c, 7d, 7f, 11a, 11b, 11c, 11d, 11e, 11f, 11h and 11i displayed moderate to good activity against the tested Gram-positive bacteria, while compounds 7c, 11c, 11d, 11f and 11h showed potent broad spectrum antibacterial activity. None of the newly synthesized compounds were proved to possess marked activity against C. albicans.

Synthesis and antimicrobial activity of N'-heteroarylidene-1-adamantylcarbohydrazides and (±)-2-(1-adamantyl)-4-acetyl-5-[5-(4-substituted phenyl-3-isoxazolyl)]-1,3,4-oxadiazolines

The reaction of adamantane-1-carbohydrazide (1) with heterocyclic aldehydes, namely 5-(4-chlorophenyl)isoxazole-3-carboxaldehyde (2a), 5-(4-methylphenyl)isoxazole-3-carboxaldehyde (2b), 5-(4-methoxyphenyl)isoxazole-3-carboxaldehyde (2c), 1H-imidazole-2-carboxaldehyde and 2-butyl-4-chloro-1H-imidazole-5-carboxaldehyde, in ethanol, yielded the corresponding N'-heteroarylidene-1-adamantylcarbohydrazides 3a, 3b, 3c, 4 and 5, respectively, in good yields. The 4-acetyl-1,3,4-oxadiazoline analogues 6a‑c were prepared in 48-55% yields by heating their corresponding N'-heteroarylidene-1-adamantylcarbohydrazides 3a-c with acetic anhydride for two hours. Compounds 3a-c, 4, 5 and 6a-c were tested for in vitro activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compounds 4 and 5 displayed potent broad-spectrum antimicrobial activity, while compounds 3a-c showed good activity against the Gram-positive bacteria.

Antidepressant potential of nitrogen-containing heterocyclic moieties: An updated review

Depression is currently the fourth leading cause of disease or disability worldwide. Antidepressant is approved for the treatment of major depression (including paediatric depression), obsessive-compulsive disorder (in both adult and paediatric populations), bulimia nervosa, panic disorder and premenstrual dysphoric disorder. Antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. Many drugs produce an antidepressant effect, but restrictions on their use have caused controversy and off-label prescription a risk, despite claims of superior efficacy. Our current understanding of its pathogenesis is limited and existing treatments are inadequate, providing relief to only a subset of people suffering from depression. Reviews of literature suggest that heterocyclic moieties and their derivatives has proven success in treating depression.

Synthesis, antimicrobial, and anti-inflammatory activities of novel 5-(1-adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazoles and related derivatives

The reaction of 5-(1-adamantyl)-4-amino-3-mercapto-1,2,4-triazole (5) with various aromatic aldehydes in ethanol or acetic acid yielded the corresponding 4-arylideneamino derivatives 6a–v. Treatment of the 4-(2,6-difluoro- and dichlorobenzylideneamino) derivatives 6o and 6q with 1-substituted piperazines, and formaldehyde solution in ethanol afforded good yields of the corresponding 5-(1-adamantyl)-4-(2,6-dihalobenzylideneamino-2-(4-substituted-1-piperazinylmethyl)-1,2,4-triazoline-3-thiones 7a–p. 5-(1-Adamantyl)-4-arylideneamino-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thiones 8a–n, were similarly prepared via the reaction of the corresponding arylideneamino derivative with ethyl 4-piperidinecarboxylate and formaldehyde solution in ethanol. Compounds 6a–v, 7a–p and 8a–n were tested for in vitro activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Several derivatives showed good or moderate activities, particularly against the tested Gram-positive bacteria. In addition, the in vivo anti-inflammatory activity of 21 compounds was determined using the carrageenan-induced paw oedema method in rats. Compounds 7d, 7g, 7i, 7j, 7l, 8c, 8e and 8l showed good or moderate dose-dependent activity in this area.

Polycyclic compounds: ideal drug scaffolds for the design of multiple mechanism drugs?

Recently there has been a resurging interest in developing multi-functional drugs to treat diseases with complex pathological mechanisms. Such drug molecules simultaneously target multiple etiologies that have been found to be important modulators in specific diseases. This approach has significant promise and may be more effective than using one compound specific for one drug target or, by a polypharmaceutical approach, using a cocktail of two or more drugs. Polycyclic ring structures are useful as starting scaffolds in medicinal chemistry programs to develop multi-functional drugs, and may also be useful moieties added to existing structures to improve the pharmacokinetic properties of drugs currently used in the clinic or under development. This review attempts to provide a synopsis of current published research to exemplify the use of polycyclic compounds as starting molecules to develop multi-functional drugs.