The many faces of the adamantyl group in drug design

Visible-light-initiated manganese-catalyzed Giese addition of unactivated alkyl iodides to electron-poor olefins

Visible-light-initiated Giese addition of unactivated alkyl iodides to electron-poor olefins with catalysis by decacarbonyl dimanganese, Mn₂(CO)₁₀ was reported.

Silyl-mediated photoredox-catalyzed Giese reaction: addition of non-activated alkyl bromides

The emergence of photoredox catalysis has enabled the discovery of mild and efficient conditions for the generation of a variety of radical reaction platforms. Herein is disclosed the development of a conjugate addition reaction of non-activated alkyl bromides to Michael acceptors under visible-light photoredox catalysis. Optimization of the reaction was achieved using high-throughput experimentation (HTE) tools to enable the identification of mild, general and practical reaction conditions. A diverse set of alkyl bromides was successfully added to cyclic or acyclic α,β-unsaturated esters and amides. The features of this transformation allowed also access to a key intermediate of Vorinostat®, an HDAC inhibitor used to fight cancer and HIV.

Crystal structure and Hirshfeld surface analysis of a pyridiniminium bromide salt: 1-[2-(adamantan-1-yl)-2-oxoeth-yl]pyridin-4-iminium bromide

In the cation of the title salt, C17H23N2O+·Br-, the adamantyl moiety and the pyridiniminium ring are inclined to the ketone bridge by torsion angles of -78.1 (2) (C-C-C=O) and 58.3 (2)° (C-C-N-C), respectively, and the ketone bridge has a C-C-C-N torsion angle of 174.80 (15)°. In the crystal, the cations are connected into chains parallel to the c axis by C-H⋯O hydrogen bonds. The chains are further linked into layers parallel to the bc plane by N-H⋯Br and C-H⋯Br hydrogen bonds, C-H⋯π inter-actions and π-π stacking inter-actions [centroid-to-centroid distance = 3.5657 (11) Å]. A Hirshfeld surface analysis, which comprises the dnorm surface, electrostatic potential map and two-dimensional fingerprint plots, was carried out to verify the contribution of the various inter-molecular inter-actions.

Hexacyclo[6.5.1.01,5.05,12.07,11.09,13]tetradecane-4,6,14-trione

The structure of the title cage compound, C14H12O3, encompasses seven fused rings, viz. one four-membered, five five-membered and one six-membered. The four-membered ring is essentially planar, all five-membered rings adopt an envelope conformation and the six-membered ring adopts a boat conformation.

Discovery and Development of 8-Substituted Cycloberberine Derivatives as Novel Antibacterial Agents against MRSA

8-Acetoxycycloberberine (2) with a unique skeleton was first identified to display a potent activity profile against Gram-positive bacteria, especially methicillin-resistant S. aureus (MRSA) with minimum inhibitory concentration (MIC) values of 1-8 μg/mL, suggesting a possible novel mechanism of action against bacteria. Taking 2 as the lead, 23 new 8-substituted cycloberberine (CBBR) derivatives including ether, amine, and amide were synthesized and evaluated for their antibacterial effect. The structure-activity relationship revealed that the introduction of a suitable substituent at the 8-position could greatly enhance the potency against MRSA. Among them, compounds 5d and 9e demonstrated equally effective anti-MRSA potency as lead 2, with an advantage of having a more stable pharmacokinetics feature. A preliminary mechanism study indicated that compound 9e acted upon bacteria partly through catalyzing the cleavage of bacterial DNA. Therefore, we consider that 8-substituted CBBR derivatives constitute a promising class of antibacterial agents in the treatment of MRSA infections.

Synthesis, Characterization, Crystal Structure, and DFT Study of a New Square Planar Cu(II) Complex Containing Bulky Adamantane Ligand

A copper complex with square planar geometry, [(L)CuBr₂] (1), (L = N′-(furan-2-ylmethylene)adamantne-1-carbohydrazide) has been synthesized and characterized by Fourier transfer infrared (FTIR) spectroscopy, elemental analysis, mass spectrometry, and single crystal X-ray diffraction. The crystal of 1 is solved as monoclinic, space group P2₁/m with unit cell parameters: a = 10.8030(8), b = 6.6115(8), c = 12.1264(12) Å, β = 101.124(8)°, V = 849.84(15) ų, Z = 2, and R₁ = 0.0751 with wR₂ = 0.1581 (I > 2 σ). The structure of 1 shows intramolecular hydrogen bonding between the N–H and the furan oxygen which stabilizes the configuration of the complex. Furthermore, inside the lattice there are other weak interactions between bromo ligands and the ligand L. DFT calculations where performed to study the stability of this geometry.

Structural and energetic aspects of adamantane and memantine derivatives of sulfonamide molecular crystals: experimental and theoretical characterisation

A number of new sulfonamide compounds with adamantane and memantine fragments were synthesised and characterised.

15N-Labelling and structure determination of adamantylated azolo-azines in solution

Determining the accurate chemical structures of synthesized compounds is essential for biomedical studies and computer-assisted drug design. The unequivocal determination of N-adamantylation or N-arylation site(s) in nitrogen-rich heterocycles, characterized by a low density of hydrogen atoms, using NMR methods at natural isotopic abundance is difficult. In these compounds, the heterocyclic moiety is covalently attached to the carbon atom of the substituent group that has no bound hydrogen atoms, and the connection between the two moieties of the compound cannot always be established via conventional 1H-1H and 1H-13C NMR correlation experiments (COSY and HMBC, respectively) or nuclear Overhauser effect spectroscopy (NOESY or ROESY). The selective incorporation of 15N-labelled atoms in different positions of the heterocyclic core allowed for the use of 1H-15N (JHN) and 13C-15N (JCN) coupling constants for the structure determinations of N-alkylated nitrogen-containing heterocycles in solution. This method was tested on the N-adamantylated products in a series of azolo-1,2,4-triazines and 1,2,4-triazolo[1,5-a]pyrimidine. The syntheses of adamantylated azolo-azines were based on the interactions of azolo-azines and 1-adamatanol in TFA solution. For azolo-1,2,4-triazinones, the formation of mixtures of N-adamantyl derivatives was observed. The JHN and JCN values were measured using amplitude-modulated 1D 1H spin-echo experiments with the selective inversion of the 15N nuclei and line-shape analysis in the 1D 13С spectra acquired with selective 15N decoupling, respectively. Additional spin-spin interactions were detected in the 15N-HMBC spectra. NMR data and DFT (density functional theory) calculations permitted to suggest a possible mechanism of isomerization for the adamantylated products of the azolo-1,2,4-triazines. The combined analysis of the JHN and JCN couplings in 15N-labelled compounds provides an efficient method for the structure determination of N-alkylated azolo-azines even in the case of isomer formation. The isomerization of adamantylated tetrazolo[1,5-b][1,2,4]triazin-7-ones in acidic conditions occurs through the formation of the adamantyl cation.

In vitro antiproliferative study of novel adamantyl pyridin-4-ones

The preparation of several N-aryl-substituted (phenyl, p-methylphenyl, p-methoxyphenyl, p-nitrophenyl, p-aminophenyl, p-hydroxyphenyl) 3-hydroxy-2-methylpyridin-4-ones as well as their adamantyl derivatives is described, and their in vitro antitumor properties were investigated. The compounds were synthesized in good yields using efficient synthetic routes and methods. Prepared derivatives were evaluated in an antiproliferative in vitro study on 4 cancer cell lines, namely HCT 116 (colon carcinoma), H 460 (lung carcinoma), MCF-7 (breast carcinoma) and K562 (chronic myelogenous leukemia). All tested compounds showed antiproliferative activity ranging from moderate to strong on all inspected cell lines with 4 adamantane containing derivatives being active and selective at low micromolar IC[Formula: see text] concentrations on HCT 116, H 460 and MCF-7. LDH cytotoxicity assay revealed that cytotoxic effects occur after 48 h of exposure. It was shown that there was no change in caspase activity in the treated cells, but there were changes in the cell cycle. All treated samples showed reduced number of cells in the S phase with increased G0/G1 (4b, 5a, 5b) and G2/M (4a) phase.

Privileged Electrophile Sensors: A Resource for Covalent Drug Development

This Perspective delineates how redox signaling affects the activity of specific enzyme isoforms and how this property may be harnessed for rational drug design. Covalent drugs have resurged in recent years and several reports have extolled the general virtues of developing irreversible inhibitors. Indeed, many modern pharmaceuticals contain electrophilic appendages. Several invoke a warhead that hijacks active-site nucleophiles whereas others take advantage of spectator nucleophilic side chains that do not participate in enzymatic chemistry, but are poised to bind/react with electrophiles. The latest data suggest that innate electrophile sensing-which enables rapid reaction with an endogenous signaling electrophile-is a quintessential resource for the development of covalent drugs. For instance, based on recent work documenting isoform-specific electrophile sensing, isozyme non-specific drugs may be converted to isozyme-specific analogs by hijacking privileged first-responder electrophile-sensing cysteines. Because this approach targets functionally relevant cysteines, we can simultaneously harness previously untapped moonlighting roles of enzymes linked to redox sensing.

Crystal structure of 3-(adamantan-1-yl)-4-(4-fluorophenyl)-1H-1,2,4-triazole-5(4H)-thione, C18H20FN3S

C18H20FN3S, triclinic, P1̅, a = 7.3884(4) Å, b = 10.0741(6) Å, c = 12.6533(8) Å, α = 69.209(2)°, β = 73.778(2)°, γ = 72.638(2)°, V = 824.33(8) Å3, Z = 2, Rgt(F) = 0.0480, wRref(F2) = 0.1351, T = 296(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.

Adamantyl metal complexes: new routes to adamantyl anions and new transmetallations

New routes to 1- and 2-adamantyl anion equivalents are described, starting from commercially available 1- and 2-adamantylzinc bromides and employing reducing metals (Mg; Li). Adamantylmagnesium bromides (both 1-AdMgBr and 2-AdMgBr) can reliably be produced via reaction of the corresponding adamantylzinc bromides with excess magnesium metal. Reactions of adamantylzinc bromides with stoichiometic lithium biphenylide or lithium 2,2'-bipyridylide afford the new diadamantylzinc species, 1-Ad₂Zn and 2-Ad₂Zn, isolable free of solvent and salt impurities. Addition of 2,2'-bipyridine (bipy) leads to the crystalline adducts 1-Ad₂Zn(bipy) and 2-Ad₂Zn(bipy), which were structurally characterized. The resulting adamantyl anions were used in order to generate the first adamantyl complexes of mercury (1- and 2-Ad₂Hg), gold (1- and 2-AdAu(PPh₃), 1- and 2-AdAu(PCy₃)) and bismuth (2-Ad₂BiBr), of which 1- and 2-Ad₂Hg, 2-AdAu(PPh₃), 2-AdAu(PCy₃), and 2-Ad₂BiBr were isolated. These include the first structurally characterized unsupported 2-adamantyl metal complexes.

Adamantane-Isothiourea Hybrid Derivatives: Synthesis, Characterization, In Vitro Antimicrobial, and In Vivo Hypoglycemic Activities

A new series of adamantane-isothiourea hybrid derivatives, namely 4-arylmethyl (Z)-N'-(adamantan-1-yl)-morpholine-4-carbothioimidates 7a-e and 4-arylmethyl (Z)-N'-(adamantan-1-yl)-4-phenylpiperazine-1-carbothioimidates 8a-e were prepared via the reaction of N-(adamantan-1-yl)morpholine-4-carbothioamide 5 and N-(adamantan-1-yl)-4-phenylpiperazine-1-carbothioamide 6 with benzyl or substituted benzyl bromides, in acetone, in the presence of anhydrous potassium carbonate. The structures of the synthesized compounds were confirmed by ¹H-NMR, ¹³C-NMR, electrospray ionization mass spectral (ESI-MS) data, and X-ray crystallographic data. The in vitro antimicrobial activity of the new compounds was determined against certain standard strains of pathogenic bacteria and the yeast-like pathogenic fungus Candida albicans. Compounds 7b, 7d and 7e displayed potent broad-spectrum antibacterial activity, while compounds 7a, 7c, 8b, 8d and 8e were active against the tested Gram-positive bacteria. The in vivo oral hypoglycemic activity of the new compounds was carried on streptozotocin (STZ)-induced diabetic rats. Compounds 7a, 8ab, and 8b produced potent dose-independent reduction of serum glucose levels, compared to the potent hypoglycemic drug gliclazide.

Discovery and pharmacological evaluation of a novel series of adamantyl cyanoguanidines as P2X7 receptor antagonists

Here we report adamantyl cyanoguanidine compounds based on hybrids of the adamantyl amide scaffold reported by AstraZeneca and cyanoguanidine scaffold reported by Abbott Laboratories. Compound 27 displayed five-fold greater inhibitory potency than the lead compound 2 in both pore-formation and interleukin-1β release assays, while 35-treated mice displayed an antidepressant phenotype in behavioral studies. This SAR study provides a proof of concept for hybrid compounds, which will help in the further development of P2X₇R antagonists.

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).

Adamantane in Drug Delivery Systems and Surface Recognition

The adamantane moiety is widely applied in design and synthesis of new drug delivery systems and in surface recognition studies. This review focuses on liposomes, cyclodextrins, and dendrimers based on or incorporating adamantane derivatives. Our recent concept of adamantane as an anchor in the lipid bilayer of liposomes has promising applications in the field of targeted drug delivery and surface recognition. The results reported here encourage the development of novel adamantane-based structures and self-assembled supramolecular systems for basic chemical investigations as well as for biomedical application.

Analogues of desferrioxamine B designed to attenuate iron-mediated neurodegeneration: synthesis, characterisation and activity in the MPTP-mouse model of Parkinson's disease

One dual-function (2) and one first-generation (9) conjugate of the Fe(iii) chelator desferrioxamine B (DFOB,1) showed significant rescue of neurons in the MPTP mouse model of Parkinson's disease.

1-Adamantylamine a simple urine marker for screening for third generation adamantyl-type synthetic cannabinoids by ultra-performance liquid chromatography tandem mass spectrometry

Background

Synthetic cannabinoids (NOIDS) are novel psychotropic drugs (NPS) currently freely sold in the United Kingdom as ‘research chemicals’. Detection of NOIDS use is not available in current routine methods. Here we describe a marker which helps determine which patients have used these substances.

Methods

In a test case, ultra-performance liquid chromatography mass spectrometry (UPLC-Tof) was used to screen the legal high Herbal Haze II, the contents of hand-rolled cigarettes and five patient samples for NOIDS and their metabolites.

Results

Analysis of legal high Herbal Haze II and cigarettes identified the third generation adamantyl-type NOIDS N-(1-adamantyl)-1-pentyl-1H-indazole-3-carboxamide (AKB-48), 5F-AKB-48 and N-adamantyl-1-fluoropentylindole-3-carboxamide (STS-135). Out of 18 potential metabolites, 1-adamantylamine (C10H17N) was detected in all five urine samples. This adamantyl-type NOID marker was incorporated into our routine LC-MS/MS urine screen. Out of 14,436 random urine samples screened over eight months, 296 (2.05%) tested positive for the adamantyl-type NOID marker.

Conclusion

We have discovered a urine marker for identifying patients smoking legal high products containing the third generation adamantyl-type NOIDS such as AKB-48 and its fluoropentyl analogue 5F-AKB-48, which are among the most popular NOIDS currently available in legal high products sold in UK. This marker can be incorporated into routine LC-MS/MS drug screening alongside classic drugs of abuse. Positive detection rates for this new legal high marker are greater than for established classic drugs that are routinely screened such as amphetamine. This work highlights the need for a flexible toxicology screening service capable of adapting to changes in drug use such as the growing popularity of legal highs/NPS.

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 N′-(adamantan-2-ylidene)pyridine-3-carbohydrazide, C16H19N3O

C16H19N3O, orthorhombic, Pna21 (no. 33), a = 8.0381(5) Å, b = 10.4499(8) Å, c = 17.1228(13) Å, V = 438.27(18) Å, Z = 4, Rgt(F) = 0.0499, wRref(F2) = 0.1105, T = 100 K.

Development of a Fluorinated Class-I HDAC Radiotracer Reveals Key Chemical Determinants of Brain Penetrance

Despite major efforts, our knowledge about many brain diseases remains remarkably limited. Epigenetic dysregulation has been one of the few leads toward identifying the causes and potential treatments of psychiatric disease over the past decade. A new positron emission tomography radiotracer, [(11)C]Martinostat, has enabled the study of histone deacetylase in living human subjects. A unique property of [(11)C]Martinostat is its profound brain penetrance, a feature that is challenging to engineer intentionally. In order to understand determining factors for the high brain-uptake of Martinostat, a series of compounds was evaluated in rodents and nonhuman primates. The study revealed the major structural contributors to brain uptake, as well as a more clinically relevant fluorinated HDAC radiotracer with comparable behavior to Martinostat, yet longer half-life.

Combinatorial phenotypic screen uncovers unrecognized family of extended thiourea inhibitors with copper-dependent anti-staphylococcal activity

The continuous rise of multi-drug resistant pathogenic bacteria has become a significant challenge for the health care system. In particular, novel drugs to treat infections of methicillin-resistant Staphylococcus aureus strains (MRSA) are needed, but traditional drug discovery campaigns have largely failed to deliver clinically suitable antibiotics. More than simply new drugs, new drug discovery approaches are needed to combat bacterial resistance. The recently described phenomenon of copper-dependent inhibitors has galvanized research exploring the use of metal-coordinating molecules to harness copper's natural antibacterial properties for therapeutic purposes. Here, we describe the results of the first concerted screening effort to identify copper-dependent inhibitors of Staphylococcus aureus. A standard library of 10 000 compounds was assayed for anti-staphylococcal activity, with hits defined as those compounds with a strict copper-dependent inhibitory activity. A total of 53 copper-dependent hit molecules were uncovered, similar to the copper independent hit rate of a traditionally executed campaign conducted in parallel on the same library. Most prominent was a hit family with an extended thiourea core structure, termed the NNSN motif. This motif resulted in copper-dependent and copper-specific S. aureus inhibition, while simultaneously being well tolerated by eukaryotic cells. Importantly, we could demonstrate that copper binding by the NNSN motif is highly unusual and likely responsible for the promising biological qualities of these compounds. A subsequent chemoinformatic meta-analysis of the ChEMBL chemical database confirmed the NNSNs as an unrecognized staphylococcal inhibitor, despite the family's presence in many chemical screening libraries. Thus, our copper-biased screen has proven able to discover inhibitors within previously screened libraries, offering a mechanism to reinvigorate exhausted molecular collections.

Crystal structure of 5-(adamantan-1-yl)-3-[(4-chloroanilino)methyl]-2,3-dihydro-1,3,4-oxadiazole-2-thione, C19H22ClN3OS

C19H22ClN3OS, orthorhombic, P212121 (no. 19), a = 7.0418(2) Å, b = 10.8802(3) Å, c = 23.5506(6) Å, V = 1804.36(8) Å3, Z = 4, R gt (F) = 0.0413, wR ref (F 2 ) = 0.1110, T = 100 K.

Catalyst-free multicomponent synthesis of novel adamantyl-containing tetrahydropyrimidine carboxylates

[Formula: see text]-Enaminoesters were generated in situ by the reaction of aliphatic or aromatic primary amines to electron-deficient alkynes, dimethyl acetylenedicarboxylate, and methyl propiolate. [Formula: see text]-Enaminoesters thus formed were reacted with 1-adamantanamine and formaldehyde in methanol to give novel molecular hybrids: dimethyl 3-((3s,5s,7s)-adamantan-1-yl)-1-(alkyl/aralkyl/aryl)-1,2,3,4-tetrahydropyrimidine-5,6-dicarboxylates (5a-j) and methyl 3-((3s,5s,7s)-adamantan-1-yl)-1-(alkyl/aralkyl/aryl)-1,2,3,4-tetrahydropyrimidine-5-carboxylates (9a-j). The structures of the molecular hybrids have been established based on the spectral and analytical data. Structural confirmation of the products was done by X-ray crystallography of 5d as a representative product of the series.

Magnesium(ii) 1-(1-adamantylsulfanyl)phthalocyanine – synthesis, photochemical and electrochemical properties

Phthalocyanine with moderate fluorescence and singlet oxygen quantum yield was obtained and its electrochemical properties were assessed.

Polycationic adamantane-based dendrons form nanorods in complex with plasmid DNA

Different HYDRAmers are synthesized and complexed to a model plasmid DNA. Appropriate chemical modifications can improve efficiently the complexation to get HYDRAplexes, in form of long nanorods, with very good DNA binding and protecting properties.