Cholinesterase Inhibitory Activities of Adamantyl-Based Derivatives and Their Molecular Docking Studies.

Adamantyl-based compounds are clinically important for the treatments of type 2 diabetes and for their antiviral abilities, while many more are under development for other pharmaceutical uses. This study focused on the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of adamantyl-based ester derivatives with various substituents on the phenyl ring using Ellman's colorimetric method. Compound 2e with a 2,4-dichloro electron-withdrawing substituent on the phenyl ring exhibited the strongest inhibition effect against AChE, with an IC50 value of 77.15 µM. Overall, the adamantyl-based ester with the mono-substituent at position 3 of the phenyl ring exhibited good AChE inhibition effects with an ascending order for the substituents: Cl < NO2 < CH3 < OCH3. Furthermore, compounds with electron-withdrawing groups (Cl and NO2) substituted at position 3 on their phenyl rings demonstrated stronger AChE inhibition effects, in comparison to their respective positional isomers. On the other hand, compound 2j with a 3-methoxyphenyl ring showed the highest inhibition effect against BChE, with an IC50 value of 223.30 µM. Molecular docking analyses were conducted for potential AChE and BChE inhibitors, and the results demonstrated that the peripheral anionic sites of target proteins were predominant binding sites for these compounds through hydrogen bonds and halogen interactions instead of hydrophobic interactions in the catalytic active site.

Synthesis and Crystallographic Insight into the Structural Aspects of Some Novel Adamantane-Based Ester Derivatives.

Adamantyl-based compounds are commercially important in the treatments for neurological conditions and type-2 diabetes, aside from their anti-viral abilities. Their values in drug design are chronicled as multi-dimensional. In the present study, a series of 2-(adamantan-1-yl)-2-oxoethyl benzoates, 2(a-q), and 2-(adamantan-1-yl)-2-oxoethyl 2-pyridinecarboxylate, 2r, were synthesized by reacting 1-adamantyl bromomethyl ketone with various carboxylic acids using potassium carbonate in dimethylformamide medium at room temperature. Three-dimensional structures studied using X-ray diffraction suggest that the adamantyl moiety can serve as an efficient building block to synthesize 2-oxopropyl benzoate derivatives with synclinal conformation with a looser-packed crystal packing system. Compounds 2a, 2b, 2f, 2g, 2i, 2j, 2m, 2n, 2o, 2q and 2r exhibit strong antioxidant activities in the hydrogen peroxide radical scavenging test. Furthermore, three compounds, 2p, 2q and 2r, show good anti-inflammatory activities in the evaluation of albumin denaturation.

Benzofuranyl Esters: Synthesis, Crystal Structure Determination, Antimicrobial and Antioxidant Activities.

A series of five new 2-(1-benzofuran-2-yl)-2-oxoethyl 4-(un/substituted)benzoates 4(a-e), with the general formula of C8H5O(C=O)CH2O(C=O)C6H4X, X = H, Cl, CH3, OCH3 or NO2, was synthesized in high purity and good yield under mild conditions. The synthesized products 4(a-e) were characterized by FTIR, ¹H-, (13)C- and ¹H-(13)C HMQC NMR spectroscopic analysis and their 3D structures were confirmed by single-crystal X-ray diffraction studies. These compounds were screened for their antimicrobial and antioxidant activities. The tested compounds showed antimicrobial ability in the order of 4b < 4a < 4c < 4d < 4e and the highest potency with minimum inhibition concentration (MIC) value of 125 µg/mL was observed for 4e. The results of antioxidant activities revealed the highest activity for compound 4e (32.62% ± 1.34%) in diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, 4d (31.01% ± 4.35%) in ferric reducing antioxidant power (FRAP) assay and 4a (27.11% ± 1.06%) in metal chelating (MC) activity.

Crystal structure of dimeric flavodoxin from Desulfovibrio gigas suggests a potential binding region for the electron-transferring partner.

Flavodoxins, which exist widely in microorganisms, have been found in various pathways with multiple physiological functions. The flavodoxin (Fld) containing the cofactor flavin mononucleotide (FMN) from sulfur-reducing bacteria Desulfovibrio gigas (D. gigas) is a short-chain enzyme that comprises 146 residues with a molecular mass of 15 kDa and plays important roles in the electron-transfer chain. To investigate its structure, we purified this Fld directly from anaerobically grown D. gigas cells. The crystal structure of Fld, determined at resolution 1.3 Å, is a dimer with two FMN packing in an orientation head to head at a distance of 17 Å, which generates a long and connected negatively charged region. Two loops, Thr59-Asp63 and Asp95-Tyr100, are located in the negatively charged region and between two FMN, and are structurally dynamic. An analysis of each monomer shows that the structure of Fld is in a semiquinone state; the positions of FMN and the surrounding residues in the active site deviate. The crystal structure of Fld from D. gigas agrees with a dimeric form in the solution state. The dimerization area, dynamic characteristics and structure variations between monomers enable us to identify a possible binding area for its functional partners.

Synthesis and crystal structures of N-substituted pyrazolines.

Four pyrazole compounds, 3-(4-fluorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-1-carbaldehyde (1), 5-(4-bromophenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazole-1-carbaldehyde (2), 1-[5-(4-chlorophenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]ethanone (3) and 1-[3-(4-fluorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl]propan-1-one (4), have been prepared by condensing chalcones with hydrazine hydrate in the presence of aliphatic acids, namely formic acid, acetic acid and propionic acid. The structures were characterized by X-ray single crystal structure determination. The dihedral angles formed between the pyrazole and the fluoro-substituted rings are 4.64(7)° in 1, 5.3(4)° in 2 and 4.89(6)° in 3. In 4, the corresponding angles for molecules A and molecules B are 10.53(10)° and 9.78(10)°, respectively.

5-Bromo-4-(3,4-dimeth-oxy-phen-yl)thia-zol-2-amine.

In the title compound, C(11)H(11)BrN(2)O(2)S, the thia-zole ring makes a dihedral angle of 53.16 (11)° with the adjacent benzene ring. The two meth-oxy groups are slightly twisted from the attached benzene ring with C-O-C-C torsion angles of -9.2 (3) and -5.5 (3)°. In the crystal, mol-ecules are linked by a pair of N-H⋯N hydrogen bonds into an inversion dimer with an R(2) (2)(8) ring motif. The dimers are further connected by N-H⋯O hydrogen bonds into a tape along [-110].

(2E)-2-{[3-Methyl-5-(2-naphth-yloxy)-1-phenyl-1H-pyrazol-4-yl]methyl-idene}hydrazinecarbothio-amide monohydrate.

In the title compound, C(22)H(19)N(5)OS·H(2)O, the naphthalene ring system and the benzene ring [dihedral angle = 85.19 (8)°] make dihedral angles of 87.02 (9) and 14.41 (10)°, respectively, with the pyrazole ring. The mean plane through the 2-methyl-enehydrazinecarbothio-amide group [C-N-N-C(=S)-N; maximum deviation = 0.022 (1) Å] is slightly twisted from the pyrazole ring [dihedral angle = 5.60 (11)°]. In the crystal, mol-ecules are linked by N-H⋯S, N-H⋯O, O-H⋯S, O-H⋯N and C-H⋯S hydrogen bonds into sheets parallel to the ab plane. π-π inter-actions are also observed [centroid-to-centroid distances = 3.7778 (12) and 3.7010 (12) Å].

4-Benzyl-8-phenyl-1-thia-4-aza-spiro-[4.5]decan-3-one.

In the title compound, C(21)H(23)NOS, the thia-zolidine ring adopts a twist conformation about one of its C-S bonds, while the cyclo-hexane ring has a chair conformation. The S and N atoms attached to the spiro C atom are in axial and equatorial orientations, respectively. The thia-zolidine ring forms dihedral angles of 86.24 (14) and 31.82 (15)° with the directly attached and remote terminal benzene rings, respectively. The dihedral angle between the two terminal benzene rings is 86.74 (14)°. In the crystal, the only significant directional inter-action is a weak C-H⋯π bond, which generates [010] chains.

2-Anilino-4-(1,3-benzothia-zol-2-yl)-5-(4-chloro-benzo-yl)thio-phene-3-carbonitrile.

In the title compound, C(25)H(14)ClN(3)OS(2), the central thio-phene ring [maximum deviation = 0.011 (1) Å] makes dihedral angles of 55.72 (5), 13.36 (5) and 46.77 (4)° with the adjacent chloro-substituted benzene ring, the benzene ring and the 1,3-benzothia-zole ring system [maximum deviation = 0.012 (1) Å], respectively. An intra-molecular C-H⋯S(thienyl) hydrogen bond generates an S(6) ring motif in the mol-ecule. In the crystal, mol-ecules are linked by pairs of N-H⋯N hydrogen bonds into inversion dimers and the dimers are further connected by C-H⋯O hydrogen bonds into tapes running along [100]. Aromatic π-π stacking inter-actions are also observed [centroid-to-centroid distances = 3.6116 (6) and 3.7081 (6) Å].

4-Bromo-acetyl-3-phenyl-sydnone.

IN THE TITLE COMPOUND (SYSTEMATIC NAME: 4-bromoacetyl-1,2,3-oxadiazol-3-ylium-5-olate), C(10)H(7)BrN(2)O(3), the 1,2,3-oxadiazole ring and bromo-acetyl group are essentially planar [maximum deviation = 0.010 (4) and 0.013 (3) Šrespectively] and form dihedral angles of 59.31 (19) and 67.96 (11)°, respectively, with the phenyl ring. The 1,2,3-oxadiazole ring is twisted slightly from the mean plane of the bromo-acetyl group, forming a dihedral angle of 9.16 (24)°. In the crystal, mol-ecules are linked by pairs of weak C-H⋯O hydrogen bonds into inversion dimers with R(2) (2)(12) ring motifs. The dimers are further connected by weak C-H⋯O hydrogen bonds into an infinite tape parallel to the b axis. In addition, π-π stacking inter-actions [centroid-centroid distance = 3.6569 (19) Å] and short inter-molecular contacts [O⋯O = 2.827 (3) and C⋯C = 3.088 (5) Å] are observed.

2-[(1H-Benzimidazol-2-yl)sulfan-yl]-1-phenyl-ethanone.

The title compound, C(15)H(12)N(2)OS, adopts a twisted V-shape, with the S atom as the pivot. The benzimidazole ring system [maximum deviation = 0.015 (1) Å] makes a dihedral angle of 78.56 (7)° with the phenyl ring. The O atom of the ketone group is close to coplanar with its adjacent ring [O-C-C-C torsion angle = 11.0 (2)°]. In the crystal, mol-ecules are linked by N-H⋯N hydrogen bonds into an infinite chain along [001]. The crystal packing also features a C-H⋯π inter-action.

1-Chloro-1-[(Z)-2-phenyl-hydrazin-1-yl-idene]propan-2-one.

The title compound, C(9)H(9)ClN(2)O, is close to planar (r.m.s. deviation for the non-H atoms = 0.0446 Å); it exists in a cis conformation with respect to the C=N double bond. In the crystal, the ketone O atom accepts both N-H⋯O and C-H⋯O hydrogen bonds, which leads to [010] infinite chains incorporating R(2) (1)(6) loops. The crystal structure also features a C-H⋯π inter-action.

(E)-3-(4-Chloro-phen-yl)-1-(4-fluoro-phenyl)-prop-2-en-1-one.

In the title compound, C(15)H(10)ClFO, the fluoro-substituted benzene ring forms a dihedral angle of 44.41 (6)° with the chloro-substituted benzene ring. The only significant directional bonds in the crystal are weak C-H⋯π inter-actions.

2-[3,5-Bis-(4-fluoro-phen-yl)-4,5-dihydro-1H-pyrazol-1-yl]-4,6-bis(4-fluoro-phenyl)pyrimidine.

In the title compound, C(31)H(20)F(4)N(4), the pyrazole ring adopts an envelope conformation and forms a dihedral angle of 9.91 (6)° with the adjacent pyrimidine ring. The pyrimidine ring forms dihedral angles of 9.23 (6) and 2.16 (5)° with its adjacent fluoro-substituted benzene rings, whereas these angles are 88.22 (6) and 9.66 (6)° for the pyrazole ring and its adjacent benzene rings. In the crystal, mol-ecules are linked by C-H⋯F hydrogen bonds into ribbons along [01-1]. The crystal packing is further stabilized by C-H⋯π and by π-π inter-actions, with centroid-centroid distances of 3.7428 (7) and 3.7630 (6) Å.

3,3'-[1,4-Phenyl-enebis(methyl-ene)]-bis-(1-propyl-benzimidazolium) dichloride dihydrate.

The asymmetric unit of the title compound, C(28)H(32)N(4) (2+)·2Cl(-)·2H(2)O, contains half of a 3,3'-[1,4-phenyl-enebis(methyl-ene)]bis-(1-propyl-benzimidazolium) cation, one chloride anion and one water mol-ecule. The complete cation is generated by a crystallographic inversion center. The central benzene ring forms a dihedral angle of 66.06 (11)° with its adjacent benzimidazolium ring system. In the crystal, the cations, anions and water mol-ecules are linked by O-H⋯Cl, C-H⋯O and C-H⋯Cl hydrogen bonds into a three-dimensional network. The crystal packing is further stabilized by π-π inter-actions, with centroid-centroid distances of 3.5561 (15) and 3.6708 (15) Å.

(E)-N'-(4-Meth-oxy-benzyl-idene)-2-(2-methyl-4-nitro-1H-imidazol-1-yl)acetohydrazide.

In the title compound, C(14)H(15)N(5)O(4), the central -C=N-N-C(=O)-C- bridge is nearly planar [maximum deviation = 0.037 (1) Å] and forms dihedral angles of 7.37 (9) and 73.33 (5)°, respectively, with the benzene and imidazole rings. The dihedral angle between the benzene and imidazole rings is 66.08 (9)°. The meth-oxy and nitro groups are nearly coplanar with the benzene and imidazole rings, respectively, with a C-O-C-C torsion angle of 5.9 (2)° and an O-N-C-C angle of -0.2 (2)°. In the crystal, mol-ecules are linked by a pair of N-H⋯O hydrogen bonds with an R(2) (2)(8) ring motif, forming an inversion dimer. The dimers are further inter-connected by C-H⋯O hydrogen bonds into a sheet parallel to the (111) plane. A C-H⋯π inter-action is also observed between the sheets.

Ethyl 4,4''-difluoro-5'-meth-oxy-1,1':3',1''-terphenyl-4'-carboxyl-ate.

In the title compound, C(22)H(18)F(2)O(3), the two fluoro-substituted rings form dihedral angles of 25.89 (15) and 55.00 (12)° with the central benzene ring. The eth-oxy group in the mol-ecule is disordered over two positions with a site-occupancy ratio of 0.662 (7):0.338 (7). In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds into chains along the a axis. The crystal packing is further stabilized by C-H⋯π and π-π inter-actions, with centroid-centroid distances of 3.8605 (15) Å.

N-[(4-Methyl-phen-yl)sulfon-yl]acetamide.

In the title compound, C(9)H(11)NO(3)S, the dihedral angle between the benzene ring and the amide group is 76.7 (3)°. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds into inversion dimers with R(2) (2)(8) ring motifs. The dimers are further connected by N-H⋯O and C-H⋯O hydrogen bonds into an infinite tape running parallel to the b-axis direction.

(2E)-3-(3-Nitro-phen-yl)-1-[4-(piperidin-1-yl)phen-yl]prop-2-en-1-one.

In the title compound, C(20)H(20)N(2)O(3), the piperidine ring adopts a chair conformation and its mean plane forms dihedral angles of 19.63 (9) and 19.44 (9)°, respectively, with the benzene and the nitro-substituted benzene ring. The benzene and nitro-substituted benzene rings are almost coplanar and make a dihedral angle of 4.78 (8)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds into two-dimensional networks parallel to the ab plane. The crystal packing is further stabilized by π-π inter-actions [maximum centroid-centroid distance = 3.7807 (12) Å].

N-(2,6-Dimethyl-phen-yl)-2,2-diphenyl-acetamide.

In the title compound, C(22)H(21)NO, the dihedral angle between the phenyl rings is 82.59 (7)°. The dimethyl-benzene ring forms dihedral angles of 52.86 (4) and 49.65 (5)° with the two phenyl rings. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, forming a C(4) chain along the c axis. The crystal also features C-H⋯π inter-actions.