Synthesis and cholinesterase inhibition of cativic acid derivatives.

Alzheimer's disease (AD) is a neurodegenerative disorder associated with memory impairment and cognitive deficit. Most of the drugs currently available for the treatment of AD are acetylcholinesterase (AChE) inhibitors. In a preliminary study, significant AChE inhibition was observed for the ethanolic extract of Grindelia ventanensis (IC50=0.79 mg/mL). This result prompted us to isolate the active constituent, a normal labdane diterpenoid identified as 17-hydroxycativic acid (1), through a bioassay guided fractionation. Taking into account that 1 showed moderate inhibition of AChE (IC50=21.1 µM), selectivity over butyrylcholinesterase (BChE) (IC50=171.1 µM) and that it was easily obtained from the plant extract in a very good yield (0.15% w/w), we decided to prepare semisynthetic derivatives of this natural diterpenoid through simple structural modifications. A set of twenty new cativic acid derivatives (3-6) was prepared from 1 through transformations on the carboxylic group at C-15, introducing a C2-C6 linker and a tertiary amine group. They were tested for their inhibitory activity against AChE and BChE and some structure-activity relationships were outlined. The most active derivative was compound 3c, with an IC50 value of 3.2 µM for AChE. Enzyme kinetic studies and docking modeling revealed that this inhibitor targeted both the catalytic active site and the peripheral anionic site of this enzyme. Furthermore, 3c showed significant inhibition of AChE activity in SH-SY5Y human neuroblastoma cells, and was non-cytotoxic.

Crystal structure of 4,4'-(disulfanediyl)dibutanoic acid-4,4'-bipyridine (1/1).

4,4'-(Disulfanediyl)dibutanoic acid (dtba) and 4,4'-bipyridine (4,4'-bpy) crystallize in an 1:1 ratio, leading to the title co-crystal with composition C8H14O4S2·C10H8N2. A distinctive feature of the crystal structure is the geometry of the dtba moiety, which appears to be stretched [with a 9.98 (1) Šspan between outermost carbons] and acts as an hydrogen-bonding connector, forming linear chains along [-211] with the 4,4'-bpy moiety by way of O-H⋯N hydrogen bonds and C-H⋯O interactions. The influence of the mol-ecular shape on the hydrogen-bonding pattern is analysed by comparing the title compound and two other 4,4'-bpy co-crystals with closely related mol-ecules of similar formulation but different geometry, showing the way in which this correlates with the packing arrangement.

Crystal structure of zwitterionic 4-(ammonio-methyl)-benzoate: a simple mol-ecule giving rise to a complex supra-molecular structure.

The asymmetric unit of the title compound, C8H9NO2·H2O consists of an isolated 4-(ammonio-meth-yl)benzoate zwitterion derived from 4-amino-methyl-benzoic acid through the migration of the acidic proton, together with a water molecule of crystallization that is disordered over three sites with occupancy ratios (0.50:0.35:0.15). In the crystal structure, N-H⋯O hydrogen bonds together with π-π stacking of the benzene rings [centroid-centroid distance = 3.8602 (18) Å] result in a strongly linked, compact three-dimensional structure.

Synthesis, crystal structure, magnetic behaviour and thermal stability of a paddle-wheel copper(II) complex bearing equatorial 3,4-diethoxybenzoate ligands.

The binuclear paddle-wheel copper(II) complex tetrakis(µ-3,4-diethoxybenzoato-κ2O:O')bis[(ethanol-κO)copper(II)], [Cu2(C11H13O4)4(C2H6O)2], has been synthesized and characterized. In each molecule, two CuII centres are bridged in a syn-syn fashion by four equatorial 3,4-diethoxybenzoate ligands, the two axial positions being occupied by ethanol molecules. The thermal stability has been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The magnetic behaviour, studied by SQUID magnetometry, shows a CuII-CuII antiferromagnetic exchange interaction with 2J = -288 cm-1, a value that fits with a magnetic structure correlation established for compounds of this kind.

Aripiprazole salts. III. Bis(aripiprazolium) oxalate-oxalic acid (1/1).

The asymmetric unit of the title salt [systematic name: bis(4-(2,3-dichlorophenyl)-1-{4-[(2-oxo-1,2,3,4-tetrahydroquinolin-7-yl)oxy]butyl}piperazin-1-ium) oxalate-oxalic acid (1/1)], 2C(23)H(28)Cl(2)N(3)O(2)(+)·C(2)O(4)(2-)·C(2)H(2)O(4), consists of one protonated aripiprazole unit (HArip(+)), half an oxalate dianion and half an oxalic acid molecule, the latter two lying on inversion centres. The conformation of the HArip(+) cation differs from that in other reported salts and resembles more the conformation of neutral Arip units in reported polymorphs and solvates. The intermolecular interaction linking HArip(+) cations is also similar to those in reported Arip compounds crystallizing in the space group P1, with head-to-head N-H···O hydrogen bonds generating centrosymmetric dimers, which are further organized into planar ribbons parallel to (012). The oxalate anions and oxalic acid molecules form hydrogen-bonded chains running along [010], which 'pierce' the planar ribbons, interacting with them through a number of stronger N-H···O and weaker C-H···O hydrogen bonds, forming a three-dimensional network.

The supramolecular structure of a cadmium complex with the new functionalized terpyridine ligand 4'-[4-(pyrimidin-5-yl)phenyl]-2,2':6',2''-terpyridine (L1): aqua(L1-κ³N,N',N'')(nitrato-κ²O,O')(nitrato-κO)cadmium(II) dihydrate.

The monomeric title compound, aqua(nitrato-κ²O,O')(nitrato-κO){4'-[4-(pyrimidin-5-yl)phenyl]-2,2':6',2''-terpyridine-κ³N,N',N''}cadmium(II) dihydrate, [Cd(NO3)2(C25H17N5)(H2O)]·2H2O, consists of a seven-coordinated CdII centre bound to the novel 4'-[4-(pyrimidin-5-yl)phenyl]-2,2':6',2''-terpyridine (L1) ligand (behaving as a tridentate chelate), two nitrate anions (as chelating-bidentate and monodentate ligands) and a water O atom. Both chelating groups define the base of a slightly deformed pentagonal bipyramid, while the monocoordinated ligands occupy the apices. The four heterocycles in L1 form a planar skeleton, while the central benzene ring is rotated from this planar geometry by more than 30°, probably because of packing effects. Noncovalent interactions lead to the formation of columnar arrays parallel to [100].

Two isomorphous transition metal complexes displaying a coordinated tetrathionate unit: bis(4,4'-dimethyl-2,2'-bipyridine-κ(2)N,N')(tetrathionato-κ(2)S,S')cadmium(II) dimethylformamide disolvate and the zinc(II) analogue.

The isomorphous title compounds, [Tr(S4O6)(C12H12N2)2]·2C3H7NO (Tr = Cd(II) and Zn(II)), consist of metal centres to which one tetrathionate and two 4,4'-dimethyl-2,2'-bipyridine chelating ligands bind. The structures are completed by two symmetry-related dimethylformamide solvent molecules. Each metal-centred complex is bisected by a twofold axis running through the metal centre and halving the chelating tetrathionate dianion through the central S-S bond. The ancillary symmetry-related 4,4'-dimethyl-2,2'-bipyridine ligands act as chelates. This results in a distorted six-coordinate geometry, with similar Tr-O/N distances but central angles differing substantially from 90 and 180°. Both ligands are basically featureless from a geometric point of view, with torsion angles in both coordinated tetrathionate groups suggesting a trend linking metal size (covalent radius) and ligand `openness'. Packing is directed by (C-H)aromatic···O bridges and π-π offset stacked interactions defining chains along [001], further linked by weaker (C-H)methyl···O bridges, some of them mediated by the dimethylformamide solvent molecules.

An anisaldehyde sodium bisulfite derivative: poly[[µ4-(hydroxy)(4-methoxyphenyl)methanesulfonato]sodium].

The title complex, [Na(C(8)H(9)O(5)S)](n), is polymeric and consists of broad layers parallel to (100) made up of an inner hydrophilic core of Na(+) cations and polar SO(3)C(OH)- groups, padded on both sides by two hydrophobic layers of pendant methoxyphenyl groups. The Na(+) cations in the inner core are six-coordinated into highly distorted NaO(6) octahedra by four symmetry-related (hydroxy)(4-methoxyphenyl)methanesulfonate anions, leading to a tightly woven two-dimensional structure. While there are some hydrogen bonds providing interplanar cohesion, interactions between adjacent layers are weak hydrophobic ones. The present compound appears to be the first reported structure containing the (hydroxy)(4-methoxyphenyl)methanesulfonate ligand.

A new polymorph of bis[2,6-bis(1H-benzimidazol-2-yl-κN3)pyridinido-κN]zinc(II).

The title compound, [Zn(C(19)H(12)N(5))(2)], crystallizes in the tetragonal space group P4(3)2(1)2, with the monomer residing on a twofold axis. The imidazole N-bound H atoms are disordered over the two positions, with refined occupancies of 0.59 (3) and 0.41 (3). The strong similarities to, and slight differences from, a reported P4(2)2(1)2 polymorph which has a 50% smaller unit-cell volume [Harvey, Baggio, Muñoz & Baggio (2003). Acta Cryst. C59, m283-m285], to which the present structure bears a group-subgroup relationship, are discussed.

Tetraaqua(4,4'-dimethyl-2,2'-bipyridine-κ2N,N')nickel(II) sulfate monohydrate: a simple molecule with an extremely complex hydrogen-bonding scheme.

The title ionic compound, [Ni(C12H12N2)(H2O)4]SO4·H2O, is composed of an Ni(II) cation coordinated by a chelating 4,4'-dimethyl-2,2'-bipyridine ligand via its two N atoms [mean Ni-N = 2.056 (2) Å] and by four aqua ligands [mean Ni-O = 2.073 (9) Å], the net charge being balanced by an external sulfate anion. The whole structure is stabilized by a solvent water molecule. Even though the individual constituents are rather featureless, they generate an extremely complex supramolecular structure consisting of a central hydrogen-bonded two-dimensional hydrophilic nucleus made up of complex cations, sulfate anions and coordinated and solvent water molecules, with pendant hydrophobic 4,4'-dimethyl-2,2'-bipyridine ligands which interact laterally with their neighbours via π-π interactions. The structure is compared with closely related analogues in the literature.

A dense hydrogen-bonding network and an unusually large packing index in triaquatris(2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylato)neodymium(III) trihydrate.

The title mononuclear complex, [Nd(C5H3N2O3)3(H2O)3]·3H2O, consists of an Nd(III) cation, three 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate ligands and three aqua ligands forming the neutral complex molecule, and three solvent water molecules. The pyrimidinecarboxylate ligands act in a chelating manner, via carboxylate and keto O atoms. The NdO9 coordination polyhedron is in the form of a distorted monocapped square antiprism. The availability of numerous hydrogen-bonding donors and acceptors results in a very dense hydrogen-bonding network, the immediate effect of which is an unusually large packing index.

Three transition-metal complexes with the macrocyclic ligand meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L): [Cu(ClO4)2(L)], [Zn(NO3)2(L)] and [CuCl(L)(H2O)]Cl.

The three transition-metal complexes, (meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-κ4N)bis(perchlorato-κO)copper(II), [Cu(ClO4)2(C18H40N4)], (I), (meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-κ4N)bis(nitrato-κO)zinc(II), [Zn(NO3)2(C18H40N4)], (II), and aquachlorido(meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-κ4N)copper(II) chloride, [CuCl(C18H40N4)(H2O)]Cl, (III), are described. The molecules display a very similarly distorted 4+2 octahedral environment for the cation [located at an inversion centre in (I) and (II)], defined by the macrocycle N4 group in the equatorial sites and two further ligands in trans-axial positions [two O-ClO3 ligands in (I), two O-NO2 ligands in (II) and one chloride and one aqua ligand in (III)]. The most significant difference in molecular shape resides in these axial ligands, the effect of which on the intra- and intermolecular hydrogen bonding is discussed. In the case of (I), all strong hydrogen-bond donors are saturated in intramolecular interactions, while weak intermolecular C-H∙∙∙O contacts result in a three-dimensional network. In (II) and (III), instead, there are N-H and O-H donors left over for intermolecular interactions, giving rise to the formation of strongly linked but weakly interacting chains.

Two solvatomorphic forms of a copper complex formulated as Cu(L(1))(ClO4)2·1.2H2O and Cu(L(1))(ClO4)2, where L(1) is 3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane.

Two copper complex solvatomorphs, namely (3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane)bis(perchlorato-κO)copper(II) 1.2-hydrate, [Cu(ClO4)2(C18H40N4)]·1.2H2O, (I), and (3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane)bis(perchlorato-κO)copper(II), [Cu(ClO4)2(C18H40N4)], (II), are described and compared with each other and with a third, already reported, anhydrous diastereomer, denoted (III). Both compounds present very similar centrosymmetic coordination environments, with the Cu(II) cation lying on an inversion centre in a distorted 4+2 octahedral environment, defined by the macrocyclic N4 group in the equatorial sites and two perchlorate groups in trans-axial positions [one of the perchlorate ligands in (I) is partially disordered]. The most significant difference in molecular shape is seen in the orientation of the perchlorate anions, and the influence of this on the intramolecular hydrogen bonding is discussed. The (partially) hydrated state of (I) favours the formation of chains along [011], while the anhydrous character of (II) and (III) promotes loosely bound structures with low packing indices.

A polymeric cobalt(II) complex derived from citric acid (H4cit) and 2,6-diaminopurine (dap): {[Co4(cit)2(dap)4(H2O)4]·6.35H2O}n.

Poly[[tetraaquadi-µ4-citrato-tetrakis(2,6-diaminopurine)tetracobalt(II)] 6.35-hydrate], {[Co4(C6H4O7)2(C5H6N6)4(H2O)4]·6.35H2O}n, presents three different types of Co(II) cations in the asymmetric unit, two of them lying on symmetry elements (one on an inversion centre and the other on a twofold axis). The main fragment is further composed of one fully deprotonated citrate (cit) tetraanion, two 2,6-diaminopurine (dap) molecules and two aqua ligands. The structure is completed by a mixture of fully occupied and disordered solvent water molecules. The two independent dap ligands are neutral and the cit tetraanion provides for charge balance, compensating the 4+ cationic charge. There are two well defined coordination geometries in the structure. The simplest is mononuclear, with the Co(II) cation arranged in a regular centrosymmetric octahedral array, coordinated by two aqua ligands, two dap ligands and two O atoms from the ß-carboxylate groups of the bridging cit tetraanions. The second, more complex, group is trinuclear, bisected by a twofold axis, with the metal centres coordinated by two cit tetraanions through their α- and ß-carboxylate and α-hydroxy groups, and by two dap ligands bridging through one of their pyridine and one of their imidazole N atoms. The resulting coordination geometry around each metal centre is distorted octahedral. Both groups are linked alternately to each other, defining parallel chains along [201], laterally interleaved and well connected via hydrogen bonding to form a strongly coupled three-dimensional network. The compound presents a novel µ4-κ(5)O:O,O':O',O'',O''':O'''' mode of coordination of the cit tetraanion.

Relative influence of noncovalent interactions on the melting points of a homologous series of 1,2-dibromo-4,5-dialkoxybenzenes.

Crystal structures are presented for two members of the homologous series of 1,2-dibromo-4,5-dialkoxybenzenes, viz. those with decyloxy and hexadecyloxy substituents, namely 1,2-dibromo-4,5-bis(decyloxy)benzene, C(26)H(44)Br(2)O(2), (II), and 1,2-dibromo-4,5-bis(hexadecyloxy)benzene, C(38)H(68)Br(2)O(2), (III). The relative influences which halogen bonding, π-π stacking and van der Waals interactions have on these structures are analysed and the results compared with those already found for the lightest homologue, 1,2-dibromo-4,5-dimethoxybenzene, (I) [Cukiernik, Zelcer, Garland & Baggio (2008). Acta Cryst. C64, o604-o608]. The results confirm that the prevalent interactions stabilizing the structures of (II) and (III) are van der Waals contacts between the aliphatic chains. In the case of (II), weak halogen C-Br···(Br-C)' interactions are also present and contribute to the stability of the structure. In the case of (III), van der Waals interactions between the aliphatic chains are almost exclusive, weaker C-Br···π interactions being the only additional interactions detected. The results are in line with commonly accepted models concerning trends in crystal stability along a homologous series (as measured by their melting points), but the earlier report for n = 1, and the present report for n = 10 and 16, are among the few providing single-crystal information validating the hypothesis.

Two complexes derived from the reaction of M3(CO)12 clusters (M = Ru, Os) with the 9-(triphenylphosphonio)fluorenide ylide: tricarbonyl[9-(triphenylphosphonio)fluorenylidene]ruthenium and nonacarbonyl-µ3-fluorenylidene-µ2-hydrido-triangulo-triosmium(III).

Tricarbonyl[9-(triphenylphosphonio)fluorenylidene]ruthenium, [Ru(C31H21P)(CO)3], (I), is mononuclear, consisting of a single Ru centre, to which three carbonyl units and a chelating µ3-9-(triphenylphosphonio)fluorenide ylide bind to generate a distorted octahedral RuC6 core. Nonacarbonyl-µ3-fluorenylidene-µ2-hydrido-triangulo-triosmium(III), [Os3H(C13H7)(CO)9], (II), is trinuclear and presents a triangular triosmium core, nine carbonyl ligands and one fluorenylidene ligand. Two of the Os(III) centres present a highly distorted hexacoordinated Os(Os2C4) core and are in turn bridged by a hydride ligand. The remaining Os(III) cation is octacoordinated, with an Os(Os2C6) nucleus. The crystal structures of both compounds are the result of nondirectional forces, much resembling the packing of weakly interacting quasi-spherical units, viz. the molecules themselves in (I) and centrosymmetric π-π-bonded dimers in (II).

A polymorphic form of 4,4-dimethyl-8-methylene-3-azabicyclo[3.3.1]non-2-en-2-yl 3-indolyl ketone, an indole alkaloid extracted from Aristotelia chilensis (maqui).

The title compound [systematic name: (4,4-dimethyl-8-methylene-3-azabicyclo[3.3.1]non-2-en-2-yl)(1H-indol-3-yl)methanone], C20H22N2O, (II), was obtained from mother liquors extracted from Aristotelia chilensis (commonly known as maqui), a native Chilean tree. The compound is a polymorphic form of that obtained from the same source and reported by Watson, Nagl, Silva, Cespedes & Jakupovic [Acta Cryst. (1989), C45, 1322-1324], (Ia). The molecule consists of an indolyl ketone fragment and a nested three-ring system, with both groups linked by a C-C bridge. Comparison of both forms shows that they do not differ in their gross features but in the relative orientation of the two ring systems, due to different rotations around the bridge, as measured by the O=C-C=N torsion angle [130.0 (7)° in (Ia) and 161.6 (2)° in (II)]. The resulting slight conformational differences are reflected in a number of intramolecular contacts being observed in (II) but not in (Ia). Regarding intermolecular interactions, both forms share a similar N-H···O synthon but with differing hydrogen-bonding strength, leading in both cases to C(6) catemers with different chain motifs. There are marked differences between the two forms regarding colour and the (de)localization of a double bond, which allows speculation about the possible existence of different variants of this type of molecule.

(E)-Ethyl 3-(3,4-dihydroxyphenyl)prop-2-enoate: a natural polymorph extracted from Aristotelia chilensis (Maqui).

The natural title compound, C11H12O4, extracted from the Chilean native tree Aristotelia chilensis (Maqui), is a polymorph of the synthetic E form reported by Xia, Hu & Rao [Acta Cryst. (2004), E60, o913-o914]. Both rotational conformers are identical from a metrical point of view, and only differ in the orientation of the 3,4-dihydroxyphenyl ring with respect to the rest of the molecule, which leads to completely different crystal structure arrangements and packing efficiencies. The reasons behind both reside in the different hydrogen-bonding interactions.

3,5-Dimethyl-4-[(E)-(2-nitrophenyl)diazenyl]-1-(2,3,4,5,6-pentafluorophenyl)-1H-pyrazole.

The title compound, C(17)H(10)F(5)N(5)O(2), is described and compared with its 4-nitrophenyl isomer [Bustos, Sánchez, Schott, Alvarez-Thon & Fuentealba (2007). Acta Cryst. E63, o1138-o1139]. The title molecule presents its nitro group split into two rotationally disordered components, which in conjunction with the rotation of the `unclamped' rings constitute the main molecular differences. Packing is directed by a head-to-tail type `I' C-F...F-C interaction, generating double-chain strips running along [100]. These substructures are interlinked by a variety of weak F...F, O...F, F...π and O...π interactions.

Dimers linked by type-I C-F···F-C contacts in (Z)-3-methyl-4-[2-(4-methylphenyl)hydrazinylidene]-1-(pentafluorophenyl)-1H-pyrazol-5(4H)-one.

The title compound, C17H11F5N4O, is described and compared with two closely related analogues in the literature. There are two independent molecules in the asymmetric unit, linked by N-H···O hydrogen bonds and π-π interactions into dimeric entities, presenting a noticeable noncrystallographic C2 symmetry. These dimers are in turn linked by a medium-strength type-I C-F···F-C interaction into elongated tetramers. Much weaker C-H···F contacts link the tetramers into broad two-dimensional substructures parallel to (101).