A structural systematic study of three isomers of difluoro-N-(4-pyridyl)benzamide

The isomers 2,3-, (I), 2,4-, (II), and 2,5-difluoro-N-(4-pyridyl)benzamide, (III), all with formula C₁₂H₈F₂N₂O, all exhibit intramolecular C-H...O=C and N-H...F contacts [both with S(6) motifs]. In (I), intermolecular N-H...O=C interactions form one-dimensional chains along [010] [N...O = 3.0181 (16) Å], with weaker C-H...N interactions linking the chains into sheets parallel to the [001] plane, further linked into pairs via C-H...F contacts about inversion centres; a three-dimensional herring-bone network forms via C-H...π(py) (py is pyridyl) interactions. In (II), weak aromatic C-H...N(py) interactions form one-dimensional zigzag chains along [001]; no other interactions with H...N/O/F < 2.50 Å are present, apart from long N/C-H...O=C and C-H...F contacts. In (III), N-H...N(py) interactions form one-dimensional zigzag chains [as C(6) chains] along [010] augmented by a myriad of weak C-H...π(arene) and O=C...O=C interactions and C-H...O/N/F contacts. Compound (III) is isomorphous with the parent N-(4-pyridyl)benzamide [Noveron, Lah, Del Sesto, Arif, Miller & Stang (2002). J. Am. Chem. Soc. 124, 6613-6625] and the three 2/3/4-fluoro-N-(4-pyridyl)benzamides [Donnelly, Gallagher & Lough (2008). Acta Cryst. C64, o335-o340]. The study expands our series of fluoro(pyridyl)benzamides and augments our understanding of the competition between strong hydrogen-bond formation and weaker influences on crystal packing

A structural systematic study of four isomers of difluoro-N-(3-pyridyl)benzamide

The four isomers 2,4-, (I), 2,5-, (II), 3,4-, (III), and 3,5-difluoro-N-(3-pyridyl)benzamide, (IV), all with formula C12H8F2N2O, display molecular similarity, with interplanar angles between the C6/C5N rings ranging from 2.94 (11)° in (IV) to 4.48 (18)° in (I), although the amide group is twisted from either plane by 18.0 (2)-27.3 (3)°. Compounds (I) and (II) are isostructural but are not isomorphous. Intermolecular N-H...O=C interactions form one-dimensional C(4) chains along [010]. The only other significant interaction is C-H...F. The pyridyl (py) N atom does not participate in hydrogen bonding; the closest H...Npy contact is 2.71 Å in (I) and 2.69 Å in (II). Packing of pairs of one-dimensional chains in a herring-bone fashion occurs via [pi]-stacking interactions. Compounds (III) and (IV) are essentially isomorphous (their a and b unit-cell lengths differ by 9%, due mainly to 3,4-F2 and 3,5-F2 substitution patterns in the arene ring) and are quasi-isostructural. In (III), benzene rotational disorder is present, with the meta F atom occupying both 3- and 5-F positions with site occupancies of 0.809 (4) and 0.191 (4), respectively. The N-H...Npy intermolecular interactions dominate as C(5) chains in tandem with C-H...Npy interactions. C-H...O=C interactions form R22(8) rings about inversion centres, and there are [pi]-[pi] stacks about inversion centres, all combining to form a three-dimensional network. By contrast, (IV) has no strong hydrogen bonds; the N-H...Npy interaction is 0.3 Å longer than in (III). The carbonyl O atom participates only in weak interactions and is surrounded in a square-pyramidal contact geometry with two intramolecular and three intermolecular C-H...O=C interactions. Compounds (III) and (IV) are interesting examples of two isomers with similar unit-cell parameters and gross packing but which display quite different intermolecular interactions at the primary level due to subtle packing differences at the atom/group/ring level arising from differences in the peripheral ring-substitution patterns

Redetermination of para-aminopyridine (fampridine, EL-970) at 150 K

The structure of fampridine (EL-970) or 4-aminopyridine, C₅H₆N₂, has been redetermined at 150 K. The room-temperature structure has been reported previously [Chao & Schempp (1977). Acta Cryst. B33, 1557-1564]. Pyramidalization at the amine N atom occurs in fampridine, with the N atom 0.133 (11) Å from the plane of the three C/H/H atoms to which it is bonded; the interplanar angle between the pyridyl ring and NH2 group is 21 (2)°. Aggregation in the solid state occurs by N-H...N and N-H...[pi](pyridine) interactions with N...N and N...[pi](centroid) distances of 2.9829 (18) and 3.3954 (15) Å, respectively; a C-H...[pi](pyridine) contact completes the intermolecular interactions [C...[pi](centroid) = 3.6360 (16) Å]

The synthesis, structural characterization and biological evaluation of potential chemotherapeutic agents

The design and synthesis of potent chemotherapeutics offers one of the most successful routes for the treatment of disease. A series of amino acid, dipeptidyl and stilbenyl derivatives have been synthesised and evaluated as potential therapeutic agents. These compounds were fully characterised by a range o f spectroscopic techniques including; IR, IH, 13C, 19F, 3 IP, DEPT 135 and HMQC NMR in addition to ESIMS. X-ray crystal structures were also obtained in certain cases. Multidrug resistance (MDR) is used to define resistance whereby cells become resistant to different drugs with no obvious structural resemblance and with different cellular targets. The preparation o f TV-fluorobenzoyl amino acid derivatives has resulted in the synthesis o f multidrug resistance modulators. TV-pentafluorobenzoyl-L-alanine methyl ester 81 was the most potent derivative. This compound although relatively non-toxic was shown to increase the potency o f the anticancer drug epirubicin by 65%. Fasciolosis is not only an important human disease but also affects cattle and sheep worldwide causing economic losses of approx 2 billion dollars. Potent inhibitors of Fasciola hepatica cathepsin L endoproteases have been developed. These dipeptidyl derivatives were synthesised by using the standard 1,3-dicyclohexylcarbodiimide (DCC) or l-ethyl-3-(3- dimethylaminopropyl)carbodiimide (EDC), 1-hydroxybenzotriazole (HOBt) protocol. N-4- fluorobenzoyl-L-leucine-glycine nitrile 151 was shown to be the most active compound with an IC50 value o f 2.78 |j.M recorded. a-Chymotrypsin has served as a prototypical enzyme for the serine proteases and has been very useful as a model target enzyme for the development of compounds of pharmacological interest. A series of dipeptidyl phosphonate esters were prepared by standard EDC/HOBt protocol. jV-4 -fluorobenzenesulphonyl-glycine-phenylalaninep-(OPh) 2 165 was the most potent derivative with an IC50 value o f 16.15 jiM against a-chymotrypsin. Resveratrol found in grapes is a naturally occurring phytoalexin formed in response to fungal infections. It has been shown to exhibit various biological properties including antifungal, anticancer, estrogenic and heart protecting activities. The synthesis of fluorinated analogues of this bioactive compound were carried out using a decarbonylative Heck reaction with preliminary biological results indicating that (£)-l-(4-acetoxystyryl)-3,5- difluorobenzene 192 was a potent growth inhibitor o f breast, lung and central nervous system cancer lines. At a concentration of 100 (.iM the growth of central nervous system cancer waslimited by 99%

Ethyl and isopropyl 4-ferrocenylbenzoate.

The title compounds, [Fe(C5H5)(C14H13O2)] and [Fe(C5H5)- (C15H15O2)], respectively, contain the ferrocenyl 5(C5H4) and phenylene ±C6H4± rings in a nearly coplanar arrangement, with interplanar angles of 6.88 (12) and 10.5 (2), respectively. Molecules of the ethyl ester form dimers through 5(C5H5)CÐ H O C hydrogen bonds, with graph set R22 (20), and, together with Csp3ÐH (C5H5) interactions, generate a one-dimensional column (irregular ladder). Molecules of the isopropyl ester aggregate through 5(C5H5)CÐH (C6H4) interactions

2,3-Difluoro-N-(2-pyrid­yl)benzamide

The title compound, C12H8F2N2O, crystallizes with two independent mol­ecules in the asymmetric unit. The independent mol­ecules differ slightly in conformation; the dihedral angles between the benzene and pyridine rings are 51.58 (5) and 49.97 (4)°. In the crystal structure, mol­ecules aggregate via N—H⋯Npyridine inter­actions as hydrogen-bonded dimers with the structural motif R 2 2(8), and these dimers are linked via C—H⋯O inter­actions to form a supra­molecular chain

Biodiversity on Broadway - Enigmatic Diversity of the Societies of Ants (Formicidae) on the Streets of New York City

Each year, a larger proportion of the Earth's surface is urbanized, and a larger proportion of the people on Earth lives in those urban areas. The everyday nature, however, that humans encounter in cities remains poorly understood. Here, we consider perhaps the most urban green habitat, street medians. We sampled ants from forty-four medians along three boulevards in New York City and examined how median properties affect the abundance and species richness of native and introduced ants found on them. Ant species richness varied among streets and increased with area but was independent of the other median attributes measured. Ant assemblages were highly nested, with three numerically dominant species present at all medians and additional species present at a subset of medians. The most common ant species were the introduced Pavement ant (Tetramorium caespitum) and the native Thief ant (Solenopsis molesta) and Cornfield ant (Lasius neoniger). The common introduced species on the medians responded differently to natural and disturbed elements of medians. Tetramorium caespitum was most abundant in small medians, with the greatest edge/area ratio, particularly if those medians had few trees, whereas Nylanderia flavipes was most abundant in the largest medians, particularly if they had more trees. Many of the species encountered in Manhattan were similar to those found in other large North American cities, such that a relatively small subset of ant species probably represent most of the encounters humans have with ants in North America