RESUMO
The uncatalysed cycloaddition of substituted diaryldiazo compounds onto bicyclic unsaturated lactams derived from pyroglutamic acid efficiently leads to highly functionalised azatricyclononanes. The products are readily elaborated to deprotected pyroglutamate derivatives, providing rapid access to conformationally constrained amino acids and their analogues. Preliminary assessment of antibacterial activity against one Gram positive and one Gram negative organism indicated high levels of efficacy in some cases.
Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Lactamas/química , Antibacterianos/síntese química , Catálise , Técnicas de Química Sintética , Cristalografia por Raios X , Reação de Cicloadição , Ciclopropanos/química , Avaliação Pré-Clínica de Medicamentos/métodos , Escherichia coli/efeitos dos fármacos , Espectroscopia de Ressonância Magnética , Conformação Molecular , Prolina/química , Ácido Pirrolidonocarboxílico/química , Staphylococcus aureus/efeitos dos fármacosRESUMO
The title compound, [Ni(C13H11N4S2)2], was obtained by the reaction of S-2-picolyldi-thio-carbazate and pyridine-2-carbaldehyde with nickel(II) acetate. The Ni(II) atom is located on a twofold rotation axis and is bonded to four N atoms at distances of 2.037â (8) and 2.109â (9)â Å, and to two S atoms at a distance of 2.406â (3)â Å, leading to a distorted octa-hedral coordination. The angle between the mean planes of the coordinating moieties of the two symmetry-related tridentate ligands is 83.3â (2)°. In the crystal, complex mol-ecules are linked by weak C-Hâ¯S hydrogen bonds, π-π inter-actions between the pyridine rings [centroid-centroid distance = 3.775â (9)â Å] and C-Hâ¯π inter-actions. The hydrogen-bonding inter-actions lead to the formation of layers parallel to (010); π-π inter-actions link these layers into a three-dimensional network.
RESUMO
The synthesis and likely conformational structure of rigid spirocyclic bislactams and lactam-lactones derived from pyroglutamic acid, and their suitability as lead structures for applications in drug development programmes using cheminformatic analysis, has been investgated.
Assuntos
Ácido Pirrolidonocarboxílico/química , Compostos de Espiro/síntese química , Ciclização , Lactamas/síntese química , Lactonas/síntese química , Modelos Moleculares , Estrutura MolecularRESUMO
X-ray crystallographic analysis with Cu Kα radiation established the relative configurations of the stereogenic centers in the title compound, C(15)H(20)N(2)O(5), and clarified mechanistic ambiguities in the synthesis. The conformation of the five-membered ring approximates twisted, about a C-O bond. The absolute configuration of this carbon-branched dipeptide isostere was known based on the use of d-ribose as the starting material. Refinement of the Flack parameter gave an ambiguous result but the refined Hooft parameter is in agreement with the assumed (d-ribose) absolute structure. The crystal structure consists of N-Hâ¯O and O-Hâ¯O hydrogen-bonded bi-layers, with the terminal methyl and phenyl groups forming a hydro-phobic inter-layer inter-face. Some weak C-Hâ¯O inter-actions are also present.
RESUMO
A rhodium(I) catalyst incorporating the Me-DuPhos ligand promotes enantioselective intermolecular hydroacylation between beta-S-aldehydes and 1,3-disubstituted allenes. The nonconjugated enone products are obtained in good yields and with high enantioselectivities.
Assuntos
Aldeídos/química , Alcenos/química , Química/métodos , Ródio/química , Carbono/química , Catálise , Ligantes , Metais/química , Modelos Químicos , Estrutura Molecular , Estereoisomerismo , TemperaturaRESUMO
In situ resolution of the rapidly racemising diphosphine BIPHEP and its relatives with the cationic Rh complex of (S,S)-bicyclonona-2,6-diene permits the asymmetric hydrogenation of dehydroamino esters.
RESUMO
3alpha,12alpha-dihydroxy-5beta-cholan-24-oic acid (deoxycholic acid DCA) is able to discriminate between the R- and S-enantiomers of camphorquinone and endo-(+)-3-bromocamphor and select only the S-enantiomers from a racemic mixture. DCA forms novel well ordered 1:1 adducts with (1S)-(+)-camphorquinone and (1S)-endo-(-)-3-bromocamphor, both of which have been characterized by single crystal X-ray diffraction (SXRD). When DCA is cocrystallized with (RS)-camphorquinone and (RS)-endo-3-bromocamphor, 1:1 adducts of the S-enantiomers are produced together with crystals of the free racemic guest. In contrast, in the absence of (1S)-(+)-camphorquinone, DCA forms a 2:1 adduct with (1R)-(-)-camphorquinone. In this 2:1 adduct the guest is disordered at ambient temperature and undergoes a phase change in the region 160-130 K similar to that observed for the ferrocene adduct, but with only partial ordering of the guest. The SXRD structure of the low temperature form and the variable temperature (13)C CP/MAS NMR are reported. Cocrystallizing DCA with (1R)-endo-(+)-3-bromocamphor gives the free guest and a glassy solid.
RESUMO
The title compound, C(21)H(26)O(10)S, was synthesized in a single step from mannose penta-acetate. The mol-ecular structure confirms the α configuration of the anomeric thioaryl substituent. Spectroscopic and melting-point data obtained for the title compound are in disagreement with those previously reported, indicating the previously reported synthesis [Durette & Shen (1980 â¶). Carbohydr. Res. 81, 261-274] to be erroneous. The crystal structure is stabilized by weak inter-molecular C-Hâ¯O hydrogen bonds.
RESUMO
The synthesis and characterization of the monomeric, two-coordinate transition-metal complexes (2,6-Mes(2)C(6)H(3))(2)M (Mes = mesityl, 2,4,6-Me(3)C(6)H(2), M = Mn, Fe, Co) are reported; (2,6-Mes(2)C(6)H(3))(2)Co is the first structurally authenticated two-coordinate, homoleptic cobalt(II) complex featuring sigma-bonded aryl ligands.
RESUMO
Novel permethylated pentalenide anions are reported which offer exciting new opportunities for the future development of organometallic pentalene chemistry.
RESUMO
Diiron complexes of fluorene and fluorene* (1,2,3,4,5,6,7,8,9-nonamethylfluorene) have been found to be catalysts for the dechlorination of chlorinated aromatics, such as PCBs.
Assuntos
Cloro/química , Hidrocarbonetos Clorados/química , Bifenilos Policlorados/química , Catálise , Cristalografia por Raios X , Estrutura MolecularRESUMO
The title compound, C(40)H(31)NO(11)S·0.53CH(2)Cl(2)·0.38C(4)H(10)O, was synthesized in two steps from mannose penta-acetate and single crystals were grown by slow evaporation. The structure was determined by single-crystal X-ray diffraction, confirming the α-configuration of the anomeric thioaryl substituent. The asymmetric unit contains two crystallographically distinct mol-ecules of the carbohydrate. The central pyran-ose rings of these are geometrically similar, but there are differences in the orientations of the benzoate substituents.
RESUMO
The Kiliani reaction on 1-de-oxy-(N,N-dimethyl-amino)-d-fructose, itself readily available from reaction of dimethyl-amine and d-glucose, proceeded to give access to the title ß-sugar amino acid, C(15)H(27)NO(7). X-ray crystallography determined the stereochemistry at the newly formed chiral center. There are two mol-ecules in the asymmetric unit; they are related by a pseudo-twofold rotation axis and have very similar geometries, differing only in the conformation of one of the acetonide rings. All the acetonide rings adopt envelope conformations; the flap atom is oxygen in three of the rings, but carbon in one of them. There are two strong hydrogen bonds between the two independent mol-ecules, and further weak hydrogen bonds link the mol-ecules to form infinite chains running parallel to the a axis.
RESUMO
The interweaving of two identical acyclic positively charged anion recognizing units around a chloride anion template leads to the formation of an orthogonal supramolecular ensemble which upon subsequent double ring cyclization gives a chloride selective [2]catenane in very high yield.
Assuntos
Catenanos/química , Cloretos/química , Ânions/química , Ciclização , Ligação de Hidrogênio , Espectroscopia de Ressonância Magnética/métodos , Modelos Moleculares , Estrutura Molecular , Sensibilidade e EspecificidadeRESUMO
A novel heteroditopic calix[4]diquinone receptor capable of binding an anion and cation simultaneously in a cooperative fashion is shown only to recognise halide anions in the presence of a suitable cobound cationic guest species, and displays affinity for certain ion-pairs where no affinity for either of the free ions is observed.
Assuntos
Calixarenos/química , Compostos Heterocíclicos/química , Ionóforos/química , Quinonas/química , Acetonitrilas/química , Ânions/química , Sítios de Ligação , Calixarenos/metabolismo , Cátions/química , Cloretos/química , Compostos Heterocíclicos/metabolismo , Ionóforos/metabolismo , Cinética , Espectroscopia de Ressonância Magnética , Modelos Químicos , Modelos Moleculares , Prótons , Quinonas/metabolismoRESUMO
Reaction of the dimeric zirconium imido compound [Zr2(mu-NAr)2Cl4(THF)4] with tris(3,5-dimethylpyrazolyl)methyl silane very selectively gave [Zr{(Me2pz)2Si(Me)NAr}Cl3] (1), a highly active pre-catalyst for ethylene polymerisation; a more general and versatile route to N3 donor heteroscorpionate compounds was achieved via the protio ligand (Me2pz)2CHSi(Me)2N(H)iPr for which neutral and cationic organometallic Group 3 and 4 derivatives are reported (Ar = 2,6-C6H(3)iPr2).
Assuntos
Imidas/química , Compostos Organometálicos/síntese química , Zircônio/química , Catálise , Cristalografia por Raios X , Etilenos/síntese química , Etilenos/química , Ligantes , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/química , Pirazóis/química , Silanos/química , EstereoisomerismoRESUMO
Ethylene polymerisation productivities of tris(pyrazolyl)methane-supported catalysts [Ti(NR){HC(Me2pz)3}Cl2] show a dramatically different dependence on the imido R-group compared to those of their TACN analogues, attributed to differences in fac-N3 donor topology; when treated with AliBu3, the zwitterionic tris(pyrazolyl)methide compound [Ti(N-2-C6H4tBu){C(Me2pz)3}Cl(THF)] also acts as a highly active, single site catalyst (TACN = 1,4,7-trimethyltriazacyclononane).
Assuntos
Compostos Aza/síntese química , Imidas/química , Compostos Organometálicos/síntese química , Pirazóis/síntese química , Titânio/química , Boratos/química , Catálise , Ligantes , Estrutura Molecular , Polímeros/químicaRESUMO
On treatment with trifluoroacetic acid butenolide 14 undergoes N-Boc deprotection and condensation followed by an iminium ion activated intramolecular Diels-Alder cycloaddition to give the (+)-himbacine precursor 11 on reductive work up. Compound 11 was converted into (+)-himbacine in four synthetic steps. [reaction: see text]
Assuntos
Alcaloides/síntese química , Furanos/síntese química , Naftalenos/síntese química , Piperidinas/síntese química , 4-Butirolactona/análogos & derivados , Aldeídos , Alcenos , Modelos Moleculares , Estereoisomerismo , Ácido TrifluoracéticoRESUMO
As part of our continuing studies of pyrone-containing natural products, a series 6-methoxypyran-2-ones were synthesized. These were found to react with molecular oxygen at 20 degrees C, and this novel reaction yielded a series of highly functionalized alpha,beta-butenolides. [reaction: see text]
RESUMO
[structure: see text] A vinylene-linked porphyrin dimer, with no substituents at the beta-positions, has been synthesized by CuI/CsF promoted Stille coupling. In the crystal structure of this dimer, the C(2)H(2) bridge is twisted by 45 degrees relative to the plane of the porphyrins. The absorption, emission spectra, and electrochemistry reveal substantial porphyrin-porphyrin pi-conjugation. The triplet excited-state absorption spectrum of this dimer makes it suitable for reverse saturable absorption at 710-900 nm.