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PubMed2005

Overlapping resonances in the coherent control of radiationless transitions: internal conversion in pyrazine.

Coherent control of radiationless transitions is developed and applied to internal conversion. Conditions for active versus passive control are described and overlapping resonances are shown necessary for the phase control of radiationless transitions in molecular systems. Applications to pyrazine show the possibility of extensive control via optimized state preparation, as well as the significant role of overlapping resonances, even in the evolution of single vibrational states in S2.

Journal Article↗
PubMed2006

Femtosecond laser pulse control of multidimensional vibrational dynamics: Computational studies on the pyrazine molecule.

The multiconfiguration time-dependent Hartree (MCTDH) method is combined with the optimal control theory (OCT) to study femtosecond laser pulse control of multidimensional vibrational dynamics. Simulations are presented for the widely discussed three-electronic-level vibronic coupling model of pyrazine either in a three or four vibrational coordinate version. Thus, for the first time OCT is applied to a four-coordinate system. Different control tasks are investigated and also some general aspects of the OCT-MCTDH method combination are analyzed.

Journal Article↗
PubMed2000

Pyrazine-2,3-dicarboxamide

In the crystal structure of the title diamide, C(6)H(6)N(4)O(2), linear tapes of carboxamide N-H.O and pyrazine C-H.N hydrogen-bond dimers are connected by N-H.O bonds to form a staircase-like pattern.

Journal Article↗
PubMed2001

2:1 complexes of 2-chloro-4-nitrobenzoic acid and 2-chloro-5-nitrobenzoic acid with pyrazine.

2-chloro-4-nitrobenzoic acid and 2-chloro-5-nitrobenzoic acid form O--H...N hydrogen bonds with pyrazine to afford 2:1 complexes of 2C7H4ClNO4*C4H4N2, (I) and (II), respectively, that are located on inversion centers. The 2C7H4ClNO4*C4H4N2 units in both complexes are connected by weak C--H...O hydrogen bonds; the units build a three-dimensional hydrogen-bond network in (I) and a ribbon structure in (II).

Journal Article↗
PubMed2001

A new packing variant of catena-poly[[aquachlorocopper(II)]-mu-pyrazine-2-carboxylato-O,N:N'].

Single crystals of the title coordination polymer, [CuCl(C5H3N2O2)(H2O)], have been prepared by hydrothermal synthesis. The compound is composed of infinite one-dimensional chains of pseudo-square-pyramidal Cu(II) ions connected via pyrazine-2-carboxylate ligands. A network of O-H...O hydrogen bonding between adjacent chains is responsible for a bilayer structure different from the previously reported polymorph.

Journal Article↗
PubMed2002

catena-Poly[diaquabis(5-chloropyridinium-2-olato-kappaO)copper(II)]-mu-pyrazine-kappa2N:N'] diperchlorate].

In the title compound, [Cu(C(5)H(4)ClNO)(2)(C(4)H(4)N(2))(H(2)O)(2)](ClO(4))(2), the Cu atom, which lies on an inversion centre, has an octahedral environment. The pyrazine ligand also lies about an inversion centre and links adjacent Cu atoms into a chain running along the b axis; perchlorate anions occupy the space between the chains, and the chains use the coordinated water molecules to link to the anions, resulting in a hydrogen-bonded ribbon structure. The donor 5-chloro-2-hydroxypyridine ligand exists in the zwitterionic form, i.e. 5-chloropyridinium-2-olate.

Journal Article↗
PubMed2004

Two triclinic polymorphs of 2,3,5,6-tetrakis(naphthalen-2-ylsulfanylmethyl)pyrazine.

The title compound, C(48)H(36)N(2)S(4), can be crystallized as two polymorphic structures, (I) and (II), both of which are in the triclinic space group P-1 and possess C(i) symmetry. In the crystal structure of polymorph (I), the adjacent naphthalene moieties are orientated towards one another and are inclined to one another by 78.7 (1) degrees, resulting in weak C-H.pi interactions. In polymorph (II), the adjacent substituents are orientated away from one another, enclosing the pyrazine N atoms. In this way, the S atom of one substituent sits below the plane of the naphthalene ring of the other substituent.

Journal Article↗
PubMed1989

Complete amino acid sequence of pyrazine-binding protein from cow nasal mucosa.

The sequence is reported of the pyrazine-binding protein from cow olfactory/respiratory mucosa. The protein consists of 159 amino acids and clearly belongs to the retinol-binding protein family. It is most closely related to the urinary proteins from mice and rats and to the odour-binding protein from rat nasal epithelium. It is unique however, in that only one of the otherwise conserved features of the family is still present--namely a single tryptophan. Most surprisingly the protein contains no cysteine and, therefore, does not rely for its structural stability on the disulphide bond(s) present in other members of this group. A model for the protein has been constructed based on the co-ordinates of beta-lactoglobulin. From this, it is possible to identify residues which may line the binding site. The impression gained is of a much larger pocket than occurs with retinol-binding protein or beta-lactoglobulin. The character of the binding pocket remains essentially hydrophobic but with a significant reduction in its aromatic content and an increase in H-bonding side chains.

Amino Acid Sequence↗
PubMed2004

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitors IV. A series of new derivatives containing a spiro[5H-oxazolo[3,2-a]pyrazine-2(3H),4'-piperidin]-5-one skeleton.

In the course of development of factor Xa (FXa) inhibitor in an investigation involving the synthesis of 1-arylsulfonyl-3-piperazinone derivatives, we found new compounds containing a unique spiro skeleton. Among such compounds, (-)-7-[(6-chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(methoxymethyl)-1'-(4-pyridinyl)-spiro[5H-oxazolo[3,2-a]pyrazine-2(3H),4'-piperidin]-5-one (28, M55529) had activity more favorable than those of previously reported compounds. The inhibitory activity of M55529 for FXa is IC(50)=2 nM, with high selectivity for FXa over thrombin and trypsin.

Crystallography, X-Ray↗
PubMed2000

Antibacterial cobalt(II) and zinc(II) complexes of pyrazine-derived NNO and NNN donor Schiff-bases.

A series of biologically active pyrazine-derived Schiff-base ligands have been synthesized by the condensation reaction of 2-aminopyrazine with salicylaldehyde and acetamidobenzylaldehyde. Then their cobalt(II), nickel(II) and zinc (II) complexes have been prepared. The biological evaluation of the simple uncomplexed ligand in comparison to their complexed compounds have been determined against bacterial strains e.g., Escherichia coil, Staphylococcus aureous and Pseudomonas aeruginosa.

Journal Article↗
PubMed1990

Computer-automated structure evaluation of gastric antiulcer compounds: study of cytoprotective and antisecretory imidazo[1,2-a]pyridines and -pyrazines.

A quantitative structure-activity relationship study of a set of antiulcer compounds has been performed using the computer-automated structure evaluation methodology. Computer-automated structure evaluation identified cyanomethyl and hydroxymethyl functionalities, substituted in the 3-position of imidazo[1,2-a]pyridine and -Pyrazine, as descriptors relevant to antisecretory activity. The phenoxy group at the 8-position and the methyl group at the 2-position were shown to be sterically involved in the activity. A parabolic relationship was observed between the antisecretory activity and the logarithm of the partition coefficient of the compounds. Thus, hydrophobicity is found to be a necessary criterion for the inhibition of acid secretion. An attempt has been made to provide a rationale for designing a more potent antiulcer agent in this series of congeneric compounds.

Animals↗
PubMed1983

[Heterocyclics fused to pyrazine-1,4-dioxide. 3. Synthesis and antibacterial effect of substituted pteridine--5,8-dioxides].

The synthesis of substituted pteridine-5,8-dioxides (6) via reaction of furoxanes (5) with enolizing carbonyl compounds is described. Compounds 5 are obtained either through reaction of chloro pyrimidines 1 with sodium azide, or through diazotization of hydrazino pyrimidine 2 and subsequent thermal decomposition of 3 or through nucleophilic displacement of methoxy against amino groups in 5. The antibacterial activity of the compounds 6a and 6c is directed against some gramnegative organisms, i.e. E. coli, Klebsiella spp. and Proteus spp., with MIC values and ED50 values which do not exceed those of the corresponding pyridol [2,3-b]pyrazine-1,4-dioxides.

Animals↗