An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The ligand L1 forms a dinuclear double helicate with Cu+ but upon addition of Ba2+ to the system a side-by-side species is formed both in solution and in the solid state; in the presence of Na+ both the helicate and the side-by-side species are formed in roughly equal amounts in solution.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Two new types of coordination cage have been prepared and structurally characterized: [M16(mu-L1)24]X32 are based on a tetra-capped truncated tetrahedral core and have a bridging ligand L1 along each of the 24 edges; [M12(mu-L1)12(mu3-L2)4]X24 are based on a cuboctahedral core which is supported by a combination of face-capping ligands L2 and edge-bridging ligands L1. The difference between the two illustrates how combinations of ligands with different coordination modes can generate coordination cages which are not available using one ligand type on its own.

Reaction of the bis-bidentate bridging ligand L1 with Co(ClO4)2 or Zn(BF4)2 affords a mixture of complexes [M8(L1)12]X16 and [M6(L1)9]X12 having the same metal : ligand ratio: the former is a molecular cube with a metal ion at each vertex and a bridging ligand spanning each edge, whereas the latter has a metal framework like that of an 'open book' containing cross-linked double helical metal-ligand subunits.

Beta-sultams are the sulfonyl analogues of beta-lactams, and N-acyl beta-sultams are novel inactivators of the class C beta-lactamase of Enterobacter cloacae P99. They sulfonylate the active site serine residue to form a sulfonate ester which subsequently undergoes C-O bond fission and formation of a dehydroalanine residue by elimination of the sulfonate anion as shown by electrospray ionization mass spectroscopy. The analogous N-acyl beta-lactams are substrates for beta-lactamase and undergo enzyme-catalyzed hydrolysis presumably by the normal acylation-deacylation process. The rates of acylation of the enzyme by the beta-lactams, measured by the second-order rate constant for hydrolysis, kcat/K(m), and those of sulfonylation by the beta-sultams, measured by the second-order rate constant for inactivation, k(i), both show a similar pH dependence to that exhibited by the beta-lactamase-catalyzed hydrolysis of beta-lactam antibiotics. Electron-withdrawing groups in the aryl residue of the leaving group of N-aroyl beta-lactams increase the rate of alkaline hydrolysis and give a Bronsted beta(lg) of -0.55, indicative of a late transition state for rate-limiting formation of the tetrahedral intermediate. Interestingly, the corresponding Bronsted beta(lg) for the beta-lactamase-catalyzed hydrolysis of the same substrates is -0.06, indicative of an earlier transition state for the enzyme-catalyzed reaction. By contrast, although the Bronsted beta(lg) for the alkaline hydrolysis of N-aroyl beta-sultams is -0.73, similar to that for the beta-lactams, that for the sulfonylation of beta-lactamase by these compounds is -1.46, compatible with significant amide anion expulsion/S-N fission in the transition state. In this case, the enzyme reaction displays a later transition state compared with hydroxide-ion-catalyzed hydrolysis of the beta-sultam.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

beta-Sultams are the sulfonyl analogues of beta-lactams, and 3-oxo-beta-sultams are both beta-lactams and beta-sultams and, therefore, susceptible to nucleophilic attack at either the acyl or the sulfonyl center. They are novel inactivators of serine enzymes. The second-order rate constant for the inactivation of elastase at pH 6 by N-benzyl-4,4-dimethyl-3-oxo-beta-sultam is 768 M-1 s-1, which is 103-fold greater than that with N-benzoyl beta-sultam. However, in contrast to N-acyl beta-sultams, which sulfonylate the active site serine residue to form a sulfonate ester, 3-oxo-beta-sultams inhibit the enzyme by acylation followed by slow deacylation to regenerate the active enzyme.

Lactobacillus delbrueckii subsp. bulgaricus NCFB2074 when grown in skimmed milk secretes a highly branched exopolysaccharide. The exopolysaccharide has a heptasaccharide repeat unit and is composed of glucose and galactose in the molar ratio 3:4. Using chemical techniques and 1D and 2D NMR spectroscopy the polysaccharide has been shown to possess the following repeat unit structure:

Reaction of the potentially tetradentate N-donor ligand 6,6'-bis(4-methylthiazol-2-yl)-2,2'-bipyridine (L-1) with the transition metal dications Co-II, Ni-II, Cu-II, Cd-II, and Hg-II results in the formation of mononuclear [M(L-1)](2+) complexes, in which a planar ligand coordinates to the metals via all four N-donors. In contrast, reaction of L-1 with Cu-1 and Ag-1 monocations, affords dinuclear double stranded helicate species [M-2(L-1)(2)](2+) (where M = Cu-1 or Ag-1), in which partitioning of the ligand into two bis-bidentate pyridyl-thiazole chelating units allows each ligand to bridge both metal centres. X-Ray crystallography, electrospray mass spectroscopy and NMR spectroscopy reveal that the complexes [M-n(L-1)(m)](2+) (where n = 1, m = 1 and z = 2, when M = Co-II, Ni-II, Cu-II, Cd-II and Hg-II; n = 2, m = 2 and z = 2, when M = Cu-1), retain their solid-state structures in solution. Conversely, whilst H-1 NMR studies suggest that combination of equimolar amounts of Ag(X) (where X = OTf-, BF4- or NO3-) and L-1 (in either nitromethane or acetonitrile) results in the formation of a helicate in solution, in the solid-state, an anion-templating effect gives rise to either mononuclear or dinuclear helicate structures [Ag-n(L-1)(n)][X](n) (where n = 2 when X = OTf-; n = 1 when X = BF4- or NO3-). (c) 2005 Elsevier B.V. All rights reserved.