Synthesis and crystal structures of two solvates of 1-{[2,6-bis-(hy-droxy-meth-yl)-4-methyl-phen-oxy]meth-yl}-3,5-bis-{[(4,6-di-methyl-pyridin-2-yl)amino]meth-yl}-2,4,6-tri-ethyl-benzene.

In the crystal structures of the formamide monosolvate (1a) and the n-propanol/H2O solvate/hydrate (1b) of the title compound, C38H50N4O3 (1), the tripodal host mol-ecule adopts a conformation in which the substituents attached to the central benzene ring are arranged in an alternating order above and below the ring plane. As a result of the different nature of the involved guest species, the crystal components in 1a create a three-dimensional supra-molecular architecture, while the crystal structure of 1b consists of two-dimensional supra-molecular aggregates extending parallel to the crystallographic ab plane.

N,N'-[1,4-Phenyl-enebis(imino-carbon-yl)]bis-(l-phenyl-alanine) tetra-hydro-furan disolvate.

The title compound, C26H26N4O6·2C4H8O, representing a bis-urea with terminal phenyl-alanine units, crystallized with two tetra-hydro-furan (THF) mol-ecules. The main mol-ecule is located on a crystallographic twofold axis, while the solvent mol-ecule is disordered over two positions, with occupancies of 0.571 (15) and 0.429 (15). The host mol-ecules are linked by N-H⋯O=C hydrogen bonds and C-H⋯O contacts with R 2 1(6) and R 2 1(7) ring motifs. The THF mol-ecules enclosed in the crystal are connected to the bis-urea compound via O-H⋯O and C-H⋯O inter-actions.

Cycloalkyl Groups as Building Blocks of Artificial Carbohydrate Receptors: Studies with Macrocycles Bearing Flexible Side-Arms.

The cyclopentyl group was expected to act as a building block for artificial carbohydrate receptors and to participate in van der Waals contacts with the carbohydrate substrate in a similar way as observed for the pyrrolidine ring of proline in the crystal structures of protein-carbohydrate complexes. Systematic binding studies with a series of 1,3,5-trisubstituted 2,4,6-triethylbenzenes bearing various cycloalkyl groups as recognition units provided indications of the involvement of these groups in the complexation process and showed the influence of the ring size on the receptor efficiency. Representatives of compounds that exhibit a macrocyclic backbone and flexible side arms were now chosen as further model systems to investigate whether the previously observed effects represent a general trend. Binding studies with these macrocycles towards ß-D-glucopyranoside, an all-equatorial substituted carbohydrate substrate, included 1H NMR spectroscopic titrations and microcalorimetric investigations. The performed studies confirmed the previously observed tendency and showed that the compound bearing cyclohexyl groups displays the best binding properties.

Synthesis and crystal structure of 1,3-bis-{[N,N-bis-(2-hy-droxy-eth-yl)amino]-meth-yl}-5-{[(4,6-di-methyl-pyridin-2-yl)amino]-meth-yl}-2,4,6-tri-ethyl-benzene.

In the crystal structure of the title compound, C30H50N4O4, the two bis-(hy-droxy-eth-yl)amino moieties and the 2,4-di-methyl-pyridinyl-amino unit of the mol-ecule are located on one side of the central benzene ring, while the ethyl substituents are oriented in the opposite direction. The dihedral angle between the planes of the aromatic rings is 73.6 (1)°. The conformation of the mol-ecule is stabilized by intra-molecular O-H⋯O (1.86-2.12 Å) and C-H⋯N (2.40, 2.54 Å) hydrogen bonds. Dimers of inversion-related mol-ecules represent the basic supra-molecular entities of the crystal structure. They are further connected via O-H⋯O hydrogen bonding into undulating layers extending parallel to the crystallographic bc plane. Inter-layer inter-action is accomplished by weak C-H⋯π contacts.

Crystal structures of 2-[3,5-bis-(bromo-meth-yl)-2,4,6-tri-ethyl-benz-yl]isoindoline-1,3-dione and 2-{5-(bromo-meth-yl)-3-[(1,3-dioxoisoindolin-2-yl)meth-yl]-2,4,6-tri-ethyl-benz-yl}isoindoline-1,3-dione.

The title compounds, C23H25Br2NO2 (1) and C31H29BrN2O4 (2), crystallize in the space group P21/n with two (1-A and 1-B) and one mol-ecules, respectively, in the asymmetric unit of the cell. The mol-ecular conformation of these compounds is stabilized by intra-molecular C-H⋯O hydrogen bonds and C-H⋯N or C-H⋯π inter-actions. The crystal structure of 1 features a relatively strong Br⋯O=C halogen bond, which is not observed in the case of 2. Both crystal structures are characterized by the presence of C-H⋯Br hydrogen bonds and numerous inter-molecular C-H⋯O hydrogen-bonding inter-actions.

Isolation and characterization of arsenic-binding siderophores from Rhodococcus erythropolis S43: role of heterobactin B and other heterobactin variants.

Rhodococcus erythropolis S43 is an arsenic-tolerant actinobacterium isolated from an arsenic contaminated soil. It has been shown to produce siderophores when exposed to iron-depleting conditions. In this work, strain S43 was shown to have the putative heterobactin production cluster htbABCDEFGHIJ(K). To induce siderophore production, the strain was cultured in iron-depleted medium in presence and absence of sodium arsenite. The metabolites produced by S43 in the colorimetric CAS and As-mCAS assays, respectively, showed iron- and arsenic-binding properties reaching a chelating activity equivalent to 1.6 mM of desferroxamine B in the supernatant of the culture without arsenite. By solid-phase extraction and two subsequent HPLC separations from both cultures, several fractions were obtained, which contained CAS and As-mCAS activity and which were submitted to LC-MS analyses including fragmentation of the major peaks. The mixed-type siderophore heterobactin B occurred in all analyzed fractions, and the mass of the "Carrano heterobactin A" was detected as well. In addition, generation of a molecular network based on fragment spectra revealed the occurrence of several other compounds with heterobactin-like structures, among them a heterobactin B variant with an additional CH2O moiety. 1H NMR analyses obtained for preparations from the first HPLC step showed signals of heterobactin B and of "Carrano heterobactin A" with different relative amounts in all three samples. In summary, our results reveal that in R. erythropolis S43, a pool of heterobactin variants is responsible for the iron- and arsenic-binding activities. KEY POINTS: • Several heterobactin variants are the arsenic-binding compounds in Rhodococcus erythropolis S43. • Heterobactin B and the compound designated heterobactin A by Carrano are of importance. • In addition, other heterobactins with ornithine in the backbone exist, e.g., the new heterobactin C.

Crystal structures of monohydrate and methanol solvate compounds of {1-[(3,5-bis{[(4,6-dimethylpyridin-2-yl)amino]methyl}-2,4,6-triethylbenzyl)amino]cyclopentyl}methanol.

In the title monohydrate compound, 1a, and the methanol solvate compound, 1b, the tri-ethyl-benzene derivative, C35H51N5O, has three functionalized side arms and three ethyl groups, the former being located on one side of the central benzene ring, while the latter are directed to the opposite side. Both the crystals are constructed of structurally similar dimers of 1:1 host-guest complexes held together by N-H⋯O and O-H⋯N hydrogen bonds, and in 1a additionally by O-H⋯O hydrogen bonds. The structure of 1b contains additional highly disordered solvent mol-ecules. Thus, the SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18] in PLATON was used to generate a modified data set, in which the contribution of the disordered mol-ecules to the structure amplitudes is eliminated. These solvent mol-ecules are not considered in the reported chemical formula.

Unique hydrogen-bonded complex of hydronium and hydroxide ions.

H3 O(+) and OH(-) , formed by the self-ionization of two coordinating water molecules during the crystal growing of a host molecule [1,3,5-tris(hydroxymethyl)2,4,6-triethylbenzene (1)], could be effectively stabilized by hydrogen-bonding interactions with the preorganized hydroxy groups of three molecules of 1. The binding motifs observed in the complex (1)3 ⋅H3 O(+) ⋅HO(-) show remarkable similarity to those postulated for the hydrated hydronium and hydroxide ion complexes, which play important roles in various chemical, biological, and atmospheric processes, but their molecular structures are still not fully understood and remain a subject of intensive research.