Crystallization-induced diastereomer transformation assists the diastereoselective synthesis of 4-nitroisoxazolidine scaffolds.

This communication describes a solution to the vexing problem of synthesis of 4-nitroisoxazolidine rings from cyclic nitrones and β-nitrostyrenes. The adduct 2 is quantitatively synthesised from -β-nitrostyrene under mild conditions avoiding purification, while the adduct 4 is obtained at higher temperatures. Furthermore, a Crystallization-Induced Diastereomer Transformation (CIDT) process was used to epimerise the NO bond from 2 to the adduct 3 with total conversion assisted by the -halogen substitution of the aromatic ring without any additives.

5-Chloro-8-nitro-1-naphthoyl (NNap): A Selective Protective Group for Amines and Amino Acids.

The synthesis of 5-chloro-8-nitro-1-naphthoyl chloride and its use as a protective group for amines is described. Protection is carried out with an auxiliary amine or under mild Schotten-Baumann conditions in high yield (>86%), while deprotection can be achieved easily under gentle reducing conditions due to the large steric tension between C-1 and C-8 naphthalene substituents. The reaction has been successfully tested in dipeptide synthesis and amino alcohols protection, and it has proved selective for the ε-amine group of lysine.

Tryptophan association in water driven by charge-transfer interactions with electron-deficient aromatic haptens.

The ability of a series of electron-deficient aromatic compounds to form charge-transfer complexes with tryptophan in water has been evaluated by X-ray diffraction studies, UV-vis spectra and NMR. As dinitrophenyl (DNP) ligands are well-known to generate antibody-mediated responses and the π-π stacking interactions with tryptophan residues of the antibody Fab fragment have been reported, most of the aromatic receptors studied here are nitro derivatives. Charge-transfer interactions between the rich indole ring of tryptophan and the electron-deficient aromatic receptors have been observed in the solid state, as four crystal structures of the complexes were obtained.

Transesterification of Non-Activated Esters Promoted by Small Molecules Mimicking the Active Site of Hydrolases.

The synthesis of small molecules able to mimic the active site of hydrolytic enzymes has been largely pursued in recent decades. The high reaction rates and specificity shown by natural hydrolases present an attractive target, and yet the preparation of suitable small-molecule mimics remains challenging, requiring activated substrates to achieve productive outcomes. Here we present small synthetic artificial enzymes which mimic the catalytic site and the oxyanion hole of chymotrypsin and N-terminal hydrolases and are able to perform, for the first time, the transesterification of a non-activated ester such as ethyl acetate with methanol under mild and neutral reaction conditions.

An Adjustable Cleft Based on an 8-Sulfonamide-2-Naphthoic Acid with Oxyanion Hole Geometry.

Cleft type receptors showing the oxyanion hole motif have been prepared in a straightforward synthesis starting from the commercial 3,7-dihidroxy-2-naphthoic acid. The double H-bond donor pattern is achieved by the introduction of a sulfonamide group in the C-8 position of naphthalene and a carboxamide at the C-2 position. This cleft, for which the geometry resembles that of an oxyanion hole, is able to adjust to different guests, as shown by the analysis of the X-ray crystal structures of associates with methanol or acetic acid.

Highly Enantioselective Extraction of Phenylglycine by a Chiral Macrocyclic Receptor Based on Supramolecular Interactions.

Using supramolecular interactions, a novel macrocyclic receptor is able to selectively extract zwitterionic phenylglycine from neutral aqueous solutions into chloroform with up to 91.8% . Modeling studies, nuclear magnetic resonance experiments, and X-ray diffraction analysis were carried out to explain the high enantioselectivity observed.

Diastereoselective synthesis of chiral 1,3-cyclohexadienals.

A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a Jørgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potential photoprotective chiral 1,3-cyclohexadienals and extra extended conjugation compounds in a simple manner.

Crystal structure of methyl (4)-4-(4-meth-oxy-benzo-yl)-4-{[(1)-1-phenyl-eth-yl]carbamo-yl}butano-ate.

The title compound, CHNO, was prepared by CAN [cerium(IV) ammonium nitrate] oxidation of the corresponding β-lactam. The dihedral angle between the benzene rings is 13.3 (4)° and the C-N-C(=O)-C torsion angle is 176.

Crystal structure of (2*,3a*)-2-phenyl-sulfonyl-2,3,3a,4,5,6-hexa-hydro-pyrrolo-[1,2-]isoxazole.

The title compound, CHNOS, was prepared by 1,3-dipolar cyclo-addition of 3,4-di-hydro-2-pyrrole 1-oxide and phenyl vinyl sulfone. In the mol-ecule, both fused five-membered rings display a twisted conformation. In the crystal, C-H⋯O hydrogen bonds link neighbouring mol-ecules, forming chains running parallel to the axis.

A molecular receptor selective for zwitterionic alanine.

A molecular receptor has been synthesized joining an aza-crown ether with a chiral chromane which mimics the oxyanion hole of the enzymes. With this receptor an apolar host-guest complex with zwitterionic alanine has been achieved through the formation of up to seven H-bonds. This complex allows the extraction of aqueous alanine to a chloroform phase, while other natural amino acids are poorly extracted or are not extracted at all.

A bio-inspired enantioselective small-molecule artificial receptor for β adrenergic agonists and antagonists and its application for enantioselective extraction.

Administration of enantiomerically pure β-adrenergic agonists and antagonists increases their activity and reduces side effects. We report here a small-molecule artificial receptor (SMAR) that, by mimicking the β-adrenergic receptor, is able to enantioselectively extract commercial β-adrenergic interacting drugs. The selectivity is justified according to DFT calculations and X-ray diffraction experiments.

A highly selective receptor for zwitterionic proline.

A chiral chromane receptor has been synthesized which mimics the oxyanion hole of the enzymes. In this receptor H-bonds and cation-π interactions team up to generate an apolar host-guest complex with zwitterionic proline. This complex allows the extraction of only proline to a chloroform phase, while no other natural amino acids are extracted.

Enantioselective synthesis of cis-decalins using organocatalysis and sulfonyl Nazarov reagents.

The first organocatalytic synthesis of cis-decalins using sulfonyl Nazarov reagents is reported. The Jørgensen's catalyst directs this highly enantioselective synthesis using different cyclohexenal derivatives.

Chiral recognition with a benzofuran receptor that mimics an oxyanion hole.

A new chiral benzofuran receptor has been synthesized and its properties in the association of amino acid derivatives have been studied. X-ray structures were obtained and these corroborate the presence of an oxyanion-hole motif in these structures.

Usefulness of endoluminal catheter colonization surveillance cultures to reduce catheter-related bloodstream infections in hemodialysis.

Background: To evaluate the use of surveillance cultures (SCs) to prevent catheter-related bloodstream infections (CRBSIs) in asymptomatic hemodialysis (HD) patients.

Methods: In 2011-2012, we conducted a prospective study of HD patients with tunneled cuffed central venous catheters (TCCs). Colonization of the catheter lumen was assessed every 15 days by inoculating ~5 mL endoluminal blood into aerobic culture bottles.

Relationship between agr dysfunction and reduced vancomycin susceptibility in methicillin-susceptible Staphylococcus aureus causing bacteraemia.

Objectives: Limited data exist regarding the role of agr dysfunction in reducing susceptibility to vancomycin in methicillin-susceptible Staphylococcus aureus (MSSA). This study investigated the clinical and molecular epidemiology of MSSA causing bacteraemia, with emphasis on the reduced susceptibility to vancomycin (RSV) phenotype (MIC ≥ 1.5 mg/L) and its relationship with agr dysfunction.

Mn(II) complexes with sulfonamides as ligands. DNA interaction studies and nuclease activity.

Sulfonamides derived from 8-aminoquinoline react with Mn(II) and Mn(III) salts to form Mn(II) complexes; the Mn(III) species are reduced to the divalent state in the presence of 1,10 phenanthroline and bipyridine. Their molecular structure, determined by single crystal X-ray diffraction, show that all the complexes present a distorted octahedral geometry, in which the deprotonated sulfonamide acts as a bidentate ligand. UV-visible spectroscopy and changes in the melting temperature (Tm) of calf thymus DNA show a strong interaction of these complexes with DNA.

(2R,3S,4R)-3,4-Isopropyl-idenedi-oxy-2-(phenyl-sulfonyl-meth-yl)pyrrolidin-1-ol.

The title compound, C(14)H(19)NO(5)S, was prepared by nucleophilic addition of the lithium derivative of methyl-phenyl-sulfone to (3S,4R)-3,4-isopropyl-idene-dioxy-pyrroline 1-oxide. There are four mol-ecules in the asymmetric unit. The crystal structure determination confirms the configuration of the chiral centres as 2R,3S,4R.

VIM-2-producing multidrug-resistant Pseudomonas aeruginosa ST175 clone, Spain.

A total of 183 patients were colonized or infected with multidrug-resistant Pseudomonas aeruginosa isolates at a hospital in Spain during 2007-2010; prevalence increased over this period from 2.8% to 15.3%.

Long-term evolution of multiple outbreaks of Serratia marcescens bacteremia in a neonatal intensive care unit.

The annual incidence of Serratia marcescens bacteremia in a neonatal intensive care unit increased significantly between 2002 and 2010. Molecular epidemiology studies revealed that 8 clones were responsible for 85.2% of cases.

4,5-Dibromo-2,7-di-tert-butyl-9,9-dimethyl-9H-thioxanthene.

In the title compound, C(23)H(28)Br(2)S, the thioxanthene unit is twisted, showing a dihedral angle of 29.3 (5)° between the benzene rings. When projected along [001], the packing shows two types of channels.

(3S*,4S*,E)-tert-Butyl 3,4-dibromo-5-oxo-cyclo-oct-1-ene-carboxyl-ate.

The title compound, C(13)H(18)Br(2)O(3), was prepared by a bromination reaction of (1E,3Z)-methyl 5-oxocyclo-octa-1,3-diene-carboxyl-ate, which was obtained by an ep-oxy-dation reaction of tert-butyl cyclo-oct-1,3-diene-carboxyl-ate. The crystal structure confirms unequivocally the absolute configuration of both chiral centres to be S. In the crystal, C-H⋯O inter-actions link the mol-ecules into chains running along the c axis.

Bis-amidocarbazolyl urea receptor for short-chain dicarboxylate anions.

Urea receptor 1 based on two (1-amino-8-amido-3,6-dichloro)carbazole units shows a strong association with dicarboxylate anions such as oxalate, malonate and succinate guests through multiple hydrogen bonds from the carbazole, urea and amide NH groups. (1)H NMR complexation studies exhibit high values of association constants in DMSO-d(6). X-ray structures of the 1 : 1 complexes of 1 with oxalate and malonate as their ditetrabutylammonium salts were obtained.

Sulfonamide carbazole receptors for anion recognition.

Carbazole-based receptors functionalized with two sulfonamide groups have been synthesized and their properties as anion receptors have been evaluated. The receptor with bis(trifluoromethyl)aniline groups has shown a very high affinity for halide ions, especially remarkable as only two hydrogen bonds are formed in the complexes. (1)H NMR and fluorescence titrations have been carried out and binding constants up to 7.