A simple and efficient PdCl2 mediated conversion of γ,δ-olefinic alcohols into C-glycosides

An efficient and mild intramolecular oxidative nucleophilic cyclisation protocol has been developed for the conversion of γ, δ-olefinic alcohols into the hemiketals, which in turn on deoxygenation led to the very important C-glycoside class of compounds.     

A theoretical insight into the role of counter anions and their interactions in nitropentaamminecobalt(III) toward linkage isomerism-induced photochemical motion

Density functional theory (B3LYP, B3LYP-D3, wB97XD, M062X, and M06L) and ab initio methods (MP2 and CCSD(T)) in conjunction with 6-31+G(d,p) and LanL2DZ were employed to investigate the interaction energies between [Co(NH₃)₅NO₂]²⁺ linkage isomers and chloride and nitrate in both gas phase and solid state. The nature of the chemical bonding has been analyzed by means of the atoms in molecules, electron density shift, natural bond orbitals, symmetry adapted perturbation theory, and energy decomposition analysis. The electronic structures of the two lowest laying singlet states (S_o and S₁) of [Co(NH₃)₅NO₂](NO₃)Cl isomers were also investigated using CASSCF(6,6) with LanL2DZ and 6-31G(d) basis sets. Our results show that [Co(NH₃)₅NO₂]²⁺ linkage isomers interact more strongly with chloride than nitrate. The structures of [Co(NH₃)₅NO₂](NO₃)Cl linkage isomers and their relative stabilities were examined in gas phase and in solid state and confirmed the nitro-complex as the most stable following by a viable intermediate endo-complex. Study of the nitro-nitrito linkage isomerization in [Co(NH₃)₅NO₂](NO₃)Cl revealed that anions form strong electrostatic bonds with [Co(NH₃)₅NO₂]²⁺ leading to decrease in an activation energy compared to the [Co(NH₃)₅ONO]²⁺ isomers. A concerted action of ionic interactions and hydrogen bonds are suspected of regulating the isomerization in solid state. Assessment of various DFT methods with respect to CCSD(T) suggests M062X suitable method for [Co(NH₃)₅NO₂](NO₃)Cl linkage-isomerization study. Potential energy surface calculations at the CASSCF/6-31G(d) level of theory shows that the conical intersection (S₁/S_o) might play an important role in the photoisomerization of [Co(NH₃)₅NO₂](NO₃)Cl.     

Surface functionalization chemistries on highly sensitive silica-based sensor chips

The surfaces of silica-based sensor chips, designed for evanescent-field-coupled waveguide-mode sensors, were functionalized using various surface chemistries. The immobilization of molecular entities on the functionalized silica surfaces was monitored using various microscopic techniques (scanning electron, fluorescence, and atomic force microscopies). Further, gold nanoparticle-based signal enhancement analyses were performed with protein conjugation on different functionalized surfaces using a waveguide-mode sensor. Based on these analyses, the sensor surfaces modified with glutaraldehyde (Glu) and carbonyldiimidazole were found to be good for molecules of different sizes. In addition, it can be inferred that the Glu-modified surface may be suitable for small molecules with diameters around 5 nm owing to its surface roughness. The modified surface with carbonyldiimidazole is suitable for the direct immobilization of larger molecules especially for biomolecular assemblies without intermediate chemical modifications.     

Incorporation of azo group at axial position of silatranes: synthesis,characterization and antimicrobial activity

4‐Aminoazobenzene‐derived silatranes bearing urea and aminosuccinimide as linker groups at the axial position are reported. The urea functionality is introduced in a silane ( 2 ) by the rearrangement reaction between 3‐isocyanatopropyltriethoxysilane and 4‐aminoazobenzene. N‐(3‐silatranylpropyl)‐N′‐[(p‐phenyldiazenyl)phenyl]urea and N‐[3‐(3,7,10‐trimethylsilatranyl)propyl]‐N′‐[(p‐phenyldiazene)phenyl]urea were prepared by transesterification reaction of 2 with triethanolamine and trisisopropanolamine, respectively. An efficient method for C? N bond formation is described for the synthesis of 3‐(silatranylpropyl)amino‐N‐[(p‐phenyldiazene)phenyl]pyrrolidine‐2,5‐dione and 3‐[(3,7,10‐trimethylsilatranyl)propyl]amino‐N‐[(p‐phenyldiazene)phenyl]pyrrolidine‐2,5‐dione via aza‐Michael addition reaction of aminopropylsilatranes with 4‐(N‐maleimido)azobenzene under mild conditions. All the compounds were well characterized using elemental analysis, spectroscopic techniques, thermogravimetric analysis and X‐ray diffraction. UV–visible spectroscopy indicates that the 4‐aminoazobenzene‐derived silatranes are capable acetate receptors. The synthesized compounds were screened for possible antimicrobial properties with the results showing a modest activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Concise synthesis of omega-borono-alpha-amino acids

A short protocol for the practical scale synthesis of several omega-borono-alpha-amino acids is described via the alkylation of benzophenone glycinimines with various electrophiles.     

Ferrocene substitution in amino acids strengthens the axial binding in Cu(II) complexes and separates the hydrophobic and hydrophilic region in the crystals

This paper reports on the synthesis, characterization and electrochemical properties of four ferrocenylmethyl substituted L-amino acid ligands and their Cu(II) complexes. Structural characterization of the complexes of L-methionine and L-asparagine derived ligands showed axial coordination of weak thioether and amide respectively to Cu(II). Coordination of the thioether group of L-methionine to copper (2.791 A) is shorter than observed in the electron transfer protein plastocyanin (2.9 A). Methionine thioether does not bind in synthetic Cu(II) complexes. The characterization of bis-complexes (metal : ligand ratio 1 : 2) with L-serine and L-threonine derivatives showed axial coordination of water with a shorter Cu-O bond length compared to that observed in the corresponding amino acid complexes. The structures also revealed separation of the hydrophilic and hydrophobic regions due to amino acid and ferrocene respectively which resulted in the formation of interesting H-bonded networks.