Ortho‐hydroxyl effect and proton transfer via ion–neutral complex: the fragmentation study of protonated imine resveratrol analogues in mass spectrometry

The fragmentation pathways of protonated imine resveratrol analogues in the gas‐phase were investigated by electrospray ionization–tandem mass spectrometry. Benzyl cations were formed in the imine resveratrol analogues that had an ortho‐hydroxyl group on the benzene ring A. The specific elimination of the quinomethane neutral, CH₂ = C₆H₄ = O, from the two isomeric ions [M1 + H]⁺ and [M3 + H]⁺ via the corresponding ion–neutral complexes was observed. The fragmentation pathway for the related meta‐isomer, ion [M2 + H]⁺ and the other congeners was not observed. Accurate mass measurements and additional experiments carried out with a chlorinated analogue and the trideuterated isotopolog of M1 supported the overall interpretation of the fragmentation phenomena observed. It is very helpful for understanding the intriguing roles of ortho‐hydroxyl effect and ion–neutral complexes in fragmentation reactions and enriching the knowledge of the gas‐phase chemistry of the benzyl cation. Copyright © 2016 John Wiley & Sons, Ltd.     

Polymorphism of methyl 4‐amino‐3‐phenylisothiazole‐5‐carboxylate: an experimental and theoretical study

Being a close analogue of amflutizole, methyl 4‐amino‐3‐phenylisothiazole‐5‐carboxylate (C₁₁H₁₀N₂O₂S) was assumed to be capable of forming polymorphic structures. Noncentrosymmetric and centrosymmetric polymorphs have been obtained by crystallization from a series of more volatile solvents and from denser tetrachloromethane, respectively. Identical conformations of the molecule are found in both structures. The two polymorphs differ mainly in the intermolecular interactions formed by the amino group and in the type of stacking interactions between the π‐systems. The most effective method for revealing packing motifs in structures with intermolecular interactions of different types (hydrogen bonding, stacking, dispersion, etc.) is to study the pairwise interaction energies using quantum chemical calculations. Molecules form a column as the primary basic structural motif due to stacking interactions in both polymorphic structures under study. The character of a column (straight or zigzag) is determined by the orientations of the stacked molecules (in a `head‐to‐head' or `head‐to‐tail' manner). Columns bound by intermolecular N—H…O and N—H…N hydrogen bonds form a double column as the main structural motif in the noncentrosymmetric structure. Double columns in the noncentrosymmetric structure and columns in the centrosymmetric structure interact strongly within the ab crystallographic plane, forming a layer as a secondary basic structural motif. The noncentrosymmetric structure has a lower density and a lower (by 0.59 kJ mol^?1) lattice energy, calculated using periodic calculations, compared to the centrosymmetric structure.     

Solvothermal synthesis and removal capacity for hydrogen chloride gas of Zn(OH)(NO3) with a rare (10,3)-d net

A basic zinc nitrate, [Zn(OH)(NO₃)]_n with a novel framework reported herein is prepared by solvothermal synthesis, and holds a rare three-dimensional (10,3)-d net called by Wells. It crystallizes in orthorhombic, space group, Pna2₁ (No. 33), , , , Z=4, , , , 3.49<θ<27.51, , R₁=0.029, wR₂=0.0773 for 697 (I>2σ(I)) of 1728 [R_(int)=0.0246] unique reflections and 59 parameters. GOF=1.073. Interestingly this basic zinc nitrate, [Zn(OH)(NO₃)]_n behaves well at removal capacity for hydrogen chloride gas, 20.3 g HCl/100 g, and its framework is not destroyed yet. This adsorption character may be useful for the removal of toxic gases in the environment.     

A new approach towards peptidosulfonamides: synthesis of potential inhibitors of bacterial peptidoglycan biosynthesis enzymes MurD and MurE

Peptidosulfonamides are an emerging group of peptidomimetics with a variety of applications in medicinal chemistry. We present a novel approach to the synthesis of peptidosulfonamides, and apply it to a series of new potential inhibitors of the bacterial peptidoglycan biosynthesis enzymes MurD and MurE. The synthesis was conducted via N-phthalimido β-aminoethanesulfonyl chlorides, which are new building blocks for the synthesis of peptidosulfonamides. In the most crucial step, sulfonic acids or their sodium salts were converted into the corresponding sulfonyl chlorides using an excess of either SOCl₂ or SOCl₂/DMF, and then coupled to the C-protected amino acid. None of the compounds significantly inhibited MurD, however, some inhibited MurE; one had an IC₅₀ below 200 μM, which constitutes a promising starting point for further development. Molecular modelling simulations were performed on two analogues to investigate the absence of inhibitory activity of the sulfonamide compounds on MurD.     

Model dipeptides incorporating the trans cyclohexane analogues of phenylalanine: further evidence of the relationship between side-chain orientation and β-turn type

In order to study the influence of the side-chain orientation on the peptide backbone conformation we have synthesised the model dipeptides t-BuCO-l-Pro-(1S,2R)-c₆Phe-NHMe and t-BuCO-l-Pro-(1R,2S)-c₆Phe-NHMe, incorporating each enantiomer of the trans cyclohexane analogue of phenylalanine (trans-1-amino-2-phenylcyclohexanecarboxylic acid). The orientation of the aromatic side-chain determines the β-turn type accommodated by these peptides to the point that the (1S,2R)-c₆Phe derivative retains the type I β-turn in the crystalline state, in contrast to the behaviour exhibited by the natural counterpart t-BuCO-l-Pro-l-Phe-NHMe.     

?-3-O-酰基-2-O-苄基-甘油二烷基磷酸酯的合成和结构表征

?-3-O-酰基-2-O-苄基-甘油二烷基磷酸酯的合成和结构表征; ?-O-酰基-O-苄基-甘油二烷基磷酸酯;磷脂类似物;生物活性物质     

A New Synthetic Approach to Elvucitabine

A new synthetic approach to elvucitabine started from L-xylose via the reactions of 10 steps in an overall yield of 20% was developed. The key steps included trimethylsilyl trifluoromethanesulfonate(TMSOTf)-mediated stereocontrolled β-glycosidation and exquisite choice of chloroacetyl group for the protection of hydroxyl groups as well as the corresponding deprotection under notably mild conditions. The structure of elvucitabine, in particular, the stereochemistry thereof, was unambiguously determined by comparison of the physical properties, such as ¹H NMR data and the specific rotation, of the synthesized sample with those reported.     

Biological properties of two enantiomorphic forms of N‐(2,6‐dimethylphenyl)‐4‐hydroxy‐2,2‐dioxo‐1H‐2λ6,1‐benzothiazine‐3‐carboxamide,a structural analogue of piroxicam

The title benzothiazine‐3‐carboxamide, C₁₇H₁₆N₂O₄S, crystallized in two enantiomorphic crystal forms with the space groups P3₂ and P3₁ despite the absence of a classic stereogenic atom. The molecular structures are mirror images of each other. Only one sulfonyl O atom takes part in intramolecular hydrogen bonding as a proton acceptor and this atom is different in the two enantiomorphic structures. As a result, the S atom becomes a pseudo‐stereogenic centre. This fact is worth taking into account due to the different biological activities of the enantiomorphic forms. One form possesses a high analgesic activity, while the other form revealed a high anti‐inflammatory activity.     

A new analog of pyrrolezanthine from the roots of Reynoutria ciliinervis (Nakai) Moldenke

In the present study, a new analogue of pyrrolezanthine (1) was isolated from the roots of Reynoutria ciliinervis (Nakai) Moldenke. Its structure was elucidated mainly by NMR, HR-ESI-MS and the single-crystal X-ray diffraction spectroscopic data. Meanwhile, the antimicrobial activity of compound 1 was measured, it exhibited potent antifungal activity against Sclerotinia sclerotiorum with MIC value of 31.2 μg/mL.     

Bimetallic CuCo Derived from Prussian Blue Analogue for Nonenzymatic Glucose Sensing

Bimetallic CuCo composites are prepared by calcinating copper hexacyanocobaltate precursor in N₂ atmosphere. The CuCo modified electrodes are fabricated for nonenzymatic glucose sensing in the alkaline electrolyte. The glucose can be directly electro-oxidized on the surface of the electrode catalyst mediated by the redox couples of Cu and Co. The optimal glucose sensor exhibits a high sensitivity (567 μA ⋅ mM⁻¹ ⋅ cm⁻²) in the range up to 825 μM with a detection limit of 3 μM and acceptable selectivity. The sensor can also be applied in serum samples. This work provides a facile and easily-scalable synthesis method of electrocatalysts for nonenzymatic glucose sensors.