Structural investigation on hexasubstituted benzene derivatives. Part 2: The structure of metadinitrotetramethylbenzene and molecular mechanics analysis on meta and ortho derivatives

C₁₀H₁₂N₂O₄ (M r=224.2) crystallizes in the monoclinic system, space groupP2₁/mwitha=15.462(4),b=7.926(3),c=8.972(3) Å;=90.2(1)°;V=1099.5(6) ų;Z=4;D _c=1.35 gcm^–3;(Cu-K)=8.6 cm^–1; =1.5418 Å;F(000)=472. The position of the molecule on a crystallographic mirror plane forces the NO₂ plane to be normal to the benzene ring. The-electron-withdrawing character of the NO₂ groups induces a deformation on the geometry of the benzene.     

Enlarging the size of calix[4]arene-crowns-6 to improve Cs/K selectivity: a theoretical and experimental study

Ab initio calculations in the gas-phase indicate that the substitution of an ethylene with a propylene moiety in the polyether bridge of 1,3-di-iso-propoxycalix[4]arene-crowns-6 could result in an enhanced Cs⁺/K⁺ selectivity which is of particular interest in nuclear waste treatment. We therefore synthesised two novel calix[4]arene-crown-6 compounds (1 and 2) having a propylene moiety in their structure and for this named calix[4]arene-propylene-crown-6. The structures of compounds 1 and 2 were elucidated by NMR in solution and for 1 also by X-ray diffraction studies in the solid state. Association constants (K_a) in CHCl₃ of the two novel calix-crowns were measured and pointed out a plateau selectivity towards alkali metal ions which was not predicted by molecular modelling calculations. These results indicate the important role played by the solvent molecules and counter-anions in binding for this class of ionophores.     

A convenient laboratory synthesis of 2-oxazoline

The reaction of 2-chloroethylformamide ( 1a ) with sodium hydride, in N-methyl-2-pyrrolidone, at reduced pressure, gave anhydrous 2-oxazoline ( 2a ) in good yield.     

Asymmetric synthesis by chiral ruthenium complexes : IV. Reduction of carbon-carbon double bonds in prochiral α,β-unsaturated carboxylic acids by hydrogen transfer catalysed by H4Ru4(CO)8[(−)-DIOP]2

The enantioface-discriminating hydrogen transfer reduction of αβ-unsaturaged acids takes place at 120°C in the presence of H₄Ru₄(CO)₈[()-DIOP]₂. Secondary alcohols are satisfactory hydrogen donors. Selectivity, optical yields, and rates are lower than those obtained when working in the presence of hydrogen under pressure.     

Emerging Molecular Receptors for the Specific-Target Delivery of Ruthenium and Gold Complexes into Cancer Cells

Cisplatin and derivatives are highly effective in the treatment of a wide range of cancer types; however, these metallodrugs display low selectivity, leading to severe side effects. Additionally, their administration often results in the development of chemoresistance, which ultimately results in therapeutic failure. This scenario triggered the study of other transition metals with innovative pharmacological profiles as alternatives to platinum, ruthenium- (e.g., KP1339 and NAMI-A) and gold-based (e.g., Auranofin) complexes being among the most advanced in terms of clinical evaluation. Concerning the importance of improving the in vivo selectivity of metal complexes and the current relevance of ruthenium and gold metals, this review article aims to survey the main research efforts made in the past few years toward the design and biological evaluation of target-specific ruthenium and gold complexes. Herein, we give an overview of the inorganic and organometallic molecules conjugated to different biomolecules for targeting membrane proteins, namely cell adhesion molecules, G-protein coupled receptors, and growth factor receptors. Complexes that recognize the progesterone receptors or other targets involved in metabolic pathways such as glucose transporters are discussed as well. Finally, we describe some complexes aimed at recognizing cell organelles or compartments, mitochondria being the most explored. The few complexes addressing targeted gene therapy are also presented and discussed.     

Synthesis of 5-amino-1,2,3,4-tetrahydrobenzo[b][1,7]naphthyridines and 2,3,4,4a,5,6-hexahydrobenzo[c][2,6]naphthyridines

This paper describes the synthesis of some 5-amino-1,2,3,4-tetrahydrobenzo[b][1,7]naphthyridines and 2,3,4,4a,5,6-hexahydrobenzo[c][2,6] naphthyridines starting from anilines and 1-benzyl-4-ethoxycarbonylpiperidin-3-one. The compounds were prepared in order to study their potential acetylcholinesterase inhibitory activity.     

Characterization of a new non-centrosymmetric polymorph of diphenyl-1,3,4-oxadiazole

Diphenyl-1,3,4-oxadiazole (DPO) crystallization experiments from solutions clearly reveal the polymorphism of the substance. Besides the formerly known centrosymmetric monoclinic structure with space group P2₁/c (DPO I) a new monoclinic structure with the non-centrosymmetric space group Cc is found (DPO II): a=2.4134(4) nm, b=2.4099(3)  nm, c=1.2879(2) nm, β=110.048(3)°, and V=7.0363(17) nm³. The asymmetric unit contains six independent molecules in a complex packing motif. A re-determination of the crystal structure of DPO I at room temperature gives lattice parameters a=0.51885(6) nm, b=1.8078(2) nm, c=1.21435(14) nm, β=93.193(3)°, and V=1.1373(2) nm³. X-ray measurements at 363 K show a significant increase of the unit cell volume by 1.6%. Differences between both structures concerning morphology and characteristic Raman bands are outlined in detail. DSC investigations show an irreversible transition from DPO I to DPO II at 97 °C. DPO II does not show any transition in the temperature range up to the melting point at 141 °C. The non-centrosymmetric DPO II structure shows triboluminescence.     

Catalytic asymmetric ring opening of 2,3-substituted norbornenes with organometallic reagents: a new formal aza functionalization of cyclopentadiene

An unprecedented regioselective and anti stereoselective asymmetric ring opening of 1,3-cyclopentadiene-heterodienophile cycloadducts, including also 2,3-diazabicyclo[2.2.1]heptenes, with hard alkylmetals and copper-phosphoramidite catalysts, is reported. The induced ring opening, in conjunction with C-C bond formation, gives a catalytic and practical access to new heterofunctionalized cyclopentenes in an enantioenriched form (up to 86% ee). [reaction: see text]     

Combination of Natural Extracts and Photobiomodulation in Keratinocytes Subjected to UVA Radiation

Natural extracts (NE) with antioxidant properties can minimize the effects of photoaging. Photobiomodulation (PBM) has proven to be a useful tool for the modulation of cell metabolism. Here, we investigate the associations of antioxidants with PBM with the aim of promoting skin rejuvenation. We began with standardization of the experimental protocol. Extracts of chamomile, rosemary, blueberry, green tea, figs, pomegranate and nutwood were tested. A custom irradiation system (366 ± 10 nm) was used to simulate sun exposure. A light emitting diode system (640 ± 12.5 nm) was used for PBM. Viability assessments were performed by the (3‐(4,5‐Dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) MTT assay method. Based on the results, radiant exposure to UVA was defined as 9 and 1 J cm^?2 for PBM. Extract concentrations were established on the basis of dark toxicities, which ranged from 0.01% to 0.3%. The data show that PBM is a promising therapy to restore keratinocytes after UVA damage; however, the detailed mechanism and effects require further exploration. Moreover, although the combination of PBM with NE may be a useful strategy, the choice of a NE is challenging, since the working concentration and other properties, such as photosensitivity, may bring about unwanted results.