Metameric esters ketonization in the vapor phase over solid catalyst

Ketonization of metameric esters n-hexyl acetate and ethyl n-hexanoate was carried out in the vapor phase over Sn-Ce-Rh-O catalyst at 370°C and at 1 and 3 h^-1 load. In both cases the main products were dimethyl ketone, dipentyl ketone and methyl pentyl ketone; however, the compositions and ratios of the products obtained from both esters were different. The transformation pathways of both esters were inferred based on the quantitative differences in the composition of the products. The ratios of the particular compounds obtained during transformation of both esters indicate that the reactions proceeded simultaneously - through -ketoesters with partial thermal decomposition of esters and secondary condensation of the formed aldehydes. Also the way of creation of ketones resulting from secondary condensation was proposed.     

Spectrochemical Properties of Noncubical Transition Metal Complexes in Solutions. VIII. Angular Overlap Treatment of a Schiff Base Copper(II) Complex in Various Solvents

The electronic absorption spectra of trans-[Cu(Brsap)₂], where [HBrsap = 5-bromosalicylidine-o-aminopyridine (Schiff base)], were measured in various solvents at room temperature. The d-d transition energies were used to derive the angular overlap model (AOM) parameters in the C _2h symmetry. The experimental curves were resolved by Gaussian analysis. A comparison of the spectra and ligand field parameters in various solutions was made. The effect of the solvents upon the -, -bonding, and bite angle of the bidentate asymmetric ligand is discussed.     

5-(hydroxymethyl)oxazoles: versatile scaffolds for combinatorial solid-phase synthesis of 5-substituted oxazoles

A scheme combining the preparation of building blocks in solution followed by solid-phase combinatorial chemistry has been developed to side-chain diversify 5-(hydroxymethyl)oxazole scaffold (1) into aryl ethers, thioethers, sulfones, sulfonamides, and carboxamides. Protected heterocyclic scaffolds 2 were linked to the solid phase and N-terminal derivatized using active ester chemistry, providing chemset 4?1-4,1-4?. The free side-chain hydroxyl of 4 was smoothly converted to aryl ethers 6 under Mitsunobu conditions, with a broad range of substituted phenols. Alternatively, quantitative conversion of hydroxyl to bromide followed by displacement with alkyl and aryl thiols gave thioethers 8. Thioethers were optionally oxidized to sulfones 9. Bromide displacement by azide, followed by reduction to amine and acylation with a range of carboxylic acids and sulfonyl chlorides gave carboxamides 11 and sulfonamides 13, respectively. Crude purity at typically >90% was observed for each of the five modifications detailed. A series of 20 compounds, exemplifying each modification, was reprepared, purified, and fully characterized.     

Dipole‐bound anions supported by charge–transfer interaction: Anionic states of HnF3−nN → BH3 and H3N → BHnF3−n (n = 0, 1, 2, 3)

The possibility of electron binding to five molecules (i.e., F₃N → BH₃, H₂FN → BH₃, HF₂N → BH₃, H₃N → BH₂F, H₃N → BHF₂) was studied at the coupled cluster level of theory with single, double, and noniterative triple excitations and compared to earlier results for H₃N → BH₃ and H₃N → BF₃. All these neutral complexes involve dative bonds that are responsible for significant polarization of these species that generates large dipole moments. As a consequence, all of the neutral systems studied, except F₃N → BH₃, support electronically stable dipole‐bound anionic states whose calculated vertical electron detachment energies are 648 cm^?1 ([H₂FN → BH₃]^?), 234 cm^?1 ([HF₂N → BH₃]^?), 1207 cm^?1 ([H₃N → BH₂F]^?), and 1484 cm^?1 ([H₃N → BHF₂]^?). In addition, we present numerical results for a model designed to mimic charge–transfer (CT) and show that the electron binding energy correlates with the magnitude of the charge flow in the CT complex. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Chemical and Biological Characteristics of Oxytropis pseudoglandulosa Plant of Mongolian Origin

Oxytropis pseudoglandulosa is used in Mongolian traditional medicine due to its numerous reported health-promoting effects. To date, there are very few scientific reports that describe this species. In this article, its volatile oil composition, lipid extract composition, total phenolic and flavonoid content, antibacterial and allergenic properties are elucidated for the first time. Hexadecanoic acid, fokienol and tricosane were determined as the most notable components of the volatile oil, at 13.13, 11.46 and 5.55%, respectively. Methyl benzoate was shown to be the most abundant component of lipid extract at 40.69, followed by (E)-prop-2-enoic acid, 3-phenyl- and benzenepropanoic acid, at 18.55 and 9.97%. With a TPC of 6.620 mg GAE g⁻¹ and TFC of 10.316 mg QE g⁻¹, the plant extract of O. pseudoglandulosa indicated good antioxidant activity measured by IC₅₀ at 18.761 µg mL⁻¹. Of the 12 tested microorganisms, B. subtilis and S. cerevisiae were the shown to be most susceptible to the plant extract, with MIC at 2.081 and 0.260% (v/v), respectively. Bet v 1—a major birch pollen allergen found in plant-based foods—was determined to be at 192.02 ng g⁻¹ with ELISA. Such a wide spectrum of biological activity indicated by O. pseudoglandulosa lends credence for its application in food industry. Its exerted antioxidant and antimicrobial effects could improve preservation of low-processed food dedicated for consumers afflicted with allergies. Hexadecanoic acid supplemented in foods with dietary plant extracts could add to the potential anti-inflammatory impact. The analysis of lipid makeup suggests O. pseudoglandulosa extract could also be considered as natural pesticide in organic farming.     

X-ray structure and multinuclear NMR studies of platinum(II) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one

New dichloride platinum(II) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) have been synthesized and characterized by thermal analysis, infrared and ¹H, ¹³C, ¹⁵N, ¹⁹⁵Pt NMR spectroscopy. X-ray crystal structures of cis-PtCl₂(NH₃)(HmtpO) (1) and cis-PtCl₂(HmtpO)₂ · 4H₂O (2b) were determined to R = 0.0332 and R = 0.0802, respectively. In both complexes the Pt(II) ions have a square-planar geometry with two adjacent corners being occupied by two nitrogens of HmtpO molecules for 2b or NH₃ and HmtpO molecules for 1, whereas the remaining adjacent corners are occupied by two chloride anions. Spectroscopic data confirm the square planar geometry with N(3) bonded HmtpO, S-bonded dimethylsulfoxide and two trans chloride anions for trans-PtCl₂(dmso) · 4H₂O (3).     

Flavonoid and phenolic acid profile by LC-MS/MS and biological activity of crude extracts from Chenopodium hybridum aerial parts

Extracts from leaves and stems of Chenopodium hybridum were characterised for the presence and quantity of flavonoids and phenolic acids by LC-ESI-MS/MS. Five flavonoids and eight phenolic acids were detected for the first time in aerial parts of this plant species, the most abundant compounds being rutin (2.80 μg/g DW), 3-kaempferol rutinoside (2.91 μg/g DW), 4-OH-benzoic (1.86 μg/g DW) and syringic acids (2.31 μg/g DW). Extracts were tested for anti-inflammatory/antiarthritic, antihyaluronidase and cytotoxic activities against human prostate cancer (Du145, PC3) and melanoma cell lines (A375, HTB140 and WM793) of different malignancy. None of the extracts protected bovine serum albumin from heat-induced denaturation. Antihyaluronidase effect at the tested concentration was higher than standard naringenin. Cytotoxic activity was generally low with an exception of the extract from the leaves, which was found most effective against prostate Du145 cell line with 98.28 ± 1.13% of dead cells at 100 μg/mL.     

Kinetics and mechanism of formation of polymeric products during the hydroxyalkylation of parabanic acid with oxiranes

The kinetics of the reaction between N‐(2‐hydroxyalkyl) hydroparabanates (HAHP) and N,N′‐bis(2‐hydroxyalkyl) parabanates (HAP) with ethylene and propylene oxides were studied. The addition of oxiranes to imide function of HAHP led to the formation of HAP. Further reaction of HAP with oxiranes resulted in trioxoimidazolidine ring opening and polymeric products. The kinetics of the system was studied in detail. Based on the final kinetic equations, the mechanism of the reactions was postulated. The temperature dependences of kinetic parameters and analytical data provided experimental evidences supporting the mechanism. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 399–406, 2006     

Synthesis of enantiomerically pure diethyl (R)- and (S)-2-hydroxy-3-(1,2,3-triazol-1-yl)propylphosphonates

The synthesis and ee determination of diethyl 3-azido-2-hydroxypropylphosphonates from 2,3-epoxypropylphosphonates have been optimised. Enantiomerically enriched diethyl (R)- and (S)-2-hydroxy-3-(1,2,3-triazol-1-yl)propylphosphonates (R)-3a–j and (S)-3a–h as well as (S)-3j were synthesised from diethyl (R)- and (S)-2,3-epoxypropylphosphonates in a reaction sequence including azidolysis followed by 1,3-dipolar cycloaddition with selected alkynes.