Separation and Identification of Lutein Derivatives in Processed Foods

In the present work, we show that in processed sorrel, the lutein (1) can convert to 3’-epilutein (2) – 3’-stereoisomer of lutein – by epimerisation reaction, as well as to anhydrolutein I (3) and II (4) by dehydration reaction. The newly formed anhydrolutein I (3) and II (4) were detected and identified by HPLC-DAD and HPLC-MS techniques and co-chromatography with authentic samples. The compounds 1 and 2 were also isolated from cooked sorrel by column chromatography and characterized by NMR spectroscopy.     

Synthesis,characterization and thermal stability of novel carborane-containing epoxy novolacs

Carborane bisphenol novolacs(3 and 4) were synthesized in the presence of acid catalyst from carborane bisphenols(5 and 6) and formaldehyde. Further epoxidization of carborane bisphenol novolacs with epichlorohydrin gave carborane bisphenol epoxy novolacs(1 and 2). The molecular weight and epoxy value of obtained resins were determined using the molecular weight of their precursors. The epoxy values of 1 and 2 were 0.48 and 0.52 respectively, higher than the maximum theoretical epoxy value(0.45) of difunctional carborane bisphenol epoxy resins. FTIR and NMR were utilized to characterize 1 and 2. The curing behaviors were also studied by DSC and the optimized curing conditions were obtained.TGA analysis indicated that carborane moiety could shield its adjacent organic structures against initial decomposition. On the other hand, B―H on carborane cage could react with oxygen to form a three-dimensional network linked by B―O―B and B―C bonds, which further blocked the movement of formed radicals and thus the degradation process was inhibited.     

Amine electrosynthesis from 1-ethyl-4-nitro-3-cyanopyrazole

Polarography and preparative electrolysis are used to show that the electrochemical behavior of 1-ethyl-4-nitro-3-cyanopyrazole (1) in acidic aqueous-alcoholic solutions resembles the behavior of nitrobenzene. By varying the parameters of the electroreduction (ER) of compound 1, one can obtain either 1-ethyl-4-amino-3-cyanopyrazole (2) or 1-ethyl-4-amino-3-cyano-5-chloropyrazole (3). Compound 2 is formed during the ER of compound 1 in the presence of a mediator (titanium(III)) at temperatures below 10°C. Compound 3 is produced by the direct reduction of compound 1 on a lead electrode (30% ethanol, 10% HCl). The yield of amine chlorohydrates 2 and 3 is 56 and 92%, respectively. The mediated ER of compound 1 at catholite temperatures higher than 10°C yields a mixture of compounds 2 and 3; the proportion of the latter increases with temperature to become the major product at 60°C. Compound 3 is formed due to the rearrangement of the hydroxylamine derivative produced by the ER of compound 1, followed by the substitution of chlorine for the hydroxy group.     

The conformational spaces of dinaphthyl ketones,dinaphthyl thioketones,and dinaphthyl diazomethanes: 1-substituted naphthalenes versus 2-substituted naphthalenes

1,1′-Dinaphthyl ketone (15), 1,2′-dinaphthyl ketone (18), 2,2′-dinaphthyl ketone (19), 1,1′-dinaphthyl thioketone (16), 1,2′-dinaphthyl thioketone (20), 2,2′-dinaphthyl thioketone (21), 1,1′-dinaphthyldiazomethane (17), 1,2′-dinaphthyldiazomethane (22), and 2,2′-dinaphthyldiazomethane (23) have been synthesized. Ketone 15 has been prepared from di(1-naphthyl)methanol; ketone 18 has been prepared by a Friedel–Crafts acylation of naphthalene with 2-naphthoyl chloride; ketone 19 has been prepared by a Grignard reaction of 2-naphthylmagnesium bromide with 2-naphthoyl chloride. Thioketones 16, 20, and 21 have been prepared by reactions of the corresponding ketones 15, 18, and 19 with Lawesson’s reagent. The diazomethane derivatives 17, 22, and 23 have been prepared by the HgO oxidation of the respective hydrazones 25, 27, and 28 (prepared from the respective thioketones 16, 20, and 21). The crystal and molecular structures of ketones 15, 18, and 19 and of thioketone 16 have been determined. A variety of conformations in the crystal structures is noted: 1Z,1′Z (15), 1E,1′Z (16), 1E,2′E (18), 2Z,2′Z (19). The NMR experiments have demonstrated the downfield shifts of the protons peri to the carbonyl and the thiocarbonyl groups in 15, 16, and 18, but not in 20. A systematic DFT study (B3LYP/6-31G(d)) of the conformational spaces of 15–23 and their ¹H and ¹³C NMR chemical shifts has been performed. In each series of constitutional isomers, the order of stabilities is 2,2′-(NA)₂C=X > 1,2′-(NA)₂C=X > 1,1′-(NA)₂C=X. The decrease in the stabilities of 1-naphthyl derivatives relative to 2-naphthyl derivatives is attributed to the increased overcrowding and the increased twist angles in 1-naphthyl derivatives. The increased stabilization of E-conformations with the increase of the radius of a heteroatom at C⁹ due to the steric reasons is noted. The DFT calculations satisfactorily describe the X-ray conformations of 15, 16, 18, and 19.     

Influence of the nature of the substituent in 3-(2-pyridyl)-1,2,4-triazole for complexation with Pd<Superscript>2+</Superscript>

The structure of four new palladium complexes [Pd(HL ² )Cl ₂ and Pd(L ^1–3 ) ₂ ] with 3-(2-pyridyl)-5-R-1,2,4-triazoles (R=H, CH₃, Ph respectively HL ¹ , HL ² , HL ³ ) was proposed based on IR, NMR, UV spectroscopy and MALDI mass spectrometry data analysis. It is found that the complexation of HL ² and HL ³ with Pd²⁺ ions results in a decrease of their fluorescence intensity and it is vice versa in case of HL ¹ . Furthermore, the influence of the substituent (R) in the 3-(2-pirydyl)-5-R-1,2,4-triazoles on the fluorescent and protolytic properties of HL ^1–3 was investigated.     

Influence of medium viscosity on photophysical properties of kynurenic acid and kynurenine yellow

Dependences of the fluorescence and triplet state quantum yields of kynurenic acid (1) and kynurenine yellow (2) in water—glycerol mixtures on medium viscosity have been studied. The main channel of the singlet excited state decay of compound 1 is the intersystem crossing, which rate weakly depends on the viscosity; only a small (approximately 1.5-fold) increase in the fluorescence yield was found for this compound with the increase of the solution viscosity from 0.84 cP (aqueous solution) to 78 cP (86% glycerol). The deactivation of the S₁ state of compound 2 is caused mainly by the internal conversion, and a noticeable increase of the fluorescence yield (approximately 3-fold), as well as the change in the photolysis product yields, was observed with the increasing percentage of glycerol in the mixture. The triplet state quantum yields for compounds 1 and 2 remained unchanged with the variation of the glycerol content in the mixture.     

Synthesis,antibacterial activity,and fluorescence properties of a novel series from [2,4-dioxochromen-3(4<Emphasis Type="Italic">H</Emphasis>)methyl]amino acid

A new solvent-free method for synthesis of starting compounds 2,4-dioxochromen-3(4H)methyl amino acetic acid derivatives 1a–e via a green approach is reported. Also, the behavior of compound 1a towards various nitrogen nucleophiles such as primary amines, hydrazine hydrate, and hydroxylamine hydrochloride to give corresponding compounds 2–4 was studied. Furthermore, chlorination of compound 1a using a mixture of PCl₅/POCl₃ to yield acid chloride derivative 5 and the reaction of the latter compound 5 with various amino acids to obtain dipeptide compounds 6a–e are described. Moreover, cyclization of compound 1a in alkaline medium to afford dihydrochromeno[3,4-c]pyrrole-1-carboxylic acid 7 and cyclization of 6b in acidic medium, namely Ac₂O, to yield piperazine derivative 8 are reported. Also, reaction of compound 1a with maleic anhydride in dioxane to afford Diels–Alder adduct 9, which posteriorly reacted with hydrazine hydrate to give 10, was investigated. Most of the newly synthesized compounds were screened against Gram-positive and Gram-negative bacteria, with compound 5 exhibiting the maximum inhibition zone towards all four types of bacteria. In addition, the absorption and fluorescence emission of some of the substituted coumarins were studied in dioxane, revealing that the substituents altered both the absorption and fluorescence emission maxima.     

Syntheses and crystal structures of two self-assembled dizinc(II) helicates with novel hydrazone linked polypyridyl ligands

The rationally designed polydentate ligands, L ¹ and L ² , based on the pyridinyl moiety and the hydrazone fragment have been synthesized to coordinate zinc(II) ions. We utilize pyridine as a rigid core connecting two bipyridines as ligand building blocks with a hydrozone linker for the L ¹ . The L ² has a reversed design in which a bipyridine was used as a hinging-available building block of the ligand core, connecting two pyridazine arms with a hydrazone linker. Two novel helical dizinc(II) complexes were obtained by the reaction of L ¹ and L ² with zinc(II) perchlorate in acetonitrile. The structures of both helicates were confirmed by X-ray diffractometry. Single-stranded helicate Zn ₂ L ¹ contains two zinc ions bridged by an oxygen atom. Except for the L ² ligand, no other bridging species were found between the two zinc ions in the double-stranded helicate Zn ₂ L ₂ ² . The self-assembling process of helicate Zn ₂ L ¹ in solution state was studied by UV–Vis spectrometric titration experiments. The stepwise formation constants imply a slightly positive cooperative behavior for the formation of helicates.     

Improved synthesis and low-temperature performance of a series of saturated α-branched fatty acids

Five saturated α-branched fatty acids, also known as Guerbet acids, including α-propylhexyl acid (G ₁ ), α-butylhexyl acid (G ₂ ), α-propyloctyl acid (G ₃ ), α-butyloctyl acid (G ₄ ), and α-hexyloctyl acid (G ₅ ), were synthesized in high yields by four-step reaction. Colorless, almost odorless, and oily products were obtained with high purity, whose structures were confirmed by GC, ¹H/¹³C NMR, and ESI–MS characterization. G ₁ , G ₃ , and G ₄ had pour points lower than ?60 °C, while G ₂ and G ₅ showed higher pour points (?42 °C and 6 °C, respectively) because of their molecular symmetry. Considering the low-temperature properties, G ₁ , G ₃ , G ₄ , and even G ₂ held great potential applications in the lubricant and oilfield.     

Synthesis and in vitro cytotoxic evaluation of some novel hexahydroquinoline derivatives containing benzofuran moiety

A series of new ethyl 4-(2-(benzofuran-2-yl)-4-substituted-1,4,5,6,7,8-hexahydroquinolin-1-yl)-benzoate 3a–c was synthesized by Michael condensation of benzofuran chalcones 1a–c and cyclohexanone to give 2-(2-benzofuranyl)-4-substituted-5,6,7,8-tetrahydro-4-H -chromene 2a–c, followed by reaction of the latter with ethyl 4-aminobenzoate. Condensation of 3a–c with different amines afforded the corresponding amides 4a–e. On the other hand, upon treatment compounds 3a–c with hydrazine hydrate gave the benzohydrazide derivatives 5a–c. The reaction of compounds 5a–c with different thio/isocyanate gave the corresponding thiosemicarbazide and semicarbazide derivatives 6a–c. Meanwhile compounds 5a–c were reacted with ethyl cyanoacetate and different β-dicarbonyl compounds such as acetyl acetone, ethyl acetoacetate, and diethyl malonate to afford pyrazolyl derivatives 7a, b; 8a, b; 9a, b; and 10a–c, respectively. Moreover, 5a–c were reacted with carbon disulfide to synthesize the corresponding oxadiazolyl derivatives 11a–c, while their condensation with different aromatic aldehydes gave the corresponding Schiff bases 12a–d. Cytotoxic evaluation of some of the newly synthesized compounds against human hepatocellular carcinoma cell lines (HepG-2) revealed that the tested compounds produce promising inhibitory effect against the growth of HepG-2 cells with IC₅₀ values ranged from 11.9 to 19.3 µg/mL.     

Syntheses,structures, and solid-state phosphorescence characteristics of <Emphasis Type="Italic">trans</Emphasis>-bis(salicylaldiminato)Pt(II) complexes bearing perpendicular <Emphasis Type="Italic">N</Emphasis>-aryl functionalities

The syntheses, structures, and solid-state emission characteristics of trans-bis(salicylaldiminato)Pt(II) complexes bearing N-aromatic functionalities are described herein. A series of Pt complexes bearing various N-phenyl (1) and N-(1-naphthyl) (2) groups on the salicylaldiminato ligands were prepared by reacting PtCl₂(CH₃CN)₂ with the corresponding N-salicylidene aromatic amines, and the trans-coordination and crystal packing of these complexes were unequivocally established based on X-ray diffraction (XRD). Complexes with 2,6-dimethylphenyl (1c), 2,6-diisopropylphenyl (1d), 1-naphthyl (2a), and 1-(2-methylnaphthyl) (2b) groups on the N atoms exhibited intense phosphorescent emission at ambient temperature in the crystalline state, while those with phenyl (1a), 2,6-dibromophenyl (1b), and 2,6-bis(N,N-dimethylamino)phenyl (1e) functionalities were either less emissive or non-emissive under the same conditions. XRD analyses identified significant intramolecular interactions between Pt and H atoms of the N-aryl functionalities in the emissive crystals of 1c, 1d, and 2a. These interactions were evidently an important factor associated with intense emission at ambient temperature.     

A green,simple, catalyst-free,and efficient method for electro-organic synthesis of new benzofuran derivatives

In this work, the electrochemical oxidation of catechols 1a and 1b was studied in the presence of pyrazolidine-3,5-dione (3a), as a nucleophile, in a mixture of ethanol and a phosphate buffer solution (0.1 M, pH 7), as a green medium, using the cyclic voltammetry and controlled-potential coulometry techniques. The results obtained indicated that the oxidized forms of these catechols (2a and 2b) participated in the Michael addition reactions with pyrazolidine-3,5-dione (3a), and converted, via an ECEC mechanism, to their corresponding benzofurans (7a and 7b). In this work, some new benzofuran derivatives were synthesized with good yields and high purities using a facile, one-pot, and environmentally friendly electrochemical method in the absence of any chemical catalyst, toxic solvent, and hard conditions.     

Gas Chromatographic – Mass Spectrometric Cardiotonic Glycosides Detection in Equine Urine Doping Analysis

A screening method for the detection of cardiotonic glycosides in horse’s urine is presented in this paper. This method is based on the detection by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-high resolution mass spectrometry (GC-HRMS) of the trimethylsilyl (TMS) derivatives of the aglycon moieties of these compounds after solid phase extraction and methanolysis, according to the standard procedure currently used for the screening of anabolic steroids in horses, in the Athens Doping Control Laboratory. This validated method was also applied for the excretion study of digoxin in two mare horses after a single administration of a 75 μg Kg^?1 oral dose, by GC-MS and GC-HRMS.     

Tuning the regioselectivity of (benzimidazolylmethyl)amine palladium(II) complexes in the methoxycarbonylation of hexenes and octenes

Reactions of N-(1H-benzoimidazol-2-ylmethyl-2-methoxy)aniline (L1) and N-(1H-benzoimidazol-2-ylmethyl-2-bromo)aniline (L2) with p-TsOH, Pd(AOc)₂ and two equivalents of PPh₃ or PCy₃ produced the corresponding palladium complexes, [Pd(L1)(OTs)(PPh₃)] (1), [Pd(L2)(OTs)(PPh₃)] (2) and [Pd(L1)(OTs)(PCy₃)] (3), respectively, in good yields. The new palladium complexes 1–3 and the previously reported complexes [Pd(L1)ClMe] (4) and [Pd(L2)ClMe] (5) gave active catalysts in the methoxycarbonylation of terminal and internal olefins to produce branched and linear esters. The effects of complex structure, nature of phosphine derivative, acid promoter and alkene substrate on the catalytic activities and selectivity have been studied and are herein reported.     

Facile synthesis of some condensed 1,3-thiazines and thiazoles under conventional conditions: antitumor activity

1,3-Thiazine 3 was obtained from cinnamoyl thiourea derivative 2 as the kinetic control product. Refluxing of 2 with sodium ethoxide afforded pyrimidine derivative 4. Moreover, stirring of 2 with bromine/acetic acid gave thiazole 5 that was condensed with o-phenylene diamine forming benzimidazole 6. Heating of arylthiourea 8 with maleic anhydride or phenacyl chloride afforded thiazole derivatives 9 and 10, respectively. Condensation of compound 10 with o-phenylene diamine gave benzimidazole 11. Reaction of p-amino benzoic acid with chloro acetyl isothiocyanate, acetylacetone and ethylacetoacetate produced imidazole 14, enaminone 15 and crotonate 16 derivatives, respectively. Stirring a mixture of benzoyl isothiocyanate with 15 and/or 16 resulted in pyridine-2-thione 17. The yields of the prepared compounds were 41–93%. The experimental section is simple and easy. The detailed synthesis, spectroscopic data, IC₅₀ and antitumor activity of the synthesized compounds were reported. The cytotoxicity of the newly synthesized products showed that compound 4 is the most active compound towards the cancer cell line at which its reactivity is higher than that of the standard doxorubicin (anticancer reference drug).     

Exploring the impacts of the vinylogous anomeric effect on the synchronous early and late transition states of the hydrogen molecule elimination reactions of cis-3,6-dihalocyclohexa-1,4-dienes

LC-ωPBE, B3LYP, and M06-2X methods with the 6–311+G** basis set on all atoms and natural bond orbital (NBO) interpretation were performed to investigate the roles and contributions of the effective factors on the potential energy surfaces of the hydrogen molecule elimination reactions of cyclohexa-1,4-diene (1) and its cis-3,6-dihalo derivatives [halogen=F (2), Cl (3), Br (4)] to hydrogen molecule and their corresponding aromatic rings. The ring puckering in compound 2 (which results from the repulsive electrostatic interactions between the natural bond orbital dipole moments of two C-F bonds) shortens the allylic hydrogen atoms’ distance, leading to the smaller barrier height in compound 2 compared to that in compound 1. The barrier heights of the hydrogen molecule elimination reactions increase from compounds 2 to 4 while their corresponding exothermic characters decrease. The variations of the advancements of transition state structures (δB _av) reveal that the hydrogen molecule elimination reactions of compounds 2–4 do not obey the Hammond-Leffler postulate. In compound 2, the ring puckering shortens the allylic hydrogen distance (d _H8-H10) while d _H8-H10 values increase going from compounds 2 to 4, leading to the increase of their corresponding hydrogen molecule elimination reactions barrier heights. Interestingly, the variations of the vinylogous hyperconjugative anomeric effects justify the directions of the rings puckering going from compounds 2 to 4. The increase of the activation exchange components [PETR _(TS)-PETR _(GS)] going from compounds 2 to 4 correlates well with their corresponding hydrogen molecule elimination process barrier heights.     

Ring-opening polymerization of ε-caprolactone catalysed by (pyridyl)benzoazole Zn(II) and Cu(II) complexes

This paper describes the synthesis of (pyridyl)benzoazole Zn(II) and Cu(II) complexes and their applications as catalysts in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). Reactions of 2-(3-pyridyl)-1H-benzimidazole (L1), 2-(2-pyridyl)-1H-benzothiazole (L2) and 2-(2-pyridyl)-1H-benzimidazole (L3) with Zn(II) and Cu(II) acetates produced the corresponding complexes; [Zn₂(L1)₂(OAc)₄)] (1), [Cu₂(L1)₂(OAc)₄] (2), [Zn(L2)(OAc)₂)] (3), [Zn(L3)(OAc)₂)] (4) and [Cu(L3), (OAc)₂)] (5). Molecular structures of complexes 2 and 5a revealed that while L1 adopts a monodentate binding mode, through the pyridyl nitrogen atom, L3 exhibits a bidentate coordination mode. All the complexes formed active catalysts in the ROP of ε-CL to afford moderate molecular weight polymers. The kinetics of the ROP reactions of ε-CL were pseudo-first-order with respect to monomer and catalysts.     

Low-melting molecular complexes: Part VII. 2,3-, 2,5- and 3,4-hexanediones and their molecular complexes with chloroform

Crystals of three isomeric 2,3-, 2,5- and 3,4-hexanediones 1–3 and of molecular complexes (1:2) of 2 and 3 with chloroform (4 and 5) were grown by in situ cryocrystallisation and characterised by single-crystal X-ray crystallography. The intermolecular interactions and packing motifs were examined using the analysis of pairwise energies of intermolecular interactions. The method has revealed the importance of carbonyl…carbonyl interactions in the structures 1, 3 and 4 and the relatively weaker halogen bonds in the structures 4 and 5.     

Benzyl group conformation in 4-benzyl-4-hydroxypiperidines

The high-resolution ¹H and ¹³C NMR spectra of eight 4-benzyl-4-hydroxypiperidines 1–8 were recorded in CDCl₃ and analyzed. In 2, the conformation of the equatorial benzyl group at C(4) was established as an equilibrium mixture of A [the phenyl group is gauche with respect to OH and C(5)] and B [the phenyl group is gauche with respect to OH and C(3)], whereas in 3-alkyl-4-benzyl-4-hydroxypiperidines 3–8, the favored conformation of the benzyl group at C(4) is A. In 1, the axial benzyl group at C(4) adopts the gauche conformations A′ [the phenyl group is gauche with respect to OH and C(3)] and B′ [the phenyl group is gauche with respect to OH and C(5)], in which the phenyl ring of the benzyl group is gauche with respect to the OH group. The HF/DFT B3LYP/6-3G* hybrid calculations of model systems 1′–3′ also support these conformations. The ¹³C data reveal that the equatorial methyl group at C(3) exerts a shielding influence on the methyl-bearing carbon and the magnitude of the α effect was found to be approximately ?1.5 ppm. The parameters of the ¹³C substituent in the benzyl group show that the the α effect of the equatorial benzyl group is considerably higher in 3-ethyl tertiary alcohol 7 than in 3-methyl tertiary alcohol 3 and 4-benzyl-t(4)-hydroxypiperidine 2. This may be explained if we take into account the different conformations of the ethyl group in t(4)-hydroxy-3-ethyl-2,6-diphenylpiperidine 12 and 3-ethyl tertiary alcohol 7.     

Transition metal complexes of a hydrazone derived from hydralazine hydrochloride and 3,5-di-tert-butylsalicylaldehyde

Mononuclear Co(III), Ni(II) and Cu(II) coordination compounds of (E)-1-(3,5-di-tert-butyl-2-hydroxybenzylidene)-2-(phthalazin-1-yl)hydrazine (LH) were prepared and characterized by physicochemical and spectroscopic methods. The metal-to-ligand ratio was found to be 1:2 in [Co(L)₂]Cl·2H₂O (1) and [Ni(L)₂]·2H₂O (2), while it is 1:1 in [Cu(L)Cl]·2CH₃OH (3). The X-ray crystal structures of LH and complex 1 is are reported. LH shows monobasic behavior, coordinating through NNO donor atoms. The complexes were investigated for their antimicrobial properties. Complexes 1 and 3 show excellent antibacterial and antifungal activities, respectively.