Triterpenoid Saponins from Vaccaria segetalis

Four novel triterpenoid saponins, Vaccariside B‐E (1–4), were isolated from the seeds of Vaccaria segetalis and their structures were elucidated as 3‐O‐β‐D‐galactopyranosyl‐(1–2)‐β‐D‐glucuronopyranosyl quillaic add 28‐O‐β‐D‐xylopyranosyl‐(1–3)‐α‐L rhamno‐pyranosyl‐(1–2)‐[α‐L‐arabinofura‐nosyl‐(1–3)]‐4‐O‐acetyl‐β‐D)‐fucopyranoside (1), 3‐O‐β‐D‐galactopyranosyl ‐ (1–2) ?3‐O‐acetyl‐β‐D ‐ glucuronopyranosyl quillaic acid 28‐O‐β‐D‐xylopyranosyl‐(1–3)‐α‐L‐rhamnopyra‐nosyl‐(1–2)‐[α‐L‐arabinofuranosyl‐(1–3)]‐4‐O‐acetyl‐β‐D‐fucopyranoside (2), 3‐O‐β‐D‐galactopyranosyl‐(1–2)‐β‐D‐glucuronopyranosyl quillaic add 28‐O‐α‐L‐arabinopyranosyl‐(1–3)‐α‐L‐rhamnopyranosyl‐(1–2)‐[α‐L‐arabinofuranosyl‐(1–3)]‐4‐O‐acetyl‐β‐D‐fucopyranoside (3), 3‐O‐β‐D‐galacto‐pyranosyl‐(1–2)‐[β‐D‐xytopyranosyl‐(1–3)]‐β‐D‐glucurono‐pyranosyl quillaic add 28‐O‐β‐D‐xylopyranosyl‐(1–3)‐α‐L‐rhamnopyranosyl‐(1–2)‐[α‐L‐arabinofuranosyl‐(1–3)]‐4‐O‐acetyl‐β‐D‐fucopyranoside (4), respectively.     

Synthesis and Crystal Structures of Novel Copper(I) Clusters with Bridging Silyl Amide Ligands

Treatment of copper(I) chloride with R₂Si(NLiPh)₂ (R = Me, Ph) in thf led to the formation of the octanuclear cluster compounds [Cu₈{(R₂Si(NPh)₂}₄] [R = Me ( 1 ), Ph ( 2 ).] Compound 1 crystallizes in the tetragonal space group P4/n, with a = 1505.41(5) and c = 1911.32(7) pm. The X‐ray crystal structure determination revealed a cube shaped Cu₈ cluster core with μ₄ bridging Me₂Si(NPh)₂^2– ligands. The copper atoms display an almost linear coordination with Cu–N distances in the range of 191.1(3)–191.4(3) pm. The Cu–Cu distances are 265.7(1)–267.3(1) pm. Compound 2 forms monoclinic crystals, space group P2₁/n, with a = 1461.87(4), b = 2483.77(6), c = 2725.49(8) pm, β = 100.77(1)°. The cluster core of compound 2 consists formally of two mutually perpendicular arranged trigonal prisms, which share a common square face. Like in the case of compound 1 the square faces of the cluster core are capped by μ₄ bridging Ph₂Si(NPh)₂^2– ligands. The copper atoms adopt a nearly linear N–Cu–N coordination with Cu–N distances of 190.0(4)–195.1(4) pm. The Cu–Cu distances are 252.3(1)–305.6(1) pm.     

Sesquiterpenoids of the Sponge Dysidea fragilis of the North-Brittany Sea

The title sponge is shown to contain eight new sesquiterpenoids for which a common, unusual biogenetic origin is postulated. The compounds are shown to be: (–)-(1R*,4R*)-3-(3′-furyl)methyl-2-p-menthen-7-yl acetate ((–)- 8b ); two diols separated as the monoacetates (–)-(1S*,4R*)-3-(3′-furyl)methyl-l-hydroxy-2-p-menthen-7-yl acetate ((–)- 13a ) and the (–)-(1R*,4R*)-epimer (–)- 13b , the two C(4)-epimeric 4-ethoxy-3-(1′(7′),2′-p-menthadien-3′-yl)methyl-2-buten-4-olides ((+)- 14a and (–)- 14b ), (–)-3-(3′-furyl)methyl-7-nor-2-p-menthen-l-one ((–)- 11 ), (–)-(3Z)-1-(3′-furyl)-4,8-dimethylnona-3, 7-dien-2-yl acetate ((–)- 17 ), and (+)-3-(5′,7′-seco-2′(10′)-pinen-7′-yl)methylfuran ((+)- 15 ).     

Formation of 1,1,2,3,3-pentakis(arylthio)-1-propenes from tris(arylthio)cyclopropenyl cations and their conversion into 1,1,2,5,6,6-hexakis(arylthio)-(3E)-1,3,5-hexatriene

The reaction of tetrachlorocyclopropene (1) with arenethiols (2a–e), followed by treatmentwith perchloric acid, gave tris(arylthio)cyclopropenylium perchlorates (3a–c and e), 1,1,2,3,3-pentakis(arylthio)-1-propenes (4a–d), and 2,3,3-tris(arylthio)propenals (5a–d). The structures of tris(phenylthio)cyclopropenylium perchlorate (3a), 1,1,2,3,3-pentakis(phenylthio)-1-propene (4a), and 2,3,3-tris(o-tolylthio)propenal (5b) were analyzed by single-crystal X-ray diffraction studies. The yields depended significantly on the electron-withdrawing property of the substituents of the arenethiols and the molar ratio of 2 to 1. The reaction with 2,6-dimethylbenzenethiol (2e) gave only tris(2,6-dimethylphenylthio)cyclopropenylium perchlorate (3e) without the formation of 4e and 5e. Compounds 5a–d were produced by acid hydrolysis of 4a–d. Pyrolysis of 4a–d gave (3R,4S)-1,1,2,3,4,5,6,6-octakis(arylthio)-1,5-hexadienes (9a–d) and 1,1,2,5,6,6-hexakis(arylthio)-(3E)-1,3,5-hexatrienes (10a–d) together with diaryl disulfides (11a–d). Compound 10a was also produced by photolysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:387–397, 1998     

Phosphorescent self-healing composites containing Re(I) complexes: preparation and properties

Abstract

To obtain self-healing phosphorescent composites, four Re(I) complexes, Re-Ura-a (a?=?1–4) with uracil group were synthesized. The ultraviolet-visible (UV-Vis) absorption spectra of Re-Ura-a (a?=?1–4) are mainly comprised of the π→π* transitions (200–400?nm) and the metal-to-ligand charge transfer transitions (400–450?nm). The photoluminescence (PL) spectra of Re-Ura-a (a?=?1–4) peaking at 576–584?nm possess the biexponential excited-state decay lifetimes (τ) of 0.19–0.43 μs. The PL spectra of Re-Ura-a@PAA (a?=?1–4, PAA?=?polyacrylic acid) gel blocks redshift to ca. 600?nm with τ values of ca. 0.33 μs. The Re-Ura-1(0.6?wt%)@PAA gel blocks could bear maximum stress of 0.191?MPa and maximum strain of 525%, and they could be ca. 40% self-healed in 5?min after being severed. Finally, the energies of the H-bonds between the carboxylic group of PAA and different parts of Re-Ura-1 were theoretically simulated to investigate the intermolecular interactions between Re-Ura-1 and PAA.     

Novel open-chain and cyclic conformationally constrained (R)- and (S)-α,α-disubstituted tyrosine analogues

A series of novel open-chain and cyclic conformationally constrained (R)- and (S)-α,α-disubstituted tyrosine analogues 1a–e were synthesized in good yields and high optical purities (Schemes 1 and 2). The absolute configurations of these tyrosine analogues were unambiguously determined based on the X-ray structures of the precursor diastereoisomeric peptides of type 4 and 5 . Four of these structures are described (Figs. 1–4), showing β-turn type-I geometries for dipeptides 4a, 5b , and 4c and an extended conformation for peptide 5c (Table 3). The conversion of the free amino acids 1a–c into suitably protected building blocks 11a–d and 15d,e for peptide synthesis is discussed (Schemes 3 and 4).     

Synthese von 2H-Isoindol-4,7 -dionen durch photochemische Cycloaddition von 2,3-Diphenyl-2H-azirin an 1,4-Chinone. 38. Mitteilung über Photoreaktionen

2, 3-Diphenyl-2H-azirine ( 1 ) reacts on irradiation with light of wavelength 290–350 nm with 1,4-benzoquinones 3–6 or with 1,4-naphthoquinones 7–9 forming the yellow to red coloured 1,3-diphenyl-2H-isoindole-4, 7-diones 10–13 (33–43% yield) resp. 1, 3-diphenyl-2H-benzo[f]isoindole-4,9-diones 14–16 (33–36% yield) (Scheme 1). The structures of these hitherto unknown products follow from the analytical and spectral data. The probable formation of the isoindole-diones is depicted in Scheme 2. The intermediate benzonitrile-benzylide ( 2 ), which most certainly arises, adds onto the unsubstituted C, C-double bond of the quinones and not onto the C,O-double bonds. On exclusion of atmospheric oxygen there results from 1 and 2-methyl-1, 4-benzoquinone ( 4 ) a product (probably b ) which hardly absorbs in the region 350–450 nm. The latter, with the agency of atmospheric oxygen (but not 4 ), is converted into 5-methyl-1, 3-diphenyl-2H-isoindole-4, 7-dione ( 11 ). The relative slowness of this oxidation (see Fig. 2) enables an almost complete photochemical transformation of the azirine 1 , which only weakly absorbs above 290 nm. Otherwise 11 , which strongly absorbs above 290 nm, would hinder the photolysis of 1 .     

Vier Natrium‐di(arensulfonyl)amide: Lamellare Schichten mit kurzen Zwischenschichtkontakten C–H…O(Nitro), C–H…F–C oder C–I…I–C

Structures of Ionic Di(arenesulfonyl)amides. 3. Four Sodium Di(arenesulfonyl)amides: Lamellar Layers Exhibiting Short C–H…O(nitro), C–H…F–C, or C–I…I–C Interlayer Contacts Low‐temperature X‐ray crystal structures are reported for NaN(SO₂C₆H₄‐4‐X)₂ · n H₂O, where X = NO₂ and n = 3 ( 1 , monoclinic, space group P2₁, Z = 2), X = F and n = 3 ( 2 , monoclinic, P2₁/c, Z = 4), X = F and n = 1 ( 3 , orthorhombic, Pccn, Z = 8), or X = I and n = 1 ( 4 , monoclinic, P2₁/c, Z = 4). The four compounds are examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations, N(SO₂)₂ groups and H₂O molecules and the outer regions are formed by the 4‐substituted phenyl rings of the folded anions. In the two‐dimensional coordination networks, the cations adopt either an octahedral [Na(O–S)₂(OH₂)₄] ( 1 , 2 ) or a distorted monocapped octahedral [NaN(O–S)₄(OH₂)₂] ( 3 , 4 ) environment. Taking into account the differing crystal symmetries within the two pairs of compounds, it is remarkable that the trihydrates 1 / 2 and the monohydrates 3 / 4 each display chemically identical and nearly isometric Na–O or Na–O/N networks. In the crystal packings, parallel layers are connected through weak hydrogen bonds C–H…O(nitro) ( 1 ) or C–H…F ( 2 , 3 ), or through short “type I” I…I contacts ( 4 ). There is good evidence that the strikingly distinct crystal symmetries in the halogenated homologues 3 / 4 are determined by the specific complementarity requirements of the interlayer binding centres.     

Calculation of Some Thermodynamic Properties and Detonation Parameters of 1‐Ethyl‐3‐Methyl‐H‐Imidazolium Perchlorate, [Emim][ClO4], on the Basis of CBS‐4M and CHEETAH Computations Supplemented by VBT Estimates

This paper estimates some thermochemical (in kcal mol^–1) and detonation parameters for the ionic liquid, [emim][ClO₄] and its associated solid in view of its investigation as an energetic material. The thermochemical values estimated, employing CBS‐4M computational methodology and volume‐based thermodynamics (VBT) include: lattice energy, U_POT([emim][ClO₄]) ≈? 123 ± 16 kcal · mol^–1; enthalpy of formation of the gaseous cation, Δ_fH°([emim]⁺, g) = 144.2 kcal · mol^–1 and anion, Δ_fH°([ClO₄]^–, g) = –66.1 kcal · mol^–1; the enthalpy of formation of the solid salt, Δ_fH°([emim][ClO₄],s) ≈? –55 ± 16 kcal · mol^–1 and for the associated ionic liquid, Δ_fH^o([emim][ClO₄],l) = –52 ± 16 kcal · mol^–1 as well as the corresponding Gibbs energy terms: Δ_fG°([emim][ClO₄],s) ≈? +29 ± 16 kcal · mol^–1 and Δ_fG^o([emim][ClO₄],l) = +24 ± 16 kcal · mol^–1 and the associated standard absolute entropies, of the solid [emim][ClO₄], S°₂₉₈([emim][ClO₄],s) = 83 ± 4 cal · K^–1 · mol^–1. The following combustion and detonation parameters are assigned to [emim][ClO₄] in its (ionic) liquid form: specific impulse (I_sp) = 228 s (monopropellant), detonation velocity (V_oD) = 5466 m · s^–1, detonation pressure (p_C–J) = 99 kbar, explosion temperature (T_ex) = 2842 K.     

Design of two series of 1:1 cocrystals involving 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine and carboxylic acids

Two series of a total of ten cocrystals involving 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine with various carboxylic acids have been prepared and characterized by single‐crystal X‐ray diffraction. The pyrimidine unit used for the cocrystals offers two ring N atoms (positions N1 and N3) as proton‐accepting sites. Depending upon the site of protonation, two types of cations are possible [Rajam et al. (2017). Acta Cryst. C 73 , 862–868]. In a parallel arrangement, two series of cocrystals are possible depending upon the hydrogen bonding of the carboxyl group with position N1 or N3. In one series of cocrystals, i.e. 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–3‐bromothiophene‐2‐carboxylic acid (1/1), 1 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–5‐chlorothiophene‐2‐carboxylic acid (1/1), 2 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2,4‐dichlorobenzoic acid (1/1), 3 , and 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2‐aminobenzoic acid (1/1), 4 , the carboxyl hydroxy group (–OH) is hydrogen bonded to position N1 (O—H…N1) of the corresponding pyrimidine unit (single point supramolecular synthon). The inversion‐related stacked pyrimidines are doubly bridged by the carboxyl groups via N—H…O and O—H…N hydrogen bonds to form a large cage‐like tetrameric unit with an R₄²(20) graph‐set ring motif. These tetrameric units are further connected via base pairing through a pair of N—H…N hydrogen bonds, generating R₂²(8) motifs (supramolecular homosynthon). In the other series of cocrystals, i.e. 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–5‐methylthiophene‐2‐carboxylic acid (1/1), 5 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–benzoic acid (1/1), 6 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2‐methylbenzoic acid (1/1), 7 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–3‐methylbenzoic acid (1/1), 8 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–4‐methylbenzoic acid (1/1), 9 , and 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–4‐aminobenzoic acid (1/1), 10 , the carboxyl group interacts with position N3 and the adjacent 4‐amino group of the corresponding pyrimidine ring via O—H…N and N—H…O hydrogen bonds to generate the robust R₂²(8) supramolecular heterosynthon. These heterosynthons are further connected by N—H…N hydrogen‐bond interactions in a linear fashion to form a chain‐like arrangement. In cocrystal 1 , a Br…Br halogen bond is present, in cocrystals 2 and 3 , Cl…Cl halogen bonds are present, and in cocrystals 5 , 6 and 7 , Cl…O halogen bonds are present. In all of the ten cocrystals, π–π stacking interactions are observed.     

Synthesis and characterization of N -(alky(aryl)carbamothioyl)cyclohexanecarboxamide derivatives and their Ni(II) and Cu(II) complexes

N-(R-carbamothioyl)cyclohexanecarboxamides (R: diethyl, di-n-propyl, di-n-butyl, diphenyl and morpholine-4) and their Ni(II) and Cu(II) complexes have been synthesized and characterized by elemental analyses, FT-IR and NMR methods. N-(diethylcarbamothioyl)cyclohexanecarboxamide, HL¹, C₁₂H₂₂N₂OS, crystallizes in the orthorhombic space group P2₁2₁2₁, with Z = 4, and unit cell parameters, a = 6.6925(13) Å, b = 9.0457(18) Å, c = 22.728(5) Å. The conformation of the HL¹ molecule with respect to the thiocarbonyl and carbonyl moieties is twisted, as reflected by the torsion angles O1–C6–N2–C5, C6–N2–C5–N1 and S1–C5–N2–C6 of 1.68°, ?67.47° and 115.50°, respectively. The structure of HL¹ also shows a delocalization of the π electrons of the thiocarbonyl group over the C–N bonds. The ring puckering analysis shows that the cyclohexane ring has a chair conformation. The bis(N-(morpholine-4-carbonothioyl)cyclohexane carboxamido)nickel(II) complex, Ni(L⁵)₂, C₂₄H₃₈N₄NiO₄S₂, crystallizes in the monoclinic space group P2₁/c, with Z = 4, and unit cell parameters, a = 16.919(3) Å, b = 8.3659(17) Å, c = 19.654(4) Å, β = 107.43(3)°. Ni(L⁵)₂ is a cis-complex with a slightly distorted square-planar coordination of the central nickel by two oxygen and two sulfur atoms.     

Synthesis and Antimicrobial Evaluation of Some Novel Pyrido[2,3‐d] Pyrimidine Derivatives and Their Ribofuranosides

2‐Amino‐3‐cyano‐4,6‐disubstituted pyridines 2a–c on treatment with arylisocyanate and arylisothiocyanate afforded 4‐imino‐3,5,7‐trisubstituted pyrido[2,3‐d] pyrimidin‐2(1H)‐ones 3a–c and 4‐imino‐3,5,7‐trisubstituted pyrido[2,3‐d]pyrimidin‐2(1H)‐thiones 4a–c , respectively. The ribofuranosides, namely, 4‐imino‐3,5,7‐trisubstituted‐1‐(2′,3′,5′‐tri‐O‐benzoyl‐β‐d ‐ribofuranosyl) pyrido[2,3‐d]pyrimidin‐2(1H)‐ones 7a–c and 4‐imino‐3,5,7‐trisubstituted‐1‐(2^′,3^′,5^′‐tri‐O‐benzoyl‐β‐D‐ribofuranosyl) pyrido[2,3‐d]pyri‐midin‐2(1H)‐thiones 8a–c , were synthesized by the condensation of trimethylsilyl derivatives of 3a–c and 4a–c with β‐d ‐ribofuranosyl‐1‐acetate‐2,3,5‐tribenzoate. The structure of newly synthesized ribofuranosides and their precursors were established by elemental analyses, IR, ¹H NMR and ¹³C NMR spectroscopy. All the synthesized compounds were screened for their antibacterial and antifungal activities against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Aspergillus flavus.     

3Mg(OH)2·MgSO4·8H2O: A Metastable Phase in the System Mg(OH)2‐MgSO4‐H2O

In the course of investigations relating to magnesia oxysulfate cement the basic magnesium salt hydrate 3Mg(OH)₂ · MgSO₄ · 8H₂O (3–1–8 phase) was found as a metastable phase in the system Mg(OH)₂‐MgSO₄‐H₂O at room temperature (the 5–1–2 phase is the stable phase) and was characterized by thermal analysis, Raman spectroscopy, and X‐ray powder diffraction. The complex crystal structure of the 3–1–8 phase was determined from high resolution laboratory X‐ray powder diffraction data [space group C2/c, Z = 4, a = 7.8956(1) Å, b = 9.8302(2) Å, c = 20.1769(2) Å, β = 96.2147(16)°, and V = 1556.84(4) ų]. In the crystal structure of the 3–1–8 phase, parallel double chains of edge‐linked distorted Mg(OH₂)₂(OH)₄ octahedra run along [–110] and [110] direction forming a pattern of crossed rods. Isolated SO₄ tetrahedra and interstitial water molecules separate the stacks of parallel double chains.     

A Novel Approach to 2,2-Disubstituted 1,2-Dihydro-4-phenylquinolines

The reaction of 2-(1-phenylvinyl)aniline and 4-chloro-2-(1-phenylvinyl)aniline with acetophenone derivatives, 1-(naphthalen-1-yl)ethanone and 1-(furan-2-yl)ethanone in toluene at 110–115° with toluene-4-sulfonic acid as a catalyst leads in good-to-excellent yields to the 2,2-disubstituted 1,2-dihydro-4-phenyl-quinolines 1–18 (Scheme 1, Table). The structure of the new racemic 1,2-dihydroquinolines 1–18 is determined by NMR spectroscopy. A reaction mechanism proceeding via a 6π-electrocyclic rearrangement of 2-(1-phenylvinyl)anils 19 as the key step is proposed for the formation of these compounds (Scheme 1). The scope and limitations of the novel methods are discussed (Scheme 2).     

Design,synthesis, and anticancer activity evaluation of novel aziridine-1,2,3-triazole hybrid derivatives

Some new 1-aryl-4-[(aziridine-1-yl)diaryl-methyl]-5-methyl-1H-1,2,3-triazole derivatives 7j–s were synthesized by the one-pot reaction of diaryl-(1-aryl-5-methyl-1H-1,2,3-triazol-4-yl)methanol compounds 6j–s formed from 1-aryl-5-methyl-1H-1,2,3-triazole-4-carboxylic acid derivatives. The new compounds 7j–s and 6j–s are investigated by ¹H and ¹³C NMR, MS, and IR. The anticancer activity of the synthesis target compounds was evaluated against human leukemia (HL-60) cells and human hepatoma G2 cells. Some of the compounds were highly efficient. The ¹H-NMR signals of the aziridine-ring cis-H/trans-H protons were found to be two group peaks at 1.800–1.884 and 1.183–1.327?ppm.     

Xenicane Diterpenes Revisited: Thermal (E)→(Z) isomerization and conformational motions. A unifying picture

Kinetic and equilibrium studies show that typical xenicanes such as dictyolactone ( 1 ) and 4-hydroxydictyolactone ( 3 ) undergo slow conformation medium-ring flipping between the predominant trans-( 1a or 3a ; Me(20) trans to H–C(3)) and the minor cis-conformers ( 1b or 3b ; Me(20) cis to H–C(3); see Scheme 1). The formation of the latter is inhibited in heterocyclic-ring-opened congeners such as 18-acetoxy-4-hydroxydictyo-19-al ( 7 ). Molecular-mechanics calculations suggest that typical-xenicane cis-conformers are disfavoured by mainly C(4)–C(5) torsional strain. This is confirmed by the observation of two sizably populated cis-and trans-conformers for the unnatural 4-oxoxenicanes 10–12 . Unusually facile thermal (E)→(Z) isomerization of xenicanes 1,3,10–12 , and 7 is also observed (→ 13–17 and 9 , resp.; Scheme 3), reflecting great strain relief in the transition state. Conflicting results in the literature now fit into this scheme which provides a basis for unravelling recognition phenomena with these biologically active systems.     

Polychloroprene. I. Etude de la microstructure par RMN 1H

The microstructure of polychloroprenes was studied by ¹H-NMR at high field (350 MHz). An examination with two solvents, CDCl₃ and C₆D₆, was necessary to show all the addition modes. The complementary information obtained made possible the quantitative determination of head-to-tail, head-to-head, tail-to-tail, trans-1–4, and cis-1–4, 1–2, and 3–4 additions.     

Esterolytic activity of imidazole-containing polymers. Synthesis and characterization of copoly[1-alkyl-4- or 5-vinylimidazole/4(5)-vinylimidazole] and its catalytic activity in the hydrolysis of p-nitrophenyl acetate

The water-soluble monomers, 1-methyl-4-vinylimidazole, 1-methyl-5-vinylimidazole, 1-ethyl-5-vinylimidazole, and 1-propyl-5-vinylimidazole have been synthesized, polymerized, and copolymerized with 4(5)-vinylimidazole. The copolymers were characterized by ¹⁴C-labeling, NMR, pK_a determination and viscosity measurements. The monomer reactivity ratios determined by ¹⁴C counting are r₁ = 1.04; r₂ = 0.94 [M₁ = 4(5)-vinylimidazole, M₂ = 1-methyl-4-vinylimidazole] and r₁ = 1.01; r₂ = 0.86 [M₁ = 4(5)-vinylimidazole, M₂ = 1-methyl-5-vinylimidazole]. The esterolytic activity of the copolymers for the hydrolysis of p-nitrophenyl acetate (PNPA) at pH 7–8 in 28.5% ethanol–water was higher than that of the mixtures of homopolymers. At pH 5–6 the esterolytic activities of the copolymers and the mixtures were similar. The most efficient esterolytic activity for PNPA hydrolysis at pH 7.11 in 28.5% ethanol–water occurred for copolymers containing 75 mole % 4(5)-vinylimidazole and for copolymers containing 1-methyl-4-vinylimidazole rather than 1-methyl-5-vinylimidazole.     

Carbofuran: analytical methods and its determination in natural water samples by flow injection DPA(III)–H2SO4 chemiluminescence

This study proposes, a simple, rapid and sensitive chemiluminescent (CL) method for determination of carbofuran based on diperiodatoargentate(III) (DPA)-sulfuric acid (H₂SO₄) reaction coupled with flow injection (FI) methodology. Under optimum conditions, a linear standard curve is achieved in the range of 0.001–8.0 mg L^–1 (R²= 0.9994 (n = 11) with relative standard deviation (RSD) of 1.4–3.7% (n = 4)), a limit of detection (LOD) 5.0 × 10^–4 mg L^–1 (S/N = 3) and injection throughput 180 h^–1. The proposed method was applied satisfactorily for the analysis of carbofuran in freshwater samples using solid phase extraction (SPE) technique with the recoveries of 94–110% (% RSD = 1.7–3.8, n = 4). A possible CL reaction mechanism has also been discussed briefly.     

Synthesis and Anticancer Activity of Novel Nonfused Bicyclic Thiazolidinone Derivatives

A series of new 2-{4-oxo-2-[(4-oxothiazolidin-2-ylidene)-hydrazono]-thiazolidin-5-yl}-N-arylacetamides ( 4a–e ), 5-(2-oxo-2-aryl-ethyl)-2-[(4-oxothiazolidin-2-ylidene)-hydrazono]-thiazolidine-4-ones ( 5a–d ), 2-(4-oxo-2-[(2-oxothiazolidin-4-ylidene)-hydrazono]-thiazolidin-5-yl)-N-arylacetamides ( 7a–e ), and 5-(2-oxo-2-aryl-ethyl)-2-[(2-oxothiazolidin-4-ylidene)-hydrazono]-thiazolidine-4-ones ( 8a–d ) have been synthesized starting from 2-thioxothiazolidin-4-one and 4-thioxothiazolidin-2-one through a multistep reaction sequence. 2-Thioxothiazolidin-4-one was alkylated via the intermediate formation of the triethylammonium salt 1 by ethyl chloroacetate. Compound 2 and 4-thioxothiazolidin-2-one reacted with thiosemicarbazides to give the 1-(4-thiazolidinone-2-ylidene)-4-R-thiosemicarbazones ( 3a,b ) and 1-(2-thiazolidinone-4-ylidene)thiosemicarbazones ( 6a,b ), respectively. Following [2+3]-cyclization of thiazolidinone-substituted thiosemicarbazones ( 3a,b and 6a,b) with N-arylmaleimides and aroylacrylic acids as equivalents of dielectrophilic synthon [C₂]^{2 +}, novel non-fused bicyclic thiazolidinones ( 4a–e, 5a–d, 7a–e, 8a–d ) were synthesized. The structures of the new compounds ( 4a–e, 5a–d, 7a–e, 8a–d ) were established on the basis of their elemental analysis and ¹H NMR and mass spectral data. Eight of the synthesized compounds were tested, and three of them displayed different levels of antitumor activity. The most efficient antitumor agent—2-{4-oxo-3-furylmethyl-2-[(4-oxothiazolidin-2-ylidene)-hydrazono]-thiazolidin-5-yl}-N-4-chlorophenylacetamide ( 4d ) was found to be active against leukemia, melanoma, lung, colon, CNS, ovarian, renal, prostate, and breast cancer cell lines with mean lgGI₅₀ and lgTGI values of –5.35 and –4.78, respectively.