Jasna Vorkapić-Furač

The Novel 6–(N-Pyrrolyl)purine Acyclic Nucleosides: 1H and 13C NMR and X-ray Structural Study†

Abstract Synthesis of the novel nucleoside analogues containing exocyclic pyrrolo moiety and acyclic side chains attached to the purine ring at N-9 and N-7 is described. The site of alkylation was determined by 1H and 13C NMR on the basis of chemical shifts, C-H coupling constants and connectivity in NOESY and HETCOR spectra. The N-9 substitution of 7 was proved by its X-ray crystallographic analysis. † Part of the paper was presented at the Ninth International Course and Conference on the Interfaces Among Mathematics. Chemistry and Computer Sciences. Dubrovnik, Croatia (1994).

Balance of glucosinolates content under Cd stress in two Brassica species

We designed a pot experiment to study the changes of growth parameters, accumulation of Cd in cabbage and kale, during a prolonged exposure period with two harvests (after 45 and 75 days of plant growth). Simultaneously, we monitored changes of total S and GSL contents in different plant organs. Both Brassica species showed tolerance to Cd, since no obvious symptoms of metal toxicity were displayed and no significantly reduced plant biomass were recorded. Moreover, a trend of root biomass enhancement was noticed. In general, the Cd concentration in roots was higher than in other organs. Data indicate that the transport system from roots to shoots was already saturated after the first growing period, while root continued to accumulate Cd during the second growing period. Regardless of differences in the GSL content between cabbage and kale, both Brassica species had a similar response to Cd exposure, indicating that the Brassicacea plant family could have unique features for the regulation of GSL content in order to balance the roles of GSLs as defence compounds and as S reservoirs. During the first growing period, GSLs in leaves and root could be more involved in ameliorating S deficiency rather than plant defence. After long-term Cd exposure, we found differences between GSL patterns in leaves and root. Furthermore, we found increased total GSL levels in the stem during whole experiment which indicates that stem could serve as a GSLs storage organ under Cd stress. This paper provides new insight into the possible roles of GSL in Cd stress.

Sterically hindered N-aryl pyrroles: chromatographic separation of enantiomers and barriers to racemization

The novel N-aryl-2,5-dimethylpyrrole-3-carbaldehydes (1)–(7) have been synthesized by condensation of hexane-2,5-dione with the appropriate aniline and subsequent Vilsmeier–Haack formylation of the pyrrole ring. Diastereoisomeric association complexes of these racemic pyrroles were studied by 1H n.m.r. spectroscopy chemical shifts and the splittings induced by the optically active auxiliary compound (+)-Eu(hfbc)3. Separation of the enantiomers of (6) was achieved by liquid chromatography on triacetylcellulose. The barrier to partial rotation about the C–N bond in (6) was determined and their lower limits in (2) and (4) were estimated by variable temperature 1H n.m.r. spectroscopy.

Synthesis of some schiff bases of 3-aroyl-6-aryl-4-hydroxy-2H-pyran-2-ones

SummaryThe reaction of 3-aroyl-6-aryl-4-hydroxy-2H-pyran-2-ones (Ar=p-tolyl, 1,1′-biphenyl-4-yl or thienyl) with aniline and substitutedo-phenylenediamine (R=H, CH3 or Cl) yields a series of new Schiff bases2a–f in 51–72% yield. Bromination of1a gave the 5-bromo derivative1c, while the compounds1a,1b,2b,2e, and2f were converted into 2,6-diaryl-4H-pyran-4-ones3a–c. All products have been fully characterized.ZusammenfassungDie Reaktion von 3-Aroyl-6-aryl-4-hydroxy-2H-pyran-2-onen (Ar=p-Tolyl, 1,1′-Biphenyl-4-yl oder Thienyl) mit Anilin und substituierteno-Phenylendiaminen liefert neue Schiffsche Basen2a–f/bd in 51–72% Ausbeute. Bromierung von1a gab das 5-Bromderivate1c, während die Verbindungen1a,1b,2b,2e und2f in 2,6-Diaryl-4H-pyran-4-onen3a–c übergeführt wurden. Alle Produkte wurden voll charakterisiert.

β-Tricarbonyl compounds. I. 2,4-Disubstituted 1,3-cyclopentanediones

SummaryStable enolic isomers of 2-aroyl-4-aracyl-1,3-cyclopentanediones such as3 and4 were prepared by condensation of aryl methyl ketones and diethyl maleate using an excess of sodium ethoxide (Aryl=C6H5, 4-C6H4CH3, 4-C6H4Br and 4-C6H4Cl).ZusammenfassungStabile Enol-Isomere von 2-Aroyl-4-aracyl-1,3-cyclopentandionen wie3 und4 wurden durch Kondensation von Arylmethylketonen und Diethylmaleat mit einem Überschuß von Natriumethoxid dargestellt (Aryl=C6H5, 4-C6H4CH3, 4-C6H4Br und 4-C6H4Cl).

Ionske kapljevine – razvoj i izazovi industrijske primjene

Posljednjih godina sve veći negativni učinci na okoliš i ljude, poput zagađenja zraka, tla i vode te promjena klime na globalnoj razini, posljedica su neprimjerene primjene raznih štetnih tvari koje se izravno ili neizravno primjenjuju u kemijskoj, petrokemijskoj, farmaceutskoj, biotehnološkoj i agrokemijskoj industriji. Primjerice, hlapljiva organska otapala čine gotovo ⁄3 svih industrijskih emisija širom svijeta, pri čemu je većina toksična, zapaljiva i korozivna, dok je njihovo recikliranje i ponovna uporaba povezana s energetski zahtjevnom destilacijom uz znatne gubitke.1 Stoga akademska zajednica pridaje veliku pozornost pronalasku novih, ekološki prihvatljivih i neškodljivih otapala.

N-(o-chlorophenyl)-2,5-dimethyl-pyrrole-3-carbaldehyde

Crystal structure analysis of the title compound, C(13)H(12)ClNO, reveals three crystallographically independent molecules in the asymmetric unit. The main conformational difference between these molecules is the orientation of the phenyl rings with respect to the pyrrole rings. The coplanar arrangement of the aldehyde groups attached to the pyrrole rings influences the pyrrole-ring geometry. The C2-C3 and N1-C5 bonds are noticeably longer than the C4-C5 and N1-C2 bonds. Two independent molecules of the title compound form dimers via intermolecular C-H.O hydrogen bonds [D.A = 3.400 (3) A and D-H.A = 157 degrees ]. The perpendicular orientation of the phenyl and pyrrole rings of one independent molecule and its symmetry-related molecule allows C-H.pi interactions, with an H.centroid distance of 2.85 A and a C-H.pi angle of 155 degrees. The distances between the H atom and the pyrrole-ring atoms indicate that the C-H bond points towards one of the bonds in the pyrrole ring.

SYNTHESIS OF SOME 2H-PYRONE AND FERROCENE CONTAINING HETEROCYCLIC SYSTEMS

Reactions of ethyl 2-hydroxy-4-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-4-oxobut-2-enoate (1) with o-phenylenediamine, 3, 4-dimethyl- or 3, 4-dichloro-o-phenylenediamine gave mixtures of the corresponding 3-[2-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-2-oxoethylidene]-1, 2, 3, 4-tetrahydroquinoxa-lin-2-ones (2), ethyl 4-(o-aminophenylimino)-2-hydroxy-4-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-but-2-enoate (3), ethyl 4-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-5H-1, 5-benzodiazepine-2-carboxylates (4), and ethyl 2-hydroxy-3-[3-methyl-1-oxo-1H, 5H-pyrano[4, 3-b][1, 5]benzodiazepin-11-yl]prop-2-enoates (5). By the action of 3-amino-1-phenyl-2-pyrazolin-5-one on 1 ethyl 2-phenyl-4-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-3-oxo-3-pyrazolino[3, 4-b]pyridine-6-carboxylate (6) was obtained. Reactions of ethyl 4-ferro-cenyl-1, 4-dioxobutanoate (8) and o-phenylenediamine gave a mixture of 3-(2-ferrocenyl-2-oxoethylidene)-1, 2, 3, 4-tetrahydro-quinoxalin-2-one (9) and ethyl 4-ferrocenyl-1, 5-benzodiazepine-2-carboxylate (10).

Reduction mechanism of 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium iodide in an acidic medium

The reduction mechanism of the selected oxime, 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium iodide (HS10), has been studied by normal pulse polarography (NPP) from a Britton—Robinson buffer of pH 2.6, predominantly on a static mercury drop electrode (SMDE). At pH 2.6, 99% of HS10 is present in the undissociated hydrophobic form. The limiting reduction current is diffusion controlled (diffusion coefficient D = 1.5 × 10 −6 cm2/s; half-wave potential E12 = −0.355 V vs. Ag/AgCl/KCl(sat) reference electrode). The NPP wave of HS10 at pH 2.6 has the characteristic features of a reduction complicated by reactant adsorption. The reduction process is totally irreversible; the average an = 0.975. Considering the uptake of 4e− during the reductive cleavage of the azomethine group (CN) the estimated cathodic transfer coefficient a = 0.234. During the prepulse period t0 the reactant adsorbs at the mercury electrode, following the linear Henry type of isotherm. For 1.01, 4.05 and 8.10 × 10−5 mol 1−1 bulk concentrations of HS10, the surface excesses. Γ0 on SMDE at t = t0 are 0.5, 2.1 and 5.8 × 10−11 mol cm−2 respectively. For the same concentrations of HS10, according to the Henry isotherm the adsorption constant K has been calculated as 4.9, 5.2 and 7.2 × 10−4 cm, which indicates weak reactant adsorption during the pre-pulse period t0.