Barbara Balázs

Synthesis of chiral 1,3-calix[4](crown-6) ethers as potential mediators for asymmetric recognition processes

Abstract Novel chromogenic 1,3-calix[4](crown-6) derivatives comprised of 1,1′-binaphthyl-, methyl-α- d -glucoside-and d -mannitol moieties in the crown ether ring have been synthesized. UV–vis spectroscopic measurements of the 2,4-dinitrophenylazo chromogenic molecules indicated noticeable chiral discrimination associated with coloration towards primary amine enantiomers.

Isomer-dependent daunomycin release and in vitro antitumour effect of cis-aconityl-daunomycin

Two isomers of cis-aconytil-daunomycin (cAD) were isolated after the reaction of daunomycin with cis-aconitic-anhydride. The structure of the isomers was identified by MS-spectroscopy and 1H and 13C NMR experiments. In contrast with the assumptions described earlier, our results show that the two isomers belong to the cis- and trans-isomers of the alpha-monoamide of cis-aconityl-daunomycin, respectively. We found that the pH dependent daunomycin release is different for the two isomers. Comparative analysis of the in vitro antitumour effect of the isomers on c26 colon carcinoma and on MDA-MB 435P human breast carcinoma cell lines showed that cAD-1 is more potent than cAD-2, but the extent of differences is tumour cell dependent. The results of this study might be appreciated in the light of the use of acid-labile spacer for the design and preparation of protein/peptide conjugates of drugs by indicating that isomers could possess markedly different biological activity.

Quercetin 3,3′,4′-tri-O-β-D-glucopyranosides from leaves of Eruca sativa (Mill.)

Abstract Three new quercetin 3,3′,4′-tri- O -β- d -glucopyranosides isolated from leaves of Eruca sativa (Mill.) were identified as quercetin 3,3′,4′-tri- O -β- d -glucopyranoside, quercetin 3′-(6-sinapoyl- O -β- d -glucopyranosyl)-3,4′-di- O -β- d -glucopyranoside, and quercetin 3-(2-sinapoyl -O -β- d -glucopyranosyl)-3′-(6-sinapoyl- O -β- d -glucopyranosyl)-4′- O -β- d -glucopyranoside. The structures were established by one- and two-dimensional 1 H and 13 C NMR spectra as well as by ESI MS/MS spectra 3

Further dihydrochalcones from Crotolaria ramosissima

Two new dihydrochalcones, crotaramin (2) and crotin (3), have been isolated from the Indian plant Crotolaria ramosissima. Their structures have been elucidated by extensive one- and two-dimensional NMR spectroscopy including HMBC and NOESY.

Synthesis and Conformational Analysis of Dicationic N,N′‐Bridged Bis(benzimidazolium) and Bis(imidazolium) Macrocycles

Two-step alkylations of benzimidazole, 2-methylbenzimidazole, and imidazole at their nitrogen atoms with various bifunctional alkylating agents have afforded a series of 16-membered quaternary azacyclophanes. Of these macrocycles, those bearing methyl or methoxy groups on the azole or at the aromatic bridges have been found to exist as mixtures of conformers. In some cases, the structures of the conformers have been determined by NMR methods and X-ray crystallography, and have been correlated with the results of a computer-aided conformational search.

Iridoid and lignan glycosides from Citharexylum spinosum L.

From the aerial parts of Citharexylum spinosum L., one new iridoid glucoside, the 7-β-O-acetate (1) of lamiide, along with four known iridoid glucosides, lamiide (2), lamiidoside (3), duranterectoside C (4), 8-epiloganin (5) and one known lignan glucoside (+)-lyonirenisol-3a-O-β-D-glucopyranoside (6) were isolated. The compound structures were established by one- and two-dimensional 1H- and 13C-NMR as well as by ESI-MS spectra.

Synthesis and optical investigation of chromogenic 1,3-calix[4]crowns

Chromogenic 1,3-calix[4](crown-5 and -6) ethers containing azophenol and indophenol signalling groups were synthesized and their optical recognition toward alkali and alkaline earth metal cations was investigated by UV–visible spectrophotometry. A calcium ion preference was found to be characteristic of most ligands. A calix[4]crown-5 indolo-spiropyran derivative was also prepared to study the photoisomerization equilibrium of the spiropyran–merocyanine system.

Studies on inclusion complexes of calix[4]arenes capped by diamide bridges with small organic molecules

The inclusion of small neutral organic guests (acetonitrile, toluene, pyrazine, butylamine, nitromethane) by cyclic calix[4]arene diamide receptors was studied by 1H NMR spectroscopy. The binding constants determined by 1H NMR titration, and the results obtained by T1 relaxation measurements and DOSY confirm the importance of the acidity of the CH bond of the guests and highlight the role of steric interactions including conformational properties of the receptors in the recognition process. Copyright

Structure Determination of Zinc Complexes of Iminodiacetamide Ionophores in Solution and in the Solid State

It is shown by extensive NMRinvestigation that hexa-coordinatedZn2+-complexes containing two tridentateiminodiacetamide ligands adopt a solutionconformation with two different kinds ofZn–O bonds possessing a center ofinversion. In contrast, the complexmolecules are chiral in the solid state asdetermined by CP-MAS 13C NMR spectroscopy.