Search PubMed⌕ Search

Biomedical subjects

I Leban

Publications and source records attributed to I Leban.

7 recordsLinked to original sources
PubMed2001

Influence of chirality of the preceding acyl moiety on the cis/trans ratio of the proline peptide bond.

We report that the cis/trans ratio of the proline peptide bond can be strongly influenced by the chirality of the acyl residue preceding proline. Acyl moieties derived from (2S)-2,6-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid (8) and (2R)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoic acid (5) in acyl-Pro molecules influence isomerization of the proline peptide bond constraining the omega dihedral angle to the trans orientation. Structures of benzyl (2S)-1-([(2S)-2,6-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl]carbonyl)-2-pyrrolidinecarboxylate (3) derived from 2D (1)H NMR conformational analysis and crystallographic data exhibit only the trans conformation of proline peptide bond. On the other hand the diastereomer 4, which contains an (R) acyl moiety, exhibits two sets of signals in (1)H NMR spectra. The signals were assigned to trans (72%) and cis (28%) conformers. Crystallographic analysis of 4 showed that only the cis conformation is present in the crystalline state. The (1)H NMR chemical shift pattern of three sets of signals observed in 2 was observed also in benzyl (2S)-1-[(2R/S)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoyl]-2-pyrrolidinecarboxylate. (R)-Carboxylic acid 5, after coupling with (S)-ProOBn, yielded benzyl (2S)-1-[(2R)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoyl]-2-pyrrolidinecarboxylate (6), which in DMSO-d(6) exhibited only the trans conformation of the proline peptide bond. These results suggest that in these particular cases acyl-Pro peptide bond isomerization is strongly influenced by the stereochemistry of the acyl residue preceding proline. (2S)-2,6-Dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid (8) and (2R)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoic acid (5) are promising chiral peptidomimetic building blocks that can be used as acyl moieties to force the proline peptide bond into the trans conformation in a variety of acyl-Pro molecules.

Crystallography, X-Ray↗
PubMed2001

Two dimeric CuII benzoate derivatives solvated with acetonitrile.

The title compounds, tetrakis(micro-benzoato-O:O')bis(2,6-diaminopyridine)-1kappaN,2kappaN-dicopper(II)-acetonitrile (1/2), [Cu(2)(C(7)H(5)O(2))(4)(C(5)H(7)N(3))(2)].2C(2)H(3)N, (I), and bis(acetonitrile)-1kappaN,2kappaN-tetrakis(micro-benzoato-O:O')dicopper(II)-acetonitrile (1/1.5), [Cu(2)(C(7)H(5)O(2))(4)(C(2)H(3)N)(2)].1.5C(2)H(3)N, (II), crystallize as acetonitrile solvates exhibiting different stability. They have similar molecular structures with discrete dimeric units located at crystallographic inversion centres. The copper ions are bridged by four benzoate groups and neutral N-donor ligands, viz. 2,6-diaminopyridine in (I) and acetonitrile in (II), are coordinated at apical positions. The diverse stability is probably due to hydrogen-bond interactions of the solvated acetonitrile molecules with neighbouring dimers in compound (I).

Journal Article↗
PubMed2000

Methyl 1-

Explore the source record for details and available documents.

Journal Article↗
PubMed2000

From alpha-carbamoyl-alpha-cyanooxiranes to 3-halogenopyruvamides.

The crystal structures of the first stable alpha-diol from the alpha-halogenopyruvamide series, 3-chloro-2, 2-dihydroxy-3-phenylpropanamide, C(9)H(10)ClNO(3), and three products [3-(4-chlorophenyl)-2-cyano-2,3-epoxypropanamide, C(10)H(7)ClN(2)O(2), 3-bromo-2-cyano-2-hydroxy-3-p-tolylpropanamide, C(11)H(11)BrN(2)O(2), 3-bromo-2-oxo-3-p-tolylpropanamide, C(10)H(10)BrNO(2)] obtained during the systematic synthesis of alpha-halogenopyruvamides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups.

Crystallography, X-Ray↗
PubMed1997

Synthesis, crystal structure, and characterization of two metal-quinolone compounds.

Two novel metal-quinolone compounds have been synthesized and characterized by analytical, spectroscopic, and X-ray diffraction methods. The crystal structure of both, (erxH2) [FeCl4]Cl and (kinoH2)[CuCl4]. H2O, is presented and discussed (erxH2 = doubly protonated form of enrofloxacin, kinoH2 = doubly protonated form of the second quinolone). In both compounds, the hydrogen atom is bonded between the 4-keto oxygen O(1) and carboxylic oxygen O(11), thus preventing the bonding of the metal to this part of the molecule. Antimicrobial activities of metal-quinolone compounds were tested against different microorganisms.

Anti-Bacterial Agents↗
PubMed1997

Crystal structure and characterization of the bismuth(III) compound with quinolone family member (ciprofloxacin). Antibacterial study.

Two bismuth(III) compounds of ciprofloxacin (cf) were synthesized. The crystal structure of one--(cfH2) (cfH) [BiCl6].2H2O (cfH2 = doubly protonated molecule of cf, cfH = protonated molecule of cf)--is presented and discussed. The compound crystallizes in the monoclinic space group P 21/c with a = 17.758(4), b = 7.600(10), c = 31.908(6) A, beta = 101.03(2)0, Z = 4. The charge of the isolated hexachlorobismuthate(III) anions is compensated with protonated of molecules (ionic interactions). One of the cf molecules is protonated at carbonyl oxygen O(1) and nitrogen N(24) of the piperazine residue, and the other at N(24) only. Two water molecules participate in the hydrogen bond network. Antimicrobial activity of this compound was tested against different microorganisms. The results of TG and FT-IR measurements are also included.

Anti-Infective Agents↗