Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

5 Polish Journal of Chemistry

Znaleziono wyników: 5

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Five-Membered Heterocycles. Part V. Impact of Heteroatoms on Aromaticity of Five-Membered Heterocycles

100%

Mrozek A. , Karolak-Wojciechowska J.

2007

tom Vol. 81, nr 5-6

721-730

The aromaticity (in the form ofHOMAindex) of various five-membered heterorings systems and their bicyclic derivatives containing N, S, O, and P were studied on the basis of statistical data from Cambridge Structural Database (CSD). The calculations of HOMA were done for pyrroles, furans, thiophenes, phospholes, imidazoles, oxazoles, thiazoles, phosphazoles as well as for 6 + 5 fused systems: benzimidazoles, benzoxazoles, benzothiazoles, and benzophosphazoles. Detailed analysis showed that relationship between classical aromaticity and electronegativity of heteroatom is described by squared equation. An optimal value of electronegativity is about 2.9 (Pauling’s scale) for which aromaticity of heterorings reaches the highest level. For fused systems, the presence of benzene ring causes the evident increasing of average value of HOMA indices.

Molecular structure of 5-chloro-2-[p-t-butylphenyl]benzoxazole : Relation between structure and antimicrobial activity of 2,5-disubstituted benzoxazoles

80%

Mrozek A. , Trzeźwińska H. , Karolak-Wojciechowska J.

1999

tom vol. 73 nr 4

625-633

As part of our investigation on antimicrobial agents, the structure of 5-chloro-2[p-t-butylophenyl]benzoxazole is reported: C17h16ClNO, mol.mass 285.77, monoclinic, space group: C2/c; a=32.164(6) A, b=6.756(1) A, c=13.710(3) A; b=92.73(3)0, V=2975.8(10) A3; d=1.276 g cm-3; Z=8; F(000)=1200; m(CuKa)=2.219 mm-1. Final R=0.0658 for 2621 reflections with F>4s(F). Final atomic coordinates for this 2,5-disubstitued benzoxazole were used as a starting point in molecular modeling of remaining 32 derivatives eearched as antimicrobial agents. Electronic parameters calculated with quantum chemistry methods and classical Hansch's constants were applied in searching for structure-activity correlation. It was established that geometrical parameters (area and volume) and LUMO energy values seem to be most important for the activity.

Structure and activity studies of glycine receptor ligands : Part 4. N-[(7-arylalkyl, 7-aryloxyalkyl)-8-theophyllyl]-glycines

80%

Drabczyńska A. , Karolak-Wojciechowska J. , Kieć-Kononowicz K.

1999

tom vol. 73 nr 5

783-792

Preparation of N-[(7-arylalkyl, 7-aryloxyalkyl)-8-theophyllyl]-glycines by condensation of 8-bromo-theophylline with arylalkyl- and aryloxyalkylbromides and aminolysis with glycine is described. The structure of one of the obtained glycine derivatives was confirmed by X-ray analysis. A comparison of the glycine receptor binding model (molecule L-689,560) and the 3-D structure of that molecule indicates serious differences in molecule shape, explaining their inactivity.

Crystal and Molecular Structure of (-)-(S)- and (+)-(R)-Bromofosfamide

80%

Karolak-Wojciechowska J. , Wieczorek M. , Grynkiewicz G. , Kutner A.

1999

tom Vol. 73, nr 11

1877-1885

The crystal and molecular structures of (-)-(S)- and (+)-(R)-bromofosfamide were determined as a part of our research on therapeutically useful oxazaphosphorines. Both compounds crystallized in strictly enantiotropic crystals. Both sompound undergo partial decomposition during diffractometric exposition with emission of free bromine.

Synthesis of 1-aminoalkanephosphonous acids bearing furan moiety and its stereochemical aspect [1]

71%

Grabowski A. , Lewkowski J. , Nazarski R. , Skowroński R. , Karolak-Wojciechowska J.

1999

tom vol. 73 nr 2

307-311

A series of variously N-substitued (2-furyl)aminomethylanephosphonous acids was synthesized in fair yields. The synthesis of optically pure (S0-(2-furyl)-(R )-N-a-methylbenzylaminomethanephosphonous acid is also presented.