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001-es BibID:	BIBFORM001196
Első szerző:	Kerti Gábor (vegyész)
Cím:	Enantioselective synthesis of 3-methylisochromans and determination of their absolute configurations by circular dichroism / Gábor Kerti, Tibor Kurtán, Tünde-Zita Illyés, Katalin E. Kövér, Sándor Sólyom, Gennaro Pescitelli, Naoko Fujioka, Nina Berova, Sándor Antus
Dátum:	2007
Megjegyzések:	Seven (S)-3-methylisochromans with different substitution patterns on their aromatic rings, and hence with different directions of their sum electric transition moments, were synthesized by ring-closure of optically active (S)-1-arylpropan-2-ol derivatives. The (S)-1-arylpropan-2-ols were obtained by kinetic resolution and their absolute configurations were determined with the aid of a zinc porphyrin tweezer and by Mosher£s method. A systematic CD study of substituted isochroman derivatives revealed that, unlike in the cases of chiral tetralin and 2,3-dihydrobenzo[b]furan chromophores, the presence of achiral substituents of large spectroscopic moment (e.g., OMe) on the aromatic ring does not change the helicity rule of the Øunsubstitutedð isochroman chromophore: (P)/(M) helicity of the isochroman heteroring resulted in positive/negative 1Lb band Cotton effects (CE) regardless of the nature(s) and position(s) of the substituent(s). (S)-3-Methylisochromans were oxidized at C-1, allowing access to the corresponding dihydroisocoumarins, in which positive CE of the n-?* transitions were correlated with (P) helicity and (S) absolute configuration. On DDQ-assisted oxidation, two trans-1-methoxy-3-methylisochroman derivatives were prepared and used to study the effect of the axial benzylic C-1 methoxy group on the conformation of the heteroring and the 1Lb band CE.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban chirality configuration determination kinetic resolution
Megjelenés:	European Journal of Organic Chemistry. - 2 (2007), p. 296-305. -
További szerzők:	Kövér Katalin, E. (1956-2023) (vegyész) Sólyom Sándor Pescitelli, Gennaro (1972-) (vegyész) Fujioka, Naoko Berova, Nina Kurtán Tibor (1973-) (vegyész, angol szakfordító) Illyés Tünde Zita (1970-) (kémia-fizika szakos tanár) Antus Sándor (1944-2022) (vegyészmérnök)
Internet cím:	DOI elektronikus változat elektronikus változat
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001-es BibID:	BIBFORM009001
Első szerző:	Kurtán Tibor (vegyész, angol szakfordító)
Cím:	Chiral recognition by CD-sensitive dimeric zinc porphyrin host. 2. Structural studies of host-guest complexes with chrial alcohol and monoamine conjugates / Tibor Kurtán, Nasri Nesnas, Frank E. Koehn, Yuan-Qiang Li, Koji Nakanishi, Nina Berova
Dátum:	2001
Megjegyzések:	A structural study of complexes formed between a dimeric zinc porphyrin tweezer (host) and chiral monoalcohols and monoamines derivatized by a bidentate carrier molecule (guest) confirmed that their CD couplets arise from the preferred porphyrin helicity of 1:1 host-guest complexes. NMR experiments and molecular modeling of selected tweezer complexes revealed that the preferred conformation is the one in which the L (larger) group protrudes from the porphyrin sandwich; this preferred helicity of the complex determines the CD of the complexes. It was found that the porphyrin ring-current induced 1H chemical shifts and molecular modeling studies of the complex lead to the assignments of relative steric size of the L (large)/M (medium) substituents attached to the stereogenic center. The assignments, in turn, are correlated with the sign of the CD exciton couplet that establishes the absolute configuration at the stereogenic center. Variabletemperature NMR experiments proved that the observed increase in CD amplitude at lower temperatures derives from conformational changes in the preferred offset geometry between two porphyrin rings.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Journal of American Chemical Society. - 123 : 25 (2001), p. 5974-5982. -
További szerzők:	Nesnas, Nasri Koehn, Frank E. Li, Yuan-Qiang Nakanishi, Koji Berova, Nina
Internet cím:	elektronikus változat
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001-es BibID:	BIBFORM009002
Első szerző:	Kurtán Tibor (vegyész, angol szakfordító)
Cím:	Chiral recognition by CD-sensitive dimeric zinc porphyrin host. 1. Chiroptical protocol for absolute configurational assignments of monoalcohols and primary monoamines / Tibor Kurtán, Nasri Nesnas, Yuan-Qiang Li, Xuefei Huang, Koji Nakanishi, Nina Berova
Dátum:	2001
Megjegyzések:	A general microscale protocol for the determination of absolute configurations of primary amino groups or secondary hydroxyl groups linked to a single stereogenic center is described. The chiral substrates are linked to the achiral trifunctional bidentate carrier molecule (3-aminopropylamino)acetic acid (1, H2NCH2-CH2CH2NHCH2COOH) and the resultant conjugates are then complexed with dimeric zinc porphyrin host 2 giving rise to 1:1 host/guest sandwiched complexes. These complexes exhibit exciton-coupled bisignate CD spectra due to stereodifferentiation leading to preferred porphyrin helicity. Since the chiral sense of twist between the two porphyrins in the complex is dictated by the stereogenic center of the substrate, the sign of the couplet determines the absolute configuration at this center. The twist of the porphyrin tweezer in the complex can be predicted from the relative steric sizes of the groups flanking the stereogenic center, such that the bulkier group protrudes from the complex sandwich. In certain alpha -hydroxy esters and alpha-amino esters, electronic factors and hydrogen bonding govern the preferred conformation of the complex, and hence the CD spectra.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Journal of American Chemical Society. - 123 : 25 (2001), p. 5962-5973. -
További szerzők:	Nesnas, Nasri Li, Yuan-Qiang Huang, Xuefei Nakanishi, Koji Berova, Nina
Internet cím:	DOI elektronikus változat
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