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Base Analogues (base + analogue)

Distribution by Scientific Domains
Chemistry83%

Selected Abstracts

The Synthesis and Characterization of all Diastereomers of a Linear Symmetrically Fused Tris-Tröger's Base Analogue: New Chiral Cleft Compounds

CHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006
Josep Artacho
Abstract The synthesis and characterization of all diastereomers of a linear symmetrically fused tris-Tröger's base analogue are described. The diastereomers are unambiguously assigned as syn,anti1,a, anti,anti1,b, and syn,syn1,c isomers, by using X-ray diffraction analysis and NMR spectroscopy. For the first time, the anti,anti and the syn,syn diastereomers of a linear symmetrically fused tris-Tröger's base analogue have been synthesized. Molecules 1,a and 1,c are new cleft compounds and analysis of compound 1,a in the solid state shows inclusion of one molecule of CH2Cl2 in the larger aromatic cleft, whereas in isomer 1,c disordered solvent molecules are trapped in the extended aromatic cleft. Furthermore, in the solid state, isomer 1,c forms infinite open channels along one of the crystallographic axes and perpendicular to this axis there are infinitely extending "wedged-ravines". Importantly, each of the diastereomers 1,a,c is resistant to inversion at the stereogenic nitrogen atoms under strongly and weakly acidic conditions in the range from room temperature (RT) to 95,°C. This observed configurational stability at the stereogenic nitrogens of 1,a,c is unique for analogues of Tröger's base in general to date. Finally, the ratio of cleft compounds 1,a and 1,c significantly increased relative to cavity compound 1,b when ammonium chloride was used as an additive in the Tröger's base condensation to 1,a,c suggesting a templating effect of the ammonium ion. [source]

Recent Developments in Synthetic Chemistry, Chiral Separations, and Applications of Tröger's Base Analogues

HELVETICA CHIMICA ACTA, Issue 3 2009
Sergey Sergeyev
Abstract Tröger's base is a well-known chiral molecule with a few unusual structural features. The chemistry of Tröger's base analogues has been greatly developed over the last 20 years, and numerous interesting applications in supramolecular chemistry and in molecular recognition have emerged. This Review gives a short overview of the chemistry of Tröger's base and its analogues, with particular focus on recent achievements in synthesis, enantiomer separations, and applications. [source]

The Synthesis and Characterization of all Diastereomers of a Linear Symmetrically Fused Tris-Tröger's Base Analogue: New Chiral Cleft Compounds

CHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006
Josep Artacho
Abstract The synthesis and characterization of all diastereomers of a linear symmetrically fused tris-Tröger's base analogue are described. The diastereomers are unambiguously assigned as syn,anti1,a, anti,anti1,b, and syn,syn1,c isomers, by using X-ray diffraction analysis and NMR spectroscopy. For the first time, the anti,anti and the syn,syn diastereomers of a linear symmetrically fused tris-Tröger's base analogue have been synthesized. Molecules 1,a and 1,c are new cleft compounds and analysis of compound 1,a in the solid state shows inclusion of one molecule of CH2Cl2 in the larger aromatic cleft, whereas in isomer 1,c disordered solvent molecules are trapped in the extended aromatic cleft. Furthermore, in the solid state, isomer 1,c forms infinite open channels along one of the crystallographic axes and perpendicular to this axis there are infinitely extending "wedged-ravines". Importantly, each of the diastereomers 1,a,c is resistant to inversion at the stereogenic nitrogen atoms under strongly and weakly acidic conditions in the range from room temperature (RT) to 95,°C. This observed configurational stability at the stereogenic nitrogens of 1,a,c is unique for analogues of Tröger's base in general to date. Finally, the ratio of cleft compounds 1,a and 1,c significantly increased relative to cavity compound 1,b when ammonium chloride was used as an additive in the Tröger's base condensation to 1,a,c suggesting a templating effect of the ammonium ion. [source]

Introduction of Aromatic and Heteroaromatic Groups in the 2- and 8-Positions of the Tröger's Base Core by Suzuki, Stille and Negishi Cross-Coupling Reactions , A Comparative Study

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2005
Carlos Solano
Abstract A comparative study on the bis(functionalization) of the Tröger's base core by aromatic and heteroaromatic groups using palladium-catalyzed cross-coupling reactions is presented. Three different reactions, the Suzuki, Stille, and Negishi couplings, were investigated using Tröger's base analogues equally substituted in the 2,8-positions with (HO)2B, Bu3Sn and ZnCl groups, respectively, as the metallated component. Six aryl halides with different electronic and steric properties were employed as coupling partners. The presence of the bulky and electron-rich phosphane P(tBu)3 as co-catalyst was found to play an important role. In addition, the palladium source, [Pd(PPh3)4] or [Pd2(dba)3], was also found to be an important factor for the yield of the reactions. The Suzuki coupling was found to be the best method in general, giving excellent yields for most aryl halides, whereas the Stille and Negishi couplings gave moderate to good yields. Finally, the crystal structures of the 4-nitrophenyl- and the 2-pyridyl-appended analogues of Tröger's base, 7d and 7f, are presented in the Supporting Information. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Recent Developments in Synthetic Chemistry, Chiral Separations, and Applications of Tröger's Base Analogues

HELVETICA CHIMICA ACTA, Issue 3 2009
Sergey Sergeyev
Abstract Tröger's base is a well-known chiral molecule with a few unusual structural features. The chemistry of Tröger's base analogues has been greatly developed over the last 20 years, and numerous interesting applications in supramolecular chemistry and in molecular recognition have emerged. This Review gives a short overview of the chemistry of Tröger's base and its analogues, with particular focus on recent achievements in synthesis, enantiomer separations, and applications. [source]

Production of clastogenic DNA precursors by the nucleotide metabolism in Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 1 2010
Brian Budke
Summary RdgB is a bacterial dNTPase with a strong in vitro preference for non-canonical DNA precursors dHapTP, dXTP and dITP that contain deaminated or aminogroup-modified purines. Utilization of these nucleotides by replisomes in rdgB mutants of Escherichia coli produces modified DNA, on which EndoV nicking near the base analogues initiates excision repair. Some EndoV-initiated excision events cause chromosomal fragmentation, which becomes inhibitory if recombinational repair is also inactivated (the rdgB recA co-inhibition). To reveal the sources and the identities of the non-canonical DNA precursors, intercepted by RdgB in E. coli, we characterized 17 suppressors of the rdgB recA co-inhibition. Ten suppressors affect genes of the RNA/DNA precursor metabolism, identifying the source of non-canonical DNA precursors. Comparing chromosomal fragmentation with the density of EndoV-recognized DNA modifications distinguishes three mechanisms of suppression: (i) reduction of the non-canonical dNTP production, (ii) inhibition of the base analogue excision from DNA and (iii) enhancement of the cell tolerance to chromosomal fragmentation. The suppressor analysis suggests IMP as the key intermediate in the synthesis of the clastogenic DNA precursor, most likely dITP. [source]