Selective enhancement of (6-4) photoproduct formation in dithymine dinucleotides driven by specific sugar puckering.

Four dinucleotide analogs of thymidylyl(3'-5')thymidine (TpT) have been designed and synthesized with a view to increase the selectivity, with respect to CPD, of efficient UV-induced (6-4) photoproduct formation. The deoxyribose residues of these analogs have been modified to increase north and south conformer populations at 5'- and 3'-ends, respectively. Dinucleotides whose 5'-end north population exceeds ca. 60% and whose 3'-end population is almost completely south display a three-fold selective enhancement in (6-4) adduct production when exposed to UV radiation, compared to TpT. These experimental results undoubtedly provide robust foundations for studying the singular ground-state proreactive species involved in the (6-4) photoproduct formation mechanism.

SN- and NS-puckered sugar conformers are precursors of the (6-4) photoproduct in thymine dinucleotide.

Some amount of furanose in a southern conformation, possibly in both, but certainly in one of the two adjacent nucleotides of a dipyrimidine site, is necessary for (6-4) photoproduct formation in oligonucleotides. To explore the necessity, role, and most favorable location of each South sugar conformer in the formation of the (6-4) adduct in the thymine dinucleotide TpT, the photochemical behavior of two synthetic analogues, in which the South sugar conformation is prohibited for one of their two sugars, has been examined. Herein, we experimentally demonstrate that the presence of one sugar presenting some amount of South puckering, at any of the extremities, is sufficient to trigger (6-4) adduct formation. Nonetheless, the photochemical behavior of the dinucleotide with a South-puckered conformation at the 5'-end, mimics more closely that of TpT. In addition, using the 5' North 3' South-dilocked dinucleotide, we demonstrate that the flexibility of the South pucker at the 3'-end has little influence on the (6-4) adduct formation.

Small Molecule Mixture Analysis by Heteronuclear NMR under Spin Diffusion Conditions in Viscous DMSO-Water Solvent.

Spin diffusion in NMR occurs for small- and medium-sized molecules when their tumbling rate reduces in solution so that magnetization exchange by longitudinal cross relaxation becomes highly efficient. Composite DMSO-water viscous solvents were used for the first time to access the individual NMR spectra of a mixture components in spin diffusion conditions. The easy handling and high dissolution power of [D6 ]DMSO/H2 O offers a wide range of potential applications for polar and moderately apolar mixture analysis. In addition to 2D 1 H-1 H NOESY and 1 H-13 C HSQC-NOESY, 1 H-15 N HSQC-NOESY, 1D and 2D 1 H-19 F heteronuclear NOESY (HOESY) experiments were set up to offer new ways to individualize molecules within a mixture. This article reports the analysis of a polar mixture of four dipeptides dissolved in [D6 ]DMSO/H2 O (7:3 v/v) and that of a medium-polarity fluorinated dinucleotide dissolved in [D6 ]DMSO/H2 O (8:2 v/v) by means of spin diffusion in NOESY, HOESY, and HSQC-NOESY experiments.

Kinetic target-guided synthesis in drug discovery and chemical biology: a comprehensive facts and figures survey.

For the last 15 years, kinetic target-guided syntheses, including in situ click chemistry, have been used as alternative methods to find ligands to therapeutically relevant proteins. In this review, a comprehensive survey of biological targets used in kinetic target-guided synthesis covers historical and recent examples. The chemical reactions employed and practical aspects, including controls, library sizes and product detection, are presented. A particular focus is on the reagents and warhead selection and design with a critical overview of the challenges encountered. As protein supply remains a key success factor, it appears that increased efforts should be taken toward miniaturization in order to expand the scope of this strategy and qualify it as a fully fledged drug discovery tool.

Synthesis and antimycobacterial activity of a series of ferrocenyl derivatives.

In this work we reported the synthesis and evaluation of Mycobacterium tuberculosis activities in vitro of a series of twenty five ferrocenyl derivatives: ferrocenyl amides derived from nicotinamide and pyrazinamide, ferrocenyl pyridinyl, quinolyl and acridinylhydrazones. In particular ferrocenyl acylhydrazones 7 and 8 and ferrocenylquinoxaline amide 57 showed interesting antimycobacterial activities.