G-quadruplex as a new class of structural entities for directing the formation of circular oligodeoxyribonucleotides

It has been demonstrated for the first time that G-quadruplex is capable of acting as a template for directing the sequence-specific formation of certain circular oligodeoxyribonucleotides with high efficiency.     

Solid-supported synthesis,deprotection and enzymatic purification of oligodeoxyribonucleotides

A simple solid-phase scheme for deprotection and enzymatic purification of oligodeoxyribonucleotides synthesized by a phosphoramidite method using hydrazine-sensitive protection is presented.     

First application of hexaaquaaluminium(III) tetrafluoroborate as a mild, recyclable, non-hygroscopic acid catalyst in organic synthesis: a simple and efficient protocol for the multigram scale synthesis of 3,4-dihydropyrimidinones by Biginelli reaction

For the first time hexaaquaaluminium(III) tetrafluoroborate has been used as a mild acid catalyst in organic synthesis. A simple method of its preparation based on the reaction of aluminium triisopropoxide and tetrafluoroboric acid in isopropanol afforded catalyst of high purity and activity. The three-component Biginelli condensation of acetoacetate esters, urea and aldehydes catalyzed by 10 mol % of [Al(H₂O)₆](BF₄)₃ in refluxing acetonitrile afforded 3,4-dihydropyrimidonones in good to high yields on multigram scales. The tolerance to acid sensitive reactants such as thienyl and furyl carbaldehydes, applicability to sterically hindered β-ketoesters and simple recyclability without losing catalytic activity make this catalyst as good replacement to literature methods. The mechanism of the reaction includes formation of the so called ‘ureido-crotonate’ rather than corresponding acylimino intermediate as found with Brønsted type catalysts.     

A new method for the synthesis of oligodeoxyribonucleotides containing 4-N-alkoxycarbonyldeoxycytidine derivatives and their hybridization properties.

Oligodeoxyribonucleotides incorporating 4-N-alkoxycarbonyldeoxycytidine derivatives were synthesized on polystyrene-type ArgoPore resins having a new benzyloxy(diisopropyl)silyl linker, by use of ZnBr(2) as the detritylating agent. The first 3'-terminal thymidine could be attached to the resin by successive in situ reactions of 5'-O-DMTr-thymidine with diisopropylsilanediyl ditriflate and an ArgoPore resin containing hydroxyl groups. The use of this new silanediyl-type linker allowed release of the DNA chain from the resin by treatment with TBAF under neutral conditions. The T(m) experiments apparently showed that incorporation of 4-N-alkoxycarbonyldeoxycytidines into DNA strands resulted in higher hybridization affinity with the complementary DNA strands than that of 4-N-acyldeoxycytidines. In addition, comparable T(m) studies using oligodeoxyribonucleotides incorporating acyl (RC(O)-) groups and alkoxyacyl (RO(CH(2))(n)C(O)-) groups having the same chain length show that the latter tend to exhibit higher T(m) values than the former. It turned out that 4-N-alkoxycarbonyldeoxycytidines can form base pairs not only with deoxyguanosine but also with deoxyadenosine. Based on the ab initio calculations of the hydrogen bond energies of the possible base pairs formed between 4-N-methoxycarbonyl-1-methylcytosine and 9-methyladenine and the NMR analysis of the base-pairs of (15)N-labeled 4-N-alkoxycarbonyldeoxycytidines with deoxyadenosine derivatives, we conclude that the base pair involves two unique hydrogen bonds between the cytosyl 4-NH group and the adenyl N(1) atom and between the O atom of the ester group and the adenyl 6-NH group.     

Ketones as a new synthon for quinoxaline synthesis

o-Phenylenediamines react with an array of ketones in PEG-400 at 60 °C under an atmosphere of air in the presence of KOH to afford the corresponding quinoxalines in good yields.     

Cyclopropenyllithiums as a new source of 1,1-bismetalated cyclopropyl derivatives

The allylmetalation of functionalised cyclopropenyllithium derivatives leads to the unique formation of 1,1-bismetalated cyclopropyl species that react selectively with different electrophiles.     

A synthesis of 4-carboxy-3-methylceph-3-em 1,1-dioxide involving a new strategy for the ring enlargement of penicillanate 1,1-dioxides

The title compound has been prepared from sulbactam sodium salt by a six-step sequence.     

Polymer-supported tetrafluorophenol: a new activated resin for chemical library synthesis

A new tetrafluorophenol activated resin that facilitates the use of 19F NMR to quantitate loading is presented. This new resin provides a useful tool for acylation, and a novel activated polymeric sulfonate ester to generate sulfonamides. This activated resin reacts with a wide scope of N-nucleophiles including primary and secondary amines, and anilines. This new activated resin methodology provides a powerful tool for pure single-compound library synthesis.     

A convenient, general synthesis of 1,1-dimethylallyl esters as protecting groups for carboxylic acids

[reaction: see text] Carboxylic acids were converted in high yield to their 1,1-dimethylallyl (DMA) esters in two steps. Palladium-catalyzed deprotection of DMA esters was shown to be compatible with tert-butyl, benzyl, and Fmoc protecting groups, and Fmoc deprotection could be carried out selectively in the presence of DMA esters. DMA esters were also shown to be resistant to nucleophilic attack, suggesting that they will serve as alternatives to tert-butyl esters when acidic deprotection conditions need to be avoided.     

Silica-bonded S-sulfonic acid as a recyclable catalyst for chemoselective synthesis of 1,1-diacetates

A simple and efficient procedure for the preparation of silica-bonded S-sulfonic acid (SBSSA) by reaction of 3-mercaptopropylsilica (MPS) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a recyclable catalyst for the synthesis of 1,1-diacetates from aromatic aldehydes and acetic anhydride under mild and solvent-free conditions at room temperature.     

On the chemical synthesis of new topological structures

The construction of chemical species with topological properties is an area of increasing interest. Numerous such structures have been synthesized in recent years, particularly from DNA, which is a natural synthon for these molecules. Recently, higher-order topological structures have been introduced. These hyper-structures consist of combinations of simple structures, such as a Brunnian Link of Brunnian Links or a Hopf Ring of Hopf Rings, or combinations thereof. In this article, we discuss the possibilities of constructing these hyper-structures with real molecules, particularly emphasizing the tools that result from the double helical structure of DNA.     

Nitroalkanes as new, ideal precursors for the synthesis of benzene derivatives

Nitroalkanes have emerged, in the past few years, as powerful acyclic building blocks to synthesize polyfunctionalized benzene derivatives, avoiding any serious regiochemical ambiguities due to the activating/deactivating and orienting effects of the substituents. Many of these procedures are realized in a one-pot process or a few-step sequence. This feature article describes recent results, mainly from our group, in this field.     

The triazine ring as a scaffold for the synthesis of new organogelators

The synthesis of new organogelators based on a triazine nucleus is described together with the analysis of the properties of the main compound 15. This compound revealed an efficient organogelator in both polar and apolar solvents and represents a promising precursor of other functionalized organogelators.     

一个得到1,1'-联-2-萘胺的合成新方法

以2-萘胺为原料,在甲醇溶液中与1.5eq的CuCl2·2H2O反应,氧化偶合得到1,1'-联-2-萘胺(1)与CuCl2的络合物沉淀。沉淀依次经沸水和氨水处理,得到产率56%的1。