Stabilization of DNA triplexes by dangling aromatic residues

Novel nucleoside analogues containing 2^′-deoxyinosine and aromatic rings, which are connected by short linker groups, were synthesized and incorporated into oligodeoxyribonucleotides (ODNs). ODNs containing the nucleoside analogues formed stable duplexes and triplexes with target nucleic acids. The stacking interaction between base residues in the nucleoside analogues appears to be a major cause of stabilization.     

DFT study of “all-metal” aromatic compounds

An overview of recent quantum chemical studies on all-metal aromatic compounds is presented. Novel classes of inorganic molecules containing bonds that are characterized by a common ring-shaped electron density are reviewed. The mechanistic insight gained for the aromatic character of all-metal aromatic molecules is discussed and the predictive nature of the electronic structure calculation methods particularly those based on density functional theory (DFT) is highlighted. The indicators of aromaticity (aromaticity criteria) - structural, magnetic, energetic and reactivity-based measures - many of which are accessible through quantum chemical calculations are also outlined herein.     

Conjugate addition of aromatic amines to ethenetricarboxylates

The conjugate addition of amines is considered to be a useful reaction in synthetic organic chemistry. The reaction of reactive electrophilic olefins, ethenetricarboxylates, and aromatic amines with and without catalytic Lewis acids such as ZnCl₂ and ZnBr₂ at room temperature gave amine adducts in high yields. The products were converted to α-amino acid, dl-aspartic acid derivatives. Using Lewis acids such as Sc(OTf)₃ and Zn(OTf)₂ at higher temperature (40-80 °C), the reaction of ethenetricarboxylates and N-methylaniline gave an aromatic substitution product. A catalytic enantioselective conjugate addition using a chiral Lewis acid was also investigated. For example, the reaction of 1,1-diethyl 2-tert-butyl ethenetricarboxylate with N-methylaniline in the presence of chiral bisoxazoline-Cu(II) complex in THF at −20 °C for 17 h gave an amine adduct in 91% yield and 78% ee. On the other hand, the reaction with aniline and primary aniline derivatives gave adducts with almost no ee%.     

Oligodeoxyribonucleotide Activation with 2,4-Phenylenediisothiocyanate and Their Covalent Grafting onto Amine-Functionalized Latex Microspheres

The activation of various synthetic oligodeoxyribonucleotides (ODNs), bearing a hexamethylamine arm at their 5′-end, with the 2,4-phenylenediisothiocyanate (PDC) was studied. The activation reaction had to be performed within 40 min, because of competitive hydrolysis of the isothiocyanate functions. ODN modifications were then characterized by different analytical methods i.e. gel capillary electrophoresis, Matrix-Assisted Laser Desorption-Ionization-Time of Flight (MALDI-TOF) mass spectrometry. Moreover, activation of the amine groups of the nucleic bases was evidenced through the chemical analysis of the enzymatic-digested conjugate (PDC-ODN) by reverse phase HPLC. Preliminary results on the covalent grafting of activated ODN molecules onto the aminated latex particles showed that the amount of grafted ODNs was directly related to the number of potential grafting sites on the nucleic acid probe (primary amine group of hexamethyl arm and amine functions of the nucleic bases).     

铜催化芳香醛和酮的氢硼化转化合成苄基硼酸酯类化合物（英文）

有机硼化合物广泛应用于合成化学、药物化学以及材料化学等领域,开发新颖实用的方法合成有机硼化合物是重要的研究领域.在各种有机硼化合物中,苄基硼酸酯有着一些特有的性质,例如活性相对较高,可以有效地当作苄基化试剂使用.目前已有多种合成苄基硼酸酯的方法,主要集中在苄基格氏试剂或者锂试剂的硼化反应,但是该方法底物兼容性较差,而且苄基格氏试剂或者锂试剂的制备比较困难.随着催化反应的发展,过渡金属(如Pd,Cu,Ni,Fe)催化苄基卤代物的硼化反应及芳基卤代物和1,1-二硼类化合物的偶联反应能够有效地合成这类化合物.一级苄醇在钯或铜的催化作用下也可以转化为苄基硼酸酯.苄基C–H键的催化硼化是潜在的构建苄基硼酸酯的高原子经济性的方法,但目前其选择性和反应活性仍不高.在无金属催化的条件下,对甲苯磺酰腙类化合物与HBpin或B_(2pin_2)发生1,2-金属迁移是合成苄基硼酸酯的有效方法.到目前为止,虽然有很多种合成苄基硼酸酯的方法,但仍无法满足其合成需求,因此开发新型的方法合成苄基硼酸酯具有重要的意义.本文开发了一种新型的铜催化芳香醛/酮类化合物的脱氧氢硼化转化体系.使用廉价易得的铜作为催化剂,叔丁醇钠或者叔丁醇钾作为碱,醇质子作为氢源,在100℃的条件下,芳香醛和芳香酮可直接转化成一级和二级苄基硼酸酯类化合物,该反应操作简单,反应体系可以兼容多种官能团,分离产率在21%–77%之间.反应机理方面,该转化有两种可能的过程,(1)反应体系中首先生成1,1-偕二硼化合物,该化合物在碱和EtOH的作用下发生脱硼质子解,最终转化成苄基单硼化合物;(2)醇质子转化成负氢物种,并与体系中的冄-OBpin硼酸酯生成四配位硼,发生1,2-迁移后得到目标产物.为了验证上述两种反应途径的可行性,我们进行了一系列的控制试验.首先合成了苯乙酮的1,1-二硼化合物,在催化量碱与当量醇的作用下,以99%的收率得到了脱硼质子解的产物,说明1,1-二硼化合物可以在反应体系中转化成苄基单硼化合物.以苯甲醛作为原料合成了冄-OBpin硼酸酯,首先将其投入到甲醇、叔丁醇钠和B_(2pin_2)的体系中,最终得到了47%的苄基单硼;同时将冄-OBpin硼酸酯投入到HBpin与叔丁醇钠的体系中,得到了57%的苄基单硼化合物,说明第二种反应过程通过1,2-迁移得到目标产物也是可行的.在当前的实验条件下,两种反应路径都是可能的.     

α-Oxoketene dithioacetal mediated aromatic annulation: highly efficient and concise synthetic routes to potentially carcinogenic polycyclic aromatic hydrocarbons

Highly efficient regiospecific routes to potentially carcinogenic polycyclic aromatic hydrocarbons such as substituted benzo[c]phenanthrenes, benzo[c]fluorenes, 16,17-dihydro-11-methyl-15[H]cyclopenta[a]phenanthrene, 5-methyl-7,8,9,10-tetrahydrochrysene and 1,4-dimethylphenanthrene have been developed. The overall strategy involves our aromatic annulation protocol through base induced conjugate addition-elimination on the cyclic and acyclic α-oxoketene dithioacetals with the appropriate arylacetonitriles followed by acid induced cyclodehydration of the resulting conjugate adducts. Subsequent reductive dethiomethylation (Raney Ni) and dehydrogenation (DDQ) of the cyclized products affords the methyl substituted PAHs in high yields.     

Substituent effects on aromatic stacking interactions

Synthetic supramolecular zipper complexes have been used to quantify substituent effects on the free energies of aromatic stacking interactions. The conformational properties of the complexes have been characterised using NMR spectroscopy in CDCl(3), and by comparison with the solid state structures of model compounds. The structural similarity of the complexes makes it possible to apply the double mutant cycle method to evaluate the magnitudes of 24 different aromatic stacking interactions. The major trends in the interaction energy can be rationalised using a simple model based on electrostatic interactions between the pi-faces of the two aromatic rings. However, electrostatic interactions between the substituents of one ring and the pi-face of the other make an additional contribution, due to the slight offset in the stacking geometry. This property makes aromatic stacking interactions particularly sensitive to changes in orientation as well as the nature and location of substituents.     

One-pot conversion of aromatic bromides and aromatics into aromatic nitriles via aryllithiums and their DMF adduct

Various aromatic bromides and iodides were smoothly converted into the corresponding aromatic nitriles in good to moderate yields by the treatment with n-butyllithium and subsequently DMF, followed by treatment with molecular iodine in aq NH₃. The same treatment of typical aromatics and heteroaromatics with n-butyllithium and subsequently DMF, followed by treatment with molecular iodine in aq NH₃ also provided the corresponding aromatic nitriles in good yields. Moreover, the same treatment of aromatic bromides and aromatics with half amount of DIH (1,3-diiodo-5,5-dimethylhydantoin) instead of molecular iodine worked effectively to give the corresponding aromatic nitriles, respectively, in good yields. These reactions are novel and environmentally benign one-pot methods for the preparation of aromatic nitriles from aromatic bromides and aromatics, respectively, through the formation of aryllithiums and their DMF adducts.     

Hydrogel formation via hybridization of oligonucleotides derivatized in water-soluble vinyl polymers

Succinimido-copolymers, poly(N,N-dimethylacrylamide-co-N-acryloyloxysuccinimide)s, were coupled with 5′-terminal-amino-modified oligodeoxyribonucleotides (ODNs) to produce water-soluble copolymers partially derivatized with ODNs in their side chains. The mixing and thermal melting measurements of dilute mixed aqueous solutions of an ODN-derivatized copolymer and their complementary ODN and mixed solutions of complementary ODN-derivatized copolymers were monitored by ultraviolet spectroscopy. The results showed that hybrids were formed with their complementary ODNs at room temperature, but dissociated at high temperature. Based on the hybridization between complementary base pairs of nucleic acids and its thermal dissociation characteristics, two types of thermoresponsive hydrogels were prepared: (1) a hydrogel formed via hybridization between an oligodeoxythymidylate (oligoT)-derivatized copolymer and an oligodeoxyadenylate (oligoA), and (2) a hydrogel formed by hybridization between complementary oligoT- and oligoA-derivatized copolymers. Thus, selfassociation due to specific intermolecular hydrogen bonding between nucleic acid base pairs enabled the preparation of a novel thermoresponsive hydrogel.     

Non-flammable and reusable hydrogenation of aromatic ketones in ionic liquid

A novel method of hydrogenation of aromatic ketones in the ionic liquid [BHEA][HCO₂] was developed; this method is more enhanced in terms of flammability and reusability as compared to the conventional method (H₂ and Pd/C). The reductive selectivities of aromatic and aliphatic ketones in this method were observed.     

One-step three-component coupling of aromatic organozinc reagents, secondary amines, and aromatic aldehydes into functionalized diarylmethylamines

Numerous functionalized diarylmethylamines have been synthesized in high yield according to a one-step three-component coupling between an aromatic organozinc reagent, a secondary amine, and an aromatic aldehyde. Both organozinc species and aldehyde can bear a functional group and either aromatic or non-aromatic amines can be used in this versatile procedure.     

A novel aromatic alkylation of anilines with cyclic and acyclic ketones under hydrothermal conditions

A novel aromatic ring-alkylation was achieved by condensation between aniline·HCl salts and cyclic or acyclic ketones under hydrothermal conditions.     

Regiospecific oxidation of an alkyl group of aromatic amine to carbonyl group by DDQ in aq.medium

The regiospecific oxidation of alkyl group of both sterically hindered and unhindered aromatic amine to corresponding carbonyl compound was done in aq. medium by using DDQ. The optimized reaction protocol was found to be most simple, high yielding and novel method for oxidation of alkyl group of aromatic amine in to its carbonyl compound.     

Multiple-pyrene residues arrayed along DNA backbone exhibit significant excimer fluorescence

Oligodeoxyribonucleotides (ODNs) carrying multi-pyrene clusters were chemically prepared by introducing a novel nucleoside-pyrene conjugate into ODNs. The multi-pyrene residues arrayed on DNA strands induced significant excimer fluorescence and the intensity was exponentially increased as the number of pyrene residues in clusters increased. The excimer fluorescence of the arrays was stable and was not quenched by duplex formation.     

β-Cyclodextrin epichlorohydrin copolymer as a solid-phase extraction adsorbent for aromatic compounds in water samples

A novel solid-phase extraction (SPE) procedure for trace aromatic compounds in water samples has been developed using 12 aromatic compounds as model compounds and GC-MS and UV spectrophotometry for detection. The method is based on the fact that β-cyclodextrin (β-CD) epichlorohydrin (ECH) copolymer (β-CDEP) can extract non-ionized aromatic compounds quantitatively from aqueous samples. The polymer used is a colorless, transparent and insoluble solid with a maximum capacity of 0.82 μmol aromatic compounds per gram. It was synthesized by co-polymerization of β-CD and ECH and characterized by FT-IR and UV. β-CDEP does not contain double bonds, and therefore it does not have appreciable absorbance in the UV region. The optimum pH range for the extraction of aromatic compounds is 2.5-5.0. The method has high extraction efficiency with the recoveries between 90 and 101% for aromatic compounds at 0.02-1.67 ppm levels, and the analytes can be easily eluted by methanol washing after preconcentration.     

Substituent effects on edge-to-face aromatic interactions

Chemical double mutant cycles have been used to measure the magnitude of edge-to-face aromatic interactions in hydrogen-bonded zipper complexes as a function of substituents on both aromatic rings. The interaction energies vary depending on the combination of substituents from +1.0 kJ mol-1 (repulsive), to -4.9 kJ mol-1 (attractive). The results correlate with the Hammett substituent constants which indicates that electrostatic interactions are responsible for the observed differences in interaction energy. The experiments can be rationalised based on local electrostatic interactions between the protons on the edge ring and the pi-electron density on the face ring as well as global electrostatic interactions between the overall dipoles on the two aromatic groups.     

Highly specific N-monomethylation of primary aromatic amines

A synthetic methodology for the specific conversion of primary aromatic amines into their N-monomethyl derivatives under very mild conditions is presented. Anilines are treated with 4-nitrobenzenesulfonyl (nosyl) chloride to generate the corresponding sulfonamides 2 in high yields. The subsequent N-methylation reaction of the sulfonamides 2 with a solution of diazomethane is rapid and quantitative. Removal of the nosyl protecting group is readily carried out using the reagent system mercaptoacetic acid/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) affording the N-monomethylated aromatic amines 4. The procedure is convenient, efficient, and gives rise to the N-monomethyl-anilines exclusively.     

Use of functionalized aromatic organozinc reagents in the three-component Mannich-type synthesis of diarylmethylamines

Efficient syntheses of functionalized diarylmethylamines have been realized according to a one-step three-component coupling between an aromatic aldehyde, a secondary amine and an aromatic organozinc reagent. Phenyl rings can be substituted by functional groups and either aromatic or non-aromatic amines can be used in this process.     

Palladium-catalyzed ortho-selective C–H bond chlorination of aromatic ketones

A palladium-catalyzed ortho-selective C–H bond chlorination reaction for the preparation of 2-chloro aromatic ketones was described. Both electron-withdrawing and electron-donating groups on the aromatic rings are well tolerated under the optimized conditions. The 2-chloro aromatic ketones obtained by our method could be applied to synthesize the derivatives of 1H-indazole or benzo[d]isoxazole.     

Ionic liquids as designer solvents for nucleophilic aromatic substitutions

Ionic liquids were designed to optimize the nucleophilic aromatic substitution reaction of an activated aniline with an activated arylhalide. The design was achieved by selecting the anions on the basis of calculations of the gas-phase basicity of their conjugate acids.