Synthesis,structure, antimycobacterial and anticancer evaluation of new pyrrolo-phenanthroline derivatives

A study concerning design, synthesis, structure and in vitro antimycobacterial and anticancer evaluation of new fused derivatives with pyrrolo[2,1-c][4,7]phenanthroline skeleton is described. The strategy adopted for synthesis involves a [3?+?2] dipolar cycloaddition of several in situ generated 4,7-phenanthrolin-4-ium ylides to different substituted alkynes and alkenes. Stereo- and regiochemistry of cycloaddition reactions were discussed. The structure of the new compounds was proven unambiguously, single-crystal X-ray diffraction studies including. The antimycobacterial and anticancer activity of a selection of new synthesized compounds was evaluated against Mycobacterium tuberculosis H37Rv under aerobic conditions and 60 human tumour cell line panel, respectively. Five of the tested compounds possess a moderate antimycobacterial activity, while two of the compounds have a significant antitumor activity against renal cancer and breast cancer.     

Origins of regioselectivity in 1,3-dipolar cycloadditions of nitrile oxides with alkynylboronates

Density functional theory (M06-2X) studies of the regioselectivity of 1,3-dipolar cycloaddition reactions of benzo and mesitonitrile oxides with alkynyl pinacol and MIDA boronates are reported. Calculated relative free energies of activation reproduce the experimentally observed product ratios. The electronic energies of activation are found to be mainly controlled by distortion energies required to achieve the transition states. Both electronic and steric effects influence regioselectivities.     

Preparation of α- and β-dienyl glycosides used as dienes in aqueous Diels-Alder reactions. Influence of the carbohydrate moiety on the thermodynamics of the reaction

A series of 1,3-butadienyl glycosides (mono- and di-saccharides) have been prepared and the kinetics of their Diels-Alder reaction with buten-2-one in water have been studied. The activation parameters for these aqueous cycloadditions provide clues for the hydration structure of such glyco-organic compounds.     

Synthesis of oligonucleotides carrying 5'-5' linkages using copper-catalyzed cycloaddition reactions

There is considerable interest in coupling oligonucleotides to molecules and surfaces. Although amino- and thiol-containing oligonucleotides are being successfully used for this purpose, cycloaddition reactions may offer greater advantages due to their higher chemoselectivity and speed. In this study, copper-catalyzed 1,3-dipolar cycloaddition reactions between oligonucleotides carrying azido and alkyne groups are examined. For this purpose, several protocols for the preparation of oligonucleotides carrying these two groups are described. The non-templated chemical ligation of two oligonucleotides via copper-catalyzed [3+2] cycloaddition is described. By solid-phase methodology, oligonucleotides carrying 5'-5' linkages can be obtained in good yields.     

Conformational evaluation of some 4-deoxyhex-4-enopyranose derivatives and their use in the preparation of a previously undescribed class of 3-thio-L-sorbopyranosides and their 6-C-methoxy analogues

A new series of thio-substituted sugars were synthesised relying on the totally regio- and stereoselective cycloaddition of 4-deoxyhex-4-enopyranose derivatives to 'in situ' generated oxothiones. Conformational studies of the above unsaturated sugars showed a marked prevalence of the all-axial conformer.     

Chemical detection of carbon-metal bonds: From distinct sigma-bonding of main-group metals to ambiguous pi-bonding with transition metals

The detection, site of binding and quantification of bonds between carbon and a main-group metal can be readily achieved by a combination of proto- and deuteriodemetallation of such stable organometallics, combined with NMR spectral and mass spectrometric analyses of the organic products. Only with chiral sp³-carbon-metal bonds, with geometrically isomeric sp²-carbon-metal bonds or with allylic carbon-metal bonds will further structural physical data be required to identify the actual 3D-structure of the carbon binding site.The thermal and photochemical lability of carbon bonds to transition metals imposes restrictions on the detection of C−M_t bonds by deuteriodemetallation. Often the homolytic rupture of such bonds competes greatly and will lead to geometric isomers. Results of such apparent protodemetallation should be cross-checked with other structural information.The detection of C=M_t and possibly C≡M_t bonds may prove to be generally achievable by cycloadditions of such metal carbenes or carbynes with nitriles or alkynes.The addition of low-valent transition metal salts to alkenes or alkynes leads to complexes viewable as pi-complexes or as epimetallated adducts. By examination of available structural parameters and the chemical reactions undergone by such adducts, the adducts between ethylene and Ti(OiPr)₂ and between diphenylacetylene and α,α-bipyridyl-nickel(0) can best be considered as titana(IV)cyclopropane and nickel(II)cyclopropene structures, respectively.     

Scaffold oriented synthesis. Part 3: design, synthesis and biological evaluation of novel 5-substituted indazoles as potent and selective kinase inhibitors employing [2+3] cycloadditions

We report the synthesis and biological evaluation of 5-substituted indazoles and amino indazoles as kinase inhibitors. The compounds were synthesized in a parallel synthesis fashion from readily available starting materials employing [2+3] cycloaddition reactions and were evaluated against a panel of kinase assays. Potent inhibitors were identified for numerous kinases such as Rock2, Gsk3β, Aurora2 and Jak2.     

Synthesis of oligonucleotide derivatives using ChemMatrix supports

The synthesis of oligonucleotides on poly(ethylene glycol)-based (ChemMatrix) supports was studied. Results show that oligonucleotides can be indeed prepared in good yields using slightly modified synthesis cycles and automated DNA synthesizers. The use of these supports for the synthesis of oligonucleotide-peptide conjugates and for the ligation of oligonucleotides using Cu(+)-catalyzed cycloadition reactions is reported. Moreover, these supports can be used for the preparation of oligonucleotides in anhydrous solvents, followed by hybridization of the complementary sequences in aqueous buffers.     

Synthesis and biological evaluation of 4beta-[(4-substituted)-1,2,3-triazol-1-yl]podophyllotoxins as potential anticancer agents

A series of novel 4beta-[(4-substituted)-1,2,3-triazol-1-yl]podophyllotoxin derivatives were synthesized by employing Cu(I)-catalyzed click chemistry and evaluated for their anticancer activity against a panel of seven human cancer cell lines (HT-29, HCT-15, 502713, HOP-62, A-549, MCF-7, and SF-295). The compounds 9b, 9c, 9e, 9f, and 9h showed significant cytotoxic activities especially against HT-29, HCT-15, 502713 cell lines.