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Research is presented demonstrating the catalysis of three distinct oxidative reactions during the biosynthesis of clavulanic acid by an Fe(II)/alpha-ketoglutarate-dependent oxygenase.

Abstract: Bergman Cyclization mediated cascade radical process is employed for the synthesis of [5]helicenes as well as diastereoselective mixtures of chiral amino acid appended [4]helicenes. Maximum selectivity (2.5:1) was found in case of l-leucine attached cyclic enediyne. Mechanistic considerations for this tandem radical reaction revealed that the major pathway probably involved quenching of the biradical, formed after aryl radical addition to pendant aromatic ring, by the solvent followed by aromatization. Intramolecular H-abstraction by the sp2-hybridized radical in the central ring or a 1,5-H shift followed by self-quenching could be the other possible ways to lead to the helicenes. [Copyright &y& Elsevier]

Development of new strategies for C-C bond formation remains in the forefront of organic synthesis. The base-mediated rearrangement of bis-propargyl sulfones via bis-allenes generated in situ, now known as the Garratt-Braverman cyclization (GBC), leads to the formation of two new C-C bonds. The reaction has recently drawn attention from organic chemists due to the wide scope as well as interesting mechanism. This report aims to give an account of the developments in this area with particular emphasis on synthetic applications. [ABSTRACT FROM AUTHOR]

Abstract: The reactivity of a series of bispropargyl sulfones with an ortho alkenyl moiety was studied. Under basic condition, these molecules isomerized to the bis-diene-allene system capable of undergoing 6π-electro-(EC) as well as Garratt–Braverman (GB) cyclization. The reaction generally favours the GB process but the balance can be tilted towards the 6π-EC pathway by suitable perturbation of structure and temperature. The findings are useful as the systems undergoing GB pathway can show DNA-damage activities. [Copyright &y& Elsevier]

Various indolyl carbazoles have been prepared in good yields utilizing Garratt-Braverman cyclization of bisindolyl propargyl sulfones, ethers, and amines as the key step. [ABSTRACT FROM AUTHOR]

Hydrogels are extensively studied as carrier matrices for the controlled release of bioactive molecules. The aim of this study was to design gelatin-based hydrogels crosslinked with genipin and study the impact of crosslinking temperature (5, 15 or 25°C) on gel strength, microstructure, cytocompatibility, swelling and drug release. Gels crosslinked at 25°C exhibited the highest Flory-Rehner crosslink density, lowest swelling ratio and the slowest release of indomethacin (Idn, model anti-inflammatory drug). Diffusional exponents ( n) indicated non-Fickian swelling kinetics while drug transport was anomalous. Hydrogel biocompatibility, in vitro cell viability, cell cycle experiments with AH-927 and HaCaT cell lines indicated normal cell proliferation without any effect on cell cycle. Overall, these results substantiated the use of genipin-crosslinked hydrogels as a viable carrier matrix for drug release applications. [ABSTRACT FROM AUTHOR]

Abstract: The reported ribonuclease A inhibitory activity of the green tea extracts prompted us to synthesize novel catechin/epicatechin based conjugates with resorcinol and phloroglucinol with the aim to increase the number of phenolic OH groups. These are found to be more effective inhibitors of ribonuclease A as compared to catechin and epicatechin thus indicating the importance of number of phenolic OH groups for the inhibition of ribonucleolytic activity. Fluorescence studies have been carried out to evaluate the binding parameters. The protein–ligand docking studies are also performed to gain insight into the protein–polyphenols interactions. The epicatechin based polyphenols 1 and 2 also showed inhibition of angiogenin-induced angiogenesis, as determined by chorioallantoic membrane (CAM) assay. [ABSTRACT FROM AUTHOR]

Abstract: C 2-Symmetric azobenzene-amino acid/peptide hybrids containing stable E-azo moiety have been synthesized. Upon irradiation with long wavelength UV, these compounds isomerized to the Z-form, whose thermal reisomerization to the E isomer slowed down considerably. These compounds exhibited in vitro moderate to strong inhibition of mammalian cellular protease Subtilisin Kexin Isozyme-1, also called Site 1 Protease, which plays vital roles in cholesterol synthesis, lipid metabolism, bone formation, and viral infections. [Copyright &y& Elsevier]

A competitive scenario between Myers-Saito (MS) and Garratt-Braverman (GB) cyclization has been created in a molecule. High-level computations indicate a preference for GB over MS cyclization. The activation energies for the rate-determining steps of the GB and MS cyclizations were found to be the same (24.4 kcal/mol) at the B3LYP/6-31G* level of theory; thus, from the kinetic point of view, both reactions are feasible. However, the main biradical intermediate GB2 of the GB reaction is 6.2 kcal/mol lower in energy than the biradical MS2, which is the main intermediate of MS reaction, so GB cyclization is thermodynamically favored over MS cyclization. To verify the prediction by computational techniques, bisenediynyl sulfones 1-4 and bisenediynyl sulfoxide 17 were synthesized. Under basic conditions, these molecules isomerized to a system possessing both the ene-yne-allene and the bisallenic sulfone. The isolation of only one product, identified as the corresponding naphthalene- or benzene-fused sulfone 8-11, indicated the occurrence of GB cyclization as the sole reaction pathway. No product corresponding to the MS cyclization pathway could be isolated. Though the theoretical prediction showed a preference for the GB pathway over the MS pathway, the exclusive preference for GB over MS cyclization is very striking. Further analysis showed that the intramolecular self-quenching nature of the GB pathway may play an important role in the complete preference for this reaction. Apart from the mechanistic studies, these sulfones showed DNA cleavage activity that had an inverse relation with the reactivity order. Our findings are important for the design of artificial DNA-cleaving agents. [ABSTRACT FROM AUTHOR]