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Leukotriene B4 (LTB4) is a potent, proinflammatory lipid mediator implicated in the pathologies of an array of inflammatory diseases and cancer. The biosynthesis of LTB4 is regulated by the leukotriene A4 hydrolase (LTA4H). Compounds capable of limiting the formation of LTB4, through selective inhibition of LTA4H, are expected to provide potent anti-inflammatory and anti-cancer agents. The aim of the current study is to obtain potential LTA4H inhibitors using computer-aided drug design. A hybrid 3D structure-based pharmacophore model was generated based on the crystal structure of LTA4H in complex with bestatin. The generated pharmacophore was used in a virtual screen of the Maybridge database. The retrieved hits were extensively filtered, then docked into the active site of the enzyme. Finally, they were consensually scored to yield five hits as potential LTA4H inhibitors. Consequently, the selected hits were purchased and their biological activity assessed in vitro against the epoxide hydrolase activity of LTA4H. The results were very promising, with the most active compound showing 73.6% inhibition of the basal epoxide hydrolase activity of LTA4H. The results from this exploratory study provide valuable information for the design and development of more potent and selective inhibitors.

The enzyme glyoxalase-I (Glo-I) is an essential therapeutic target in cancer treatment. Significant efforts have been made to discover competitive inhibitors of Glo-I as potential anticancer agents. Herein, we report the synthesis of a series of diazenylbenzenesulfonamide derivatives, their in vitro evaluation against Glo-I and the resulting structure-activity relationships. Among the compounds tested, compounds 9h and 9j exhibited the highest activity with IC50 1.28 µM and 1.13 µM, respectively. Docking studies to explore the binding mode of the compounds identified key moieties that may contribute to the observed activities. The active compounds will serve as suitable leads for further chemical optimization.

In a previous report, we described the discovery of (E)-5-((8-hydroxyquinolin-5-yl)diazenyl)-2-methylbenzenesulfonamide as a potent inhibitor of GLO-I enzyme with IC

It has been postulated that sugar radicals and related species are involved in oxidative events involving RNA. To determine the contribution, if any, of these species to the deleterious effects of the endogenous exposome, it is important to unambiguously identify their degradation products. C5'-Pivaloyl uridine was successfully synthesized and subsequently photolytically converted to a C5'-uridinyl radical. Generation of the radical under anaerobic conditions in the presence of glutathione led to the formation of the expected reduction product, uridine. However, regardless of the presence or absence of reductant, the base elimination product, uracil, was also observed. Mass balances and product distributions were dependent upon the pH of the photolysis mixture. At low pH, trapping with glutathione successfully competed with base loss. These results indicate that this precursor should function efficiently in an investigation of the fate of the C5'-uridinyl radical in RNA oligomers.

Oxidative events that take place during regular oxygen metabolism can lead to the formation of organic or inorganic radicals. The interaction of these radicals with macromolecules in the organism and with DNA in particular is suspected to lead to apoptosis, DNA lesions and cell damage. Independent generation of DNA lesions resulting from oxidative damage is used to promote the study of their effects on biological systems. An efficient synthesis of oligodeoxyribonucleotides (ODNs) containing the oxidative damage lesion 3'-oxothymidine has been accomplished via incorporation of C3'-hydroxymethyl thymidine as its corresponding 5'-phosphoramidite. Through oxidative cleavage using sodium periodate in aqueous solution, the lesion of interest is easily generated. Due to its inherent instability it cannot be directly isolated, but must be generated in situ. 3'-Oxothymidine is a demonstrated damage product formed upon generation of the C3'-thymidinyl radical in ODN.

Well-defined substrates for the study of oxidative processes are important for the elucidation of the role of DNA damage in the etiology of diseases such as cancer. We have synthesized 3′-modified oligodeoxyribonucleotides (ODNs) using 5′ → 3′ ‘reverse’ DNA synthesis for the study of 2-deoxyribose oxidative damage to DNA. The modified monomers designed for these studies all share a common feature, they lack the naturally occurring 3′-hydroxyl group found in 2-deoxyribonucleosides. Modified H-phosphonates containing 3′-phenyl selenides as well as saturated and unsaturated sugars were obtained and incorporated in ODNs. These ODNs were used to investigate the fate of C3′-dideoxyribonucleotide radicals in DNA.

DNA damage pathways induced by low-energy electrons (LEEs) are believed to involve the formation of 2-deoxyribose radicals. These radicals, formed at the C3' and C5' positions of nucleotides, are the result of cleavage of the C-O phosphodiester bond through transfer of LEEs to the phosphate group of DNA oligomers from the nucleobases. A considerable amount of information has been obtained to illuminate the identity of the unmodified oligonucleotide products formed through this process. There exists, however, a paucity of information as to the nature of the modified lesions formed from degradation of these sugar radicals. To determine the identity of the damage products formed via the 2',3'-dideoxy-C3'-thymidinyl radical (C3'(dephos) sugar radical), phenyl selenide and acyl modified sugar and nucleoside derivatives have been synthesized, and their suitability as photochemical precursors of the radical of interest has been evaluated. Upon photochemical activation of C3'-derivatized nucleosides in the presence of the hydrogen atom donor tributyltin hydride, 2',3'-dideoxythymidine is formed indicating the selective generation of the C3'(dephos) sugar radical. These precursors will make the identification and quantification of products of DNA damage derived from radicals generated by LEEs possible.

C-3′-Acyl-3′-xylothymidine-containing oligonucleotides have been designed and synthesized for their use as radical precursors in the study of oxidative DNA damage initiated by a C-3′-radical. These oligomers were efficiently obtained using automated DNA synthesis techniques based on H -phosphonate chemistry. CD spectra and melting curves of the synthesized oligonucleotides were compared to those of their unmodified and xylomodified counterparts. The conformational analysis and hybridization studies indicate that the combination of the photolabile acyl group and the inversion of configuration at the sugar has no profound effect on the overall conformation of C-3′-acyl-2′-deoxy-3′-xylonucleotides as compared to their natural analogues. These systems should provide excellent tools for the elucidation of DNA damage processes.

The stepwise palladium-catalyzed coupling of dibromo-1,6-methano[10]annulene derivatives to a phenyl-acetylene substituted by an electron-withdrawing group followed by coupling with a phenylacetylene possessing an electron-donating group allows the preparation of donor/acceptor systems which contain three aromatic moieties linked by ethynediyl bridges. The same type of cross-coupling starting from 2-ethynyl-1,6-methano[10]annulene and bromo-substituted azobenzene derivatives provides easy access to a new class of azo dyes. The properties of these compounds are compared to those of analogous compounds containing only benzene rings.

The treatment of bromo-substituted 1,6-methano[10]annulenes with sodium thiolates in DMF provides easy access to alkylthio- and arylthio-substituted 1,6-methano[10]annulenes (Schemes 2-4). These compounds are then brominated with N-bromosuccinimide (NBS) to study their reactivity in electrophilic substitution reactions (Schemes 5 and 6). The resulting brominated thio-1,6-methano[10]annulenes are, in a subsequent reaction, subjected to Heck coupling with (4-nitrophenyl)acetylene (13) to produce the alkynylated derivatives 14 in reasonable yield (Scheme 7).

What's the damage? Trapping the C3'-thymidinyl radical in biologically significant architectures delivers both the repaired oligomer and 1-(2'-deoxy-β-D-threo-pentofuranosyl)thymidine-containing substrates. The stereoselectivity of the reduction was found to be dependent upon the DNA structure.

[reaction: see text] A C-3'-thymidinyl radical has been photochemically generated site-specifically in DNA oligonucleotides. A nucleoside H-phosphonate bearing a C-3' acetyl group was incorporated into DNA oligomers using a hand-coupling technique. When nucleotides containing the modified monomer were photolyzed (or =320 nm) in the presence of a hydrogen atom donor, reduction products were detected by RP-HPLC and MALDI-ToF MS analysis.

C-3'-nucleoside radicals can be generated via Norrish type I photocleavage of C-3'-acyl nucleoside derivatives. In monomer experiments employing C-3'-acylthymidine derivatives 2 and 3, a 1:1 mixture of isomers of the H-abstraction products was obtained when the photolysis was carried out in the presence of a hydrogen donor. Derivatives 2 were synthesized by an approach which involves the formation of a silyl-protected cyanohydrin, which is subsequently alkylated with organolithium reagents, followed by hydrolysis. Derivatives 3 could be obtained via a multistep synthesis starting from diol 7. Several different methods were attempted to oxidize the unprotected diol to the alpha-hydroxy aldehyde. Finally, a route was chosen which involves a protection-deprotection sequence followed by oxidation of the free primary alcohol. The resulting modified nucleosides should facilitate the study of C-3'-DNA radicals.