Intracellular DNA Damage by Lysine-Acetylene Conjugates

Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and tunable family of DNA cleaving reagents. We also reported that, upon photoactivation, these molecules are capable of inducing cancer cells death. To prove that the cell death stems from DNA cleavage by the conjugates, we investigated intracellular DNA damage induced by these molecules in LNCap cancer cells using single cell gel electrophoresis (SCGE) assays. The observation of highly efficient DNA damage confirmed that lysine acetylene conjugate is capable of cleaving the densely compacted intracellular DNA. This result provides a key mechanistic link between efficient DNA cleavage and cytotoxicity towards cancer cells for this family of light-activated anticancer agents

Organocatalytic sulfoxidation

Treatment of a sulfide with a catalytic amount of a 1,3 diketone in the presence of silica sulfuric acid as a co-catalyst and hydrogen peroxide (50% aq) as the stoichiometric oxidant leads to the corresponding sulfoxide product. The reaction is effective for diaryl, aryl-alkyl and dialkyl sulfides and is tolerant of oxidisable and acid sensitive functional groups. Investigations have shown that the tris-peroxide 2, formed on reaction of pentane-2,4-dione with hydrogen peroxide under acidic reaction conditions, can oxidise two equivalents of sulfide using the exocyclic peroxide groups whereas the endocyclic peroxide remains intact. Calculations provide a mechanism consistent with experimental observations and suggest the reaction proceeds via an initial acid catalysed ring opening of a protonated tris-peroxide prior to oxygen transfer to a sulfur nucleophile

Chemistry: A Place to Publish Your Creative Multidisciplinary Research

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Stereoelectronic Interactions in Cyclohexane, 1,3-Dioxane, 1,3-Oxathiane, and 1,3-Dithiane: W-Effect, σ_C_-_X ↔ σ*_C_-_H Interactions, Anomeric EffectWhat Is Really Important?

Stereoelectronic effects proposed for C−H bonds in cyclohexane, 1,3-dioxane, 1,3-oxathiane, and 1,3-dithiane were studied computationally. The balance of three effects, namely, σC-X → σ*C-Heq, σC-Heq → σ*C-X, and np(X) → σ*C-Heq interactions, was necessary to explain the relative elongation of equatorial C(5)−H bonds. The role of homoanomeric np → σ*C(5)-Heq interaction is especially important in dioxane. In dithiane, distortion of the ring by long C−S bonds dramatically increases overlap of σC(5)-Heq and σ*C-S orbitals and energy of the corresponding hyperconjugative interaction. Anomeric np(X) → σ*C-Hax interactions with participation of axial C−H bonds dominate at C(2), C(4), and C(6). The balance of hyperconjugative interactions involving C−Hax and C−Heq bonds agrees well with the relative bond lengths for all C−Hax/C−Heq pairs in all studied compounds. At the same time, the order of one-bond spin−spin coupling constants does not correlate with the balance of stereoelectronic effects in dithiane and oxathiane displaying genuine reverse Perlin effect