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The optical and chiroptical properties of an aza-HBC-oct-[5]helicene have been studied and also modulated by means of protonation or oxidation. In both cases, the generated species shows a new absorption band in the NIR region that is not present in the neutral species. This result enables this N-doped nanographene to act both as optical and, remarkably, as chiroptical switch since both the CD and CPL can be modulated by external stimuli such as redox or pH changes.

Brefeldin A is an important natural product and biochemical tool with cell-modulating and other diverse biological activities. To explore its chemical space, a generally applicable strategy for total syntheses of naturally occurring (+)-brefeldin A (BFA), 2-epi-BFA, their diastereomers and analogs with varying macrocyclic ring size is reported. The five-membered ring fragment was constructed by a short three-step sequence consisting of tandem nucleophilic epoxide opening/Brook rearrangement/radical oxygenation and subsequent thermal radical cyclization based on the persistent radical effect. Further key steps are asymmetric aldehyde vinylation, which enables control of the absolute configuration at the allylic hydroxy group of BFA, cross-metatheses reactions for attachment of the northern and southern side chains to the cyclopentane unit and final Shiina macrolactonization. The cytotoxic activity of all compounds was determined, and several analogs proved to be similarly active as BFA, providing insight about regions of the skeleton that can be varied or have to be conserved with respect to their biological activities. Fluorescence microscopy revealed that BFA and some non-natural analogs disassemble the Golgi apparatus in cells with large variation of the disassembly and subsequent reassembly times.

A reductive radical coupling reaction between non-activated aliphatic alcohols and styrenes has been discovered through the use of low-valent Ti-mediated C−O bond homolysis. A general application of styrene derivatives in radical coupling reactions remains a challenge in organic synthesis. The preliminary investigation revealed that the resulting benzyl radical intermediate behaves differently depending on minor steric differences around the spin center, which results in a lack of generality. The addition of 1,3,5-trimethyl-2,5-cyclohexadiene uniformly hydrogenated the benzyl radicals irrespective of the steric environments of the attacking radicals. Under the optimal reaction conditions, all tertiary, secondary, and primary alcohols were applicable. In this study, alcohols were successfully used directly as radical sources and reacted with a large number of styrenes.

Reaction networks of dynamic combinatorial libraries (DCLs) of cryptates were examined to better understand self-sorting, dynamic competition, and co-evolution processes. These findings, reported by Jean-Marie Lehn and co-workers in their Research Article, indicate that an increase in complexity (multiplicity and connectivity) of a system may, under dynamic competition, result in “simplexity”—a simplification of the output of the system—expressed in the self-sorting of its constituents.

Radical shielding weakens the C−C electron-pair bond between appropriately substituted methyl radicals. In their Research Article, F. Matthias Bickelhaupt and co-workers introduce the novel concept of the “Lone-Pair Shielded Radical“ (LPSR), in which the radical-electron orbital is surrounded, or shielded, by a lone-pair-like orbital. The latter causes closed-shell (Pauli) repulsion upon C−C bond formation, and thus reduces the stability of the dimer. This is shown on the left side of the cover illustration Dr. Daniela Rodrigues Silva designed. On the right side, the electron-pair bond is unhindered.

The Cover Feature shows the utilization of porphyrins attached to Colour Catcher® in mediating the photooxidation of amines or aldehydes. This innovative approach harnesses the power of white light and molecular oxygen, enabling cost-effective, time-efficient, and energy-saving reactions. In addition, the chemical stability, recyclability, and biodegradability of the Colour Catcher®-based photoactive material align with the growing societal need for the eco-friendly production of fine chemicals. More information can be found in the Research Article by Emma Gallo and co-workers.

Adding a complementary achiral monomer to polymers embedding a mixture of enantiopure monomers (the “sergeants”) and achiral monomers (the “soldiers”) is expected to decrease the optical purity of the polymer main chain. This study reports the influence of such achiral benzene-1,3,5-tricarboxamide (BTA) additives on the properties of “sergeants-and-soldiers” mixtures composed of an achiral BTA ligand coordinated to copper and of an enantiopure BTA monomer. Whilst N,N’,N’’-tris(octyl)benzene-1,3,5-tricarboxamide (BTA C8) shows no significant improvement in term of enantioselectivity in the catalytic reaction of reference, achiral BTA monomers derived from α,α’-disubstituted amino esters all lead to an increase in the selectivity at low “sergeant” ratio. This different behaviour was probed by characterizing the coassemblies embedding BTA C8, i. e. the worst-performing achiral additive, and the BTA derived from the ester of 1-aminocyclohexane carboxylic acid (BTA Achc), the best-performing one. Both additives were found to efficiently intercalate with the ligand and the “sergeant” leading to the formation of single helices. However, only the terpolymer embedding BTA Achc appears to be homochiral, accounting for the good enantioselectivity even at very low “sergeant” ratio (0.25 %).

Human serum albumin (HSA) efficiently transports drugs in vivo: most are organic. Here, HSA binding affinity and site specificity are shown to depend on the identity of the d⁸ metal ion in Ni^II, Pd^II and Pt^II chelates of the bis(pyrrole-imine) ligand H₂PrPyrr. Fluorescence quenching data for native and probe-bound HSA showed sites close to Trp-214 (subdomain IIA) are targeted. The Stern-Volmer constants, K_SV, ranged from 10⁴ M⁻¹ to 10⁵ M⁻¹ while the affinity constants, K_a, ranged from ∼3.5×10³ M⁻¹ to ∼1×10⁶ M⁻¹ at 37 °C, following the order Pd(PrPyrr) > Pt(PrPyrr) > Ni(PrPyrr) > H₂PrPyrr. Ligand uptake is enthalpically driven, hinging mainly on London dispersion forces. Induced CD spectra for the protein-bound ligands could be simulated by hybrid QM:MM TD-DFT methods, proving that the metal chelates neither decompose nor demetallate after uptake by HSA. Transport and delivery of the metal chelates by HSA in vivo could therefore be feasible.

We have quantum chemically analyzed the origin of the captodative effect in the dimerization of para-substituted phenyl dicyanomethyl radicals RPh(CN)₂C⋅ in the gas phase and in solution. Captodative radicals are characterized by the presence of both, electron-donating and electron-withdrawing groups, and a weakening of the associated C−C bond in the dimer of these radicals. Our quantitative bonding analyses reveal that the captodative weakening of the C−C bond is the consequence of a special feature in the RPh(CN)₂C⋅ electronic structure which we designate “lone-pair shielded radical”. Solvation effects weaken the C−C bond as the radicals have a more prominent internal charge separation than the dimer and are, therefore, stabilized more than the intact dimer. Interestingly, we find that differences in solvent effects as a function of the para-substituent in the most prominent case arise from variations in the charge distribution in the dimer, not from that in the separate radicals which experience very similar solvation in those instances.

Understanding dynamic systems is a crucial step toward the design of complex matter. Here, we aim to study the behavior of Constitutional Dynamic Networks (CDNs) in conditions of dynamic competition, taking cryptands and metal cations as a test bed. The CDNs of cryptates were analyzed by NMR spectroscopy. The experimental results were complemented by extensive numerical simulations, based on a large amount of thermodynamic and kinetic data available in the literature for cryptates. Although the CDN′s output is a result of the interplay between the individual stability constants of the complexes in a mixture, the overall effect may be governed by only one – the most thermodynamically stable member of a network. Significantly, these findings indicate that an increase in complexity (multiplicity and connectivity) of a system may, in conditions of dynamic competition, result in “simplexity”, i. e. a simplification of the output of the system.