W Tungsten

Sweet degradation: A designed fullerene–sugar hybrid selectively caused the degradation of HIV-1 protease, an important target of anti-HIV therapy. Degradation was achieved at irradiation with long-wavelength UV (365 nm) or visible light (diffuse sunlight) in the absence of any additives and under neutral conditions. Moreover, the hybrid inhibited HIV-1 replication in living cells infected with HIV-1.

The use of Pd catalysts that contained a carbene ligand, such as PEPPSI-SIPr, speeded up the Murahashi coupling of ArLi with ArBr, by enabling its integration with the Br/Li exchange of ArBr with BuLi in flow. Space integration realized the rapid cross-coupling of two different ArBr substrates. However, the cross-coupling reaction with vinyl halides could not be achieved under similar conditions. Pd(OAc)₂ was an effective catalyst, and the space integration of the Br/Li exchange of ArBr with BuLi and the Murahashi coupling with vinyl halides was successfully achieved.

Orinoco flow: Space integration of lithiation and Murahashi coupling reactions by using a flow microreactor system enabled the cross-coupling of aryl halides with aryl or vinyl halides.

The most-popular strategy to improve the cycling stability and rate performance of the sulfur electrode in lithium–sulfur (Li–S) batteries is to astrict the sulfur in a conducting medium by using complicated chemical/physical processing. Lithium sulfide (Li₂S) has been proposed as an alternative electrode material to sulfur. However, for its application, it must meet challenges such as high instability in air together with all of the drawbacks of a sulfur–containing electrode. Herein, we report the feasibility of using Li₂S, which was obtained by electrochemical conversion of commercial molybdenum disulfide (MoS₂) into Li₂S and metallic molybdenium (Mo) at low voltages, as a high-performance active material in Li–S batteries. Metallic Mo prevented the dissolution of lithium polysulfides into the electrolyte and enhanced the conductivity of the sulfide electrode. Therefore, the in situ electrochemically prepared Li₂S/Mo composite exhibited both high cycling stability and high sulfur utilization.

Batteries not included: The recharge products of deeply discharged MoS₂ were found to be metallic Mo and S. As Mo could not be oxidized below 3.0 V, Li₂S and S were thought to be the sole redox couple in the cell, S+2 Li↔Li₂S. The high cycling stability of the Li₂S/Mo nanocomposite demonstrated the feasibility of using Li₂S as an alternative to sulfur for lithium–sulfur batteries.

Proacetylenic: An aniline-based donor–acceptor-substituted butatriene exhibits not only cumulene-like dimerization to give a [4]radialene (λ_max=756 nm), but also acetylene-like (proacetylenic) reactivity towards tetracyanoethene, affording via [2+2] cycloaddition–cycloreversion a NIR-absorbing zwitterionic chromophore (λ_max=825 nm). The cationic charge on the imminium-type nitrogen in the zwitterion is evidenced by host–guest complexation with a tetraphosphonate cavitand.

The Pt^II-coordination complex [PtCl₂(DAB)] (DAB=2,3-diaminobutane) belongs to a class of cytotoxic cisplatin analogues that contain chiral diamine ligands. Enantiomeric pairs of these compounds have attracted particular interest because they have different effects on different DNA conformations, which, in turn, influences the binding of damaged-DNA-processing enzymes that control downstream effects of the adducts, and thus exhibit different biological activities of the enantiomers. Herein, we studied the translesion synthesis across the major 1,2-d(GG) intrastrand cross-link formed by the R,R and S,S enantiomers of [Pt(DAB)]²⁺ in the TGGT sequence by using the enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. We also employed differential scanning calorimetry (DSC) to measure the thermodynamic changes associated with replication-bypass past 1,2-d(GG) adducts of the [Pt(DAB)]²⁺ enantiomers. In the sequence TGGT, the 1,2-d(GG) intrastrand cross-links that were formed by the enantiomeric pairs of [Pt(DAB)]²⁺ inhibited DNA polymerization in a chirality-dependent manner. The thermodynamic data helped to understand the effect of the alterations in thermodynamic stability of DNA caused by the Pt-d(GG) adducts upon DNA polymerization across these lesions. Moreover, these data can possibly explain the influence of these alterations on the ability of many DNA polymerases to bypass adducts of antitumor platinum drugs. These results also highlighted the usefulness of DSC in evaluating the impact of DNA adducts of platinum-coordinated compounds on the processing of these lesions by damaged-DNA processing-enzymes.

A hard DNA’s night: The thermodynamics of chirality-dependent translesion synthesis by DNA polymerases across antitumor analogs of cisplatin are described.

The first semisynthesis of the tau protein is illustrated on the cover picture. This protein is known to aggregate upon phosphorylation, which makes it a key player in neurodegenerative diseases, such as Alzheimer's disease. In their Communication on page 2488 ff., C. P. R. Hackenberger, D. Schwarzer, et al. describe the chemical synthesis of the C-terminal phosphorylated part of tau, which they subsequently ligated to the N-terminal fragment of the protein produced in bacteria. Probably not as easy, but nevertheless similar to putting the final brick on a very popular childrens' game… (printed with kind permission from Lego^®).

Open chain Cbz-L-aa¹-L-Pro-Bt (Bt=benzotriazole) sequences were converted into either the corresponding trans- or cis-fused 2,5-diketopiperazines (DKPs) depending on the reaction conditions. Thermodynamic tandem cyclization/epimerization afforded selectively the corresponding trans-DKPs (69–75 %). Complementarily, tandem deprotection/cyclization led to the cis-DKPs (65–72 %). A representative set of proline-containing cis- and trans-DKPs has been prepared. A mechanistic investigation, based on chiral HPLC, kinetics, and computational studies enabled a rationalization of the results.

Stereoflexible route to DKPs: A convenient, versatile, and flexible benzotriazole-mediated methodology for the synthesis of proline-containing hetero-2,5-diketopiperazines (DKPs) is reported. Depending on the reaction conditions, either cis- or trans-configured DKPs were obtained starting from the same inexpensive l,l-dipeptidoyl benzotriazole key intermediate (see scheme). Kinetics, chiral HPLC, and computational studies forged a background for mechanistic rationalization.