The Gallides SrRh2Ga2, SrIr2Ga2, and Sr3Ir4Ga4

The gallides SrRh₂Ga₂, SrIr₂Ga₂, and Sr₃Rh₄Ga₄ were obtained from the elements by induction melting and subsequent annealing. They were investigated by powder and single‐crystal X‐ray diffraction: CaRh₂B₂ type, Fddd, a = 573.2(1), b = 1051.3(1), c = 1343.7(2) pm, wR₂ = 0.0218, 398 F² values, 15 variables for SrRh₂Ga₂; a = 576.0(1), b = 1045.5(1), c = 1350.6(3) pm for SrIr₂Ga₂, and Na₃Pt₄Ge₄ type, I$\bar{4}$ 3m, a = 777.4(2) pm, wR₂ = 0.0234, 190 F² values, 11 variables for Sr₃Ir₄Ga₄. The gallides SrRh₂Ga₂ and Sr₃Ir₄Ga₄ exhibit complex, covalently bonded three‐dimensional [Rh₂Ga₂] and [Ir₄Ga₄] networks with short Rh–Ga (241–246 pm) and Ir–Ga (243–259 pm) distances. The strontium atoms fill large cages within these networks. They are coordinated by 8 Rh + 10 Ga in SrRh₂Ga₂ and by 4 Ir + 8 Ga in Sr₃Ir₄Ga₄. The structure of SrRh₂Ga₂ is discussed along with the monoclinic distortion variants HoNi₂B₂ and BaPt₂Ga₂ on the basis of a group‐subgroup scheme.     

Asymmetric Synthesis of Fully Substituted Cyclopentane‐Oxindoles through an Organocatalytic Triple Michael Domino Reaction

An efficient, highly stereoselective asymmetric synthesis of fully functionalized cyclopentanes bearing an oxindole moiety and several other functional groups in one pot has been developed. Key step is an organocatalytic triple Michael domino reaction forming three C?C bonds and six stereocenters, including a quaternary one. Starting from equimolar amounts of simple substrates, a high molecular complexity can be reached after a Wittig olefination in one pot. The new protocol can easily be scaled up to gram amounts.     

NHC‐Catalyzed Asymmetric Synthesis of Functionalized Succinimides from Enals and α‐Ketoamides

The efficient asymmetric synthesis of highly substituted succinimides from α,β‐unsaturated aldehydes and α‐ketoamides via NHC‐catalyzed [3+2] cycloaddition has been developed. The new scalable protocol significantly expands the utility of NHC catalysis for the synthesis of heterocycles and provides easy access to assemble a wide range of succinimides from simple starting materials.     

Investigations of the Vicarious C‐Aminations of 5,7‐Dinitrobenzotriazole and 4,6‐Dinitrobenzotriazol‐3‐ium‐1‐oxide and Their Energetic Properties

This combined experimental and theoretical study details the vicarious nucleophilic substitution by amination of 5,7‐dinitrobenzotriazol ( 1 ) and 4,6‐dinitrobenzotriazole‐3‐ium‐1‐oxide ( 4 ) with trimethylhydrazinium iodide to afford the new corresponding one‐ and two‐time aminated compounds and investigations of its mechanism by EPR spectroscopy. The preferred position for the first amination is computed by spin density population and verified by X‐ray crystallography. The zwitterionic structure of 4 is investigated in solution by ¹H NMR spectroscopy and in solid state by X‐ray diffraction. Furthermore, the crystal structure of 1 is presented. The energetic behavior of the aminated products as well as the starting materials 1 and 4 was investigated, regarding sensitivities and performance.     

Chemical Evolution of a Bacterial Proteome

We have changed the amino acid set of the genetic code of Escherichia coli by evolving cultures capable of growing on the synthetic noncanonical amino acid L ‐β‐(thieno[3,2‐b]pyrrolyl)alanine ([3,2]Tpa) as a sole surrogate for the canonical amino acid L ‐tryptophan (Trp). A long‐term cultivation experiment in defined synthetic media resulted in the evolution of cells capable of surviving Trp→[3,2]Tpa substitutions in their proteomes in response to the 20 899 TGG codons of the E. coli W3110 genome. These evolved bacteria with new‐to‐nature amino acid composition showed robust growth in the complete absence of Trp. Our experimental results illustrate an approach for the evolution of synthetic cells with alternative biochemical building blocks.     

Contact between the β1 and β2 Segments of α‐Synuclein that Inhibits Amyloid Formation

Conversion of the intrinsically disordered protein α‐synuclein (α‐syn) into amyloid aggregates is a key process in Parkinson’s disease. The sequence region 35–59 contains β‐strand segments β1 and β2 of α‐syn amyloid fibril models and most disease‐related mutations. β1 and β2 frequently engage in transient interactions in monomeric α‐syn. The consequences of β1–β2 contacts are evaluated by disulfide engineering, biophysical techniques, and cell viability assays. The double‐cysteine mutant α‐synCC, with a disulfide linking β1 and β2, is aggregation‐incompetent and inhibits aggregation and toxicity of wild‐type α‐syn. We show that α‐syn delays the aggregation of amyloid‐β peptide and islet amyloid polypeptide involved in Alzheimer’s disease and type 2 diabetes, an effect enhanced in the α‐synCC mutant. Tertiary interactions in the β1–β2 region of α‐syn interfere with the nucleation of amyloid formation, suggesting promotion of such interactions as a potential therapeutic approach.     

A Gallium‐Substituted Distibene and an Antimony‐Analogue Bicyclo[1.1.0]butane: Synthesis and Solid‐State Structures

RGa {R=HC[C(Me)N(2,6‐iPr₂C₆H₃)]₂} reacts with Sb(NMe₂)₃ with insertion into the Sb? N bond and elimination of RGa(NMe₂)₂ ( 2 ), yielding the Ga‐substituted distibene R(Me₂N)GaSb?SbGa(NMe₂)R ( 1 ). Thermolysis of 1 proceeded with elimination of RGa and 2 and subsequent formation of the bicyclo[1.1.0]butane analogue [R(Me₂N)Ga]₂Sb₄ ( 3 ).     

Structure Elucidation and Activity of Kolossin A,the D‐/L‐Pentadecapeptide Product of a Giant Nonribosomal Peptide Synthetase

The largest continuous bacterial nonribosomal peptide synthetase discovered so far is described. It consists of 15 consecutive modules arising from an uninterrupted, fully functional gene in the entomopathogenic bacterium Photorhabdus luminescens. The identification of its cryptic biosynthesis product was achieved by using a combination of genome analysis, promoter exchange, isotopic labeling experiments, and total synthesis of a focused collection of peptide candidates. Although it belongs to the growing class of D ‐/ L ‐peptide natural products, the encoded metabolite kolossin A was found to be largely devoid of antibiotic activity and is likely involved in interspecies communication. A stereoisomer of this peculiar natural product displayed high activity against Trypanosoma brucei rhodesiense, a recalcitrant parasite that causes the deadly disease African sleeping sickness.     

Towards a world‐sheet description of doubled geometry in string theory

Starting from a sigma‐model for a doubled target‐space geometry, we show that the number of target‐space dimensions can be reduced by half through a gauging procedure. We apply this formalism to a class of backgrounds relevant for double field theory, and illustrate how choosing different gaugings leads to string‐theory configurations T‐dual to each other. We furthermore discuss that given a conformal doubled theory, the reduced theories are conformal as well. As an example we consider the three‐dimensional WZW model and show that the only possible reduced backgrounds are the cigar and trumpet CFTs in two dimensions, which are indeed T‐dual to each other.