Simultaneous Arrangement of up to Three Different Molecules on the Pore Surface of a Metal–Macrocycle Framework: Cooperation and Competition

Porous crystals are excellent materials with potential spatial functions through molecular encapsulation within the pores. Co‐encapsulation of multiple different molecules further expands their usability and designability. Herein we report the simultaneous arrangement of up to three different guest molecules, TTF (tetrathiafulvalene), ferrocene, and fluorene, on the pore surfaces of a porous crystalline metal–macrocycle framework (MMF). The position and orientation of adsorbed molecules arranged in the pore were determined by single‐crystal X‐ray diffraction analysis. The anchoring effect of hydrogen bonds between the hydroxy groups of the guest molecules and inter‐guest cooperation and competition are significant factors in the adsorption behaviors of the guest molecules. This finding would serve as a design basis of multicomponent functionalized nanospaces for elaborate reactions that are realized in enzymes.     

Annulation Approach to Doubly Linked (A‐type) Oligocatechins: Syntheses of (+)‐Procyanidin A2 and (+)‐Cinnamtannin B1

The first stereoselective syntheses of doubly linked (A‐type) oligocatechins, (+)‐procyanidin A₂ and (+)‐cinnamtannin B₁, have been achieved. Ethylenedioxy‐bridged flavans served as excellent platforms, thus allowing annulation with nucleophilic catechin units in a stereoselective manner. An additional key was the new synthetic approach to selectively protected nucleophilic catechin, thus enabling regioselective construction of the key dioxabicyclo skeleton of the A‐type oligocatechins.     

Superbenzene–Porphyrin Conjugates

A free‐base porphyrin carrying two hexabenzocoronene (HBC) substituents in a trans arrangement and its zinc complex have been prepared. The compounds were characterized extensively and found to form tricationic dimers in the gas phase. X‐ray crystallography confirms for the zinc complex a profound π‐stacking of the HBC moieties. In contrast, the free‐base porphyrin incarcerates n‐heptane which essentially prevents π‐stacking. Upon excitation of the HBC substituents, efficient energy transfer to the central porphyrin is observed.     

Ab Initio MP2 and Density Functional Theory Computational Study of AcAlaNH2 Peptide Hydration: A Bottom‐Up Approach

AcAlaNH₂?n H₂O (n=1–13) complexes have been proposed as models to account for water solvent effects on the molecular properties of N‐acetyl‐L ‐alanine amide. Ab initio computations are planned to evaluate peptide–water interactions and to provide a means for approximating relative effects of the short‐range many‐body interactions arising in real solution without introducing any external parameters intended to quantify empirical or semiempirical potential‐energy functions. The present bottom‐up approach reveals the formation of compact ring clusters of water molecules strongly bonded to peptidic polar groups throughout hydrogen bonds. The explicit coordination of water molecules around the peptide renders the fully extended (FE) and polyproline II (PPII) conformers more stable with respect to the 3₁₀ helix or γ turn. The alternance of donor and acceptor groups on both sides of the FE and PPII conformers allows for synergy and extensive H‐bonding.     

Energetic N,N′‐Ethylene‐Bridged Bis(nitropyrazoles): Diversified Functionalities and Properties

A new class of N,N′‐ethylene‐bridged bis(nitropyrazoles) was synthesized and fully characterized. The highly efficient formation of the N,N′‐ethylene bridge was accomplished using dibromoethane and ammonium or potassium pyrazolate. Further functional‐group transformations of diaminobis(pyrazole) and dichlorobis(pyrazole) gave rise to diversified derivatives, including dinitramino‐, diazido‐ and hexanitrobis(pyrazole). Single‐crystal X‐ray diffractions were obtained for hexanitro and diazido derivatives to illustrate the structural characteristics. Heats of formation and detonation performance were calculated by using Gaussian 03 and EXPLO5 v6.01 programs, respectively. Because of the different functionalized groups, the impact and friction sensitivities of these new compounds range from insensitive to sensitive. Among them, the hexanitro derivative displays the most promising overall energetic properties (density (ρ)=1.84 g cm^?3; decomposition temperature (T_d)=250 °C; detonation pressure (P)=34.1 GPa; detonation velocity (v_D)=8759 m s^?1; impact sensitivity (IS)=25 J; friction sensitivity (FS)=160 N), which is competitive with those of 1,3,5‐trinitrotriazacyclohexane (ρ=1.80 g cm^?3; T_d=205 °C; P=35.0 GPa; v_D=8762 m s^?1; IS=7 J; FS=120 N).     

Vibrational Spectrum and Gas‐Phase Structure of Disulfur Dinitride (S2N2)

Gas‐phase FTIR spectra of the ν₆ (B‐type) and the ν₄ (C‐type) fundamental bands of S₂N₂ (D_2h) were recorded with a resolution of ≤0.004 cm^?1 and the vibrational spectrum of S₂N₂ (D_2h) in solid Ar has been revisited. All IR‐active fundamentals and four combination bands were assigned in excellent agreement with calculated values from anharmonic VPT2 and VCI theory based on (explicitly correlated) coupled‐cluster surfaces. Accurate experimental vibrational ground‐ and excited‐state rotational constants of ³²S₂¹⁴N₂ are obtained from a rovibrational analysis of the ν₆ and ν₄ fundamental bands, and precise zero‐point average r_z (R_z(SN)=1.647694(95) Å, α_z(NSN)=91.1125(33)°) and semi‐experimental equilibrium structures (R_e(SN)=1.64182(33) Å, α_e(NSN)=91.0716(93)°) of S₂N₂ have been established. These are compared to the solid‐state structure of S₂N₂ and structural properties of related sulfur nitrogen compounds and to results of ab initio structure calculations.     

Selectfluor and NFSI exo‐Glycal Fluorination Strategies Applied to the Enhancement of the Binding Affinity of Galactofuranosyltransferase GlfT2 Inhibitors

Two complementary methods for the synthesis of fluorinated exo‐glycals have been developed, for which previously no general reaction had been available. First, a Selectfluor‐mediated fluorination was optimized after detailed analysis of all the reaction parameters. A dramatic effect of molecular sieves on the course of the reaction was observed. The reaction was generalized with a set of biologically relevant furanosides and pyranosides. A second direct approach involving carbanionic chemistry and the use of N‐fluorobenzenesulfonimide (NFSI) was performed and this method gave better diastereoselectivities. Assignment of the Z/E configuration of all the fluorinated exo‐glycals was achieved based on the results of HOESY experiments. Furthermore, fluorinated exo‐glycal analogues of UDP‐galactofuranose were prepared and assayed against GlfT2, which is a key enzyme involved in the cell‐wall biosynthesis of major pathogens. The fluorinated exo‐glycals proved to be potent inhibitors as compared with a series of C‐glycosidic analogues of UDP‐Galf, thus demonstrating the double beneficial effect of the exocyclic enol ether functionality and the fluorine atom.     

Dendrimer‐Type Peptoid‐Decorated Hexaphenylxylenes and Tetraphenylmethanes: Synthesis and Structure in Solution and in the Gas Phase

Branched organic nanostructures are useful scaffolds that find multiple applications in a variety of fields. Here, we present a novel approach to dendrimer‐like structures. Our design contains a rigid hydrocarbon‐based core (hexaphenylxylylene/tetraethynylphenylmethane) combined with a library of N‐substituted oligoglycines (so‐called peptoids) providing a flexible shell. The use of click chemistry allows rapid assembly of the nanostructures. The possibility of tuning the size and the solubility of this new type of nanostructure will be advantageous for future applications such as heterogeneous catalysis.     

Stereochemistry and Conformation of Skyllamycin,a Non‐Ribosomally Synthesized Peptide from Streptomyces sp. Acta 2897

Skyllamycin is a non‐ribosomally synthesized cyclic depsipeptide from Streptomyces sp. Acta 2897 that inhibits PDGF‐signaling. The peptide scaffold contains an N‐terminal cinnamoyl moiety, a β‐methylation of aspartic acid, three β‐hydroxylated amino acids and one rarely occurring α‐hydroxy glycine. With the exception of α‐hydroxy glycine, the stereochemistry of the amino acids was assigned by comparison to synthetic reference amino acids applying chiral GC‐MS and Marfey‐HPLC analysis. The stereochemistry of α‐hydroxy glycine, which is unstable under basic and acidic conditions, was determined by conformational analysis, employing a combination of data from NOESY‐NMR spectroscopy, simulated annealing and free MD simulations. The simulation procedures were applied for both R‐ and S‐configured α‐hydroxy glycine of the skyllamycin structure and compared to the NOESY data. Both methods, simulated annealing and free MD simulations independently support S‐configured α‐hydroxy glycine thus enabling the assignment of all stereocenters in the structure of skyllamycin and devising the role of two‐component flavin dependent monooxygenase (Sky39) as S‐selective.     

The Most Stable Isomers of Giant Fullerenes C102 and C104 Captured as Chlorides,C102(603)Cl18/20 and C104(234)Cl16/18/20/22

The chlorination of HPLC fractions with pristine giant fullerenes, C₁₀₂ and C₁₀₄, followed by X‐ray crystallographic study of chlorides, C₁₀₂(603)Cl_18/20 and C₁₀₄(234)Cl_16–22, confirmed the presence of the most stable IPR (IPR=Isolated Pentagon Rule) isomers, C₁₀₂(603) and C₁₀₄(234), in the fullerene soot. The discussion concerns the chlorination patterns of polychlorides and relative stability of pristine isomers of C₁₀₂ and C₁₀₄ fullerenes.