Skeletal deformation vibrations and rotational isomerism of ethylenediamine and monoethanolamine

The infrared and Raman spectra of ethylenediamine hydrochloride, sulfate crystals, their N-deuterated compounds and ethylenediamine in the liquid and gaseous states and in cyclohexane solution were studied.The skeletal deformation vibration frequencies were found to be conformation sensitive and showed that the ethylenediamine molecule takes the trans and gauche forms in the liquid state and the gauche form in the gaseous state and in cyclohexane solution.The infrared and Raman spectra of monoethanolamine were studied in the liquid state. The spectra in the region for which the skeletal deformation vibration bands appear showed that the monoethanolamine molecule takes the trans and gauche form in the liquid state.     

Design of a robust Ru(salen) complex: aziridination with improved turnover number using N-arylsulfonyl azides as precursors

A new robust fluorinated (OC)Ru(salen) complex was designed on the basis of an X-ray structure of its parent complex to show improved turnover numbers (up to 878) and enantioselectivities (up to 99%) in aziridination reactions using p-toluenesulfonyl (Ts) or p-nitrobenzenesulfonyl (Ns) azide as the nitrene precursor; the latter is synthetically advantageous since the Ns group is N-protecting and can be removed under mild conditions.     

Short total synthesis of (+)-madindolines A and B

[reaction: see text] A short and efficient total synthesis of (+)-madindolines A (1) and B (2), potent and selective inhibitors of interleukin 6, has been achieved. The synthesis features a key chelation-controlled 1,4-diastereoselective acylation to generate the quaternary carbon and an intramolecular acylation of allylsilane to build up the cyclopentene unit.     

Structure-activity relationships of new N-acylanthranilic acid derivatives as plasminogen activator inhibitor-1 inhibitors

Novel anthranilic acid derivatives having substituted N-acyl side chains were designed and synthesized for evaluation as plasminogen activator inhibitor-1 (PAI-1) inhibitors. Compounds with a 4-diphenylmethyl-1-piperazinyl moiety on the acyl side chains in general exhibited potent in vitro PAI-1 inhibitory activity and good pharmacokinetic profiles after oral administration in rats. Compound 16f (TM5275) was identified as a promising candidate for further pharmacological evaluation.     

Extrathermodynamic Study of Retention Equilibrium in RP-LC Using a C18-Silica Monolithic Stationary Phase

This study is concerned with the explanation of some thermodynamic properties of the retention equilibrium on a C₁₈-silica monolithic column. Pulse response experiments were carried out in a reversed-phase liquid chromatography system using a methanol/water mixture (70/30, v/v) and n-alkylbenzene homologs as the mobile phase and sample compounds, respectively, in the temperature range between 278 and 318 K. The retention equilibrium constant (K _a) was calculated from the first absolute moment of elution peaks. The dependence of K _a on the column temperature was analyzed using the modified van??t Hoff plot proposed by Krug et al. to derive the changes of the Gibbs free energy, the enthalpy and the entropy concerning the retention behavior. First, the presence of a real enthalpy?Centropy compensation (EEC) for the retention equilibrium was demonstrated. Then, a thermodynamic model based on the real EEC was developed to explain the temperature dependence of the linear free energy relationship (LFER) of the retention equilibrium. The model indicates how the slope and intercept of the LFER are correlated with the compensation temperatures and several molecular thermodynamic parameters. The model was effective for explaining the thermodynamic properties of the retention equilibrium of the C₁₈-silica monolithic stationary phase.     

New high magnetic field phase of the frustrated <Emphasis Type="Italic">S</Emphasis> = 1/2 chain compound LiCuVO<Subscript>4</Subscript>

Magnetization of the frustrated S = 1/2 chain compound LiCuVO₄, focusing on high magnetic field phases, is reported. Besides a spin-flop transition and the transition from a planar spiral to a spin modulated structure observed recently, an additional transition was observed just below the saturation field. This newly observed magnetic phase is considered as a spin nematic phase, which was predicted theoretically but was not observed experimentally. The critical fields of this phase and its dM/dH curve are in good agreement with calculations performed in a microscopic model (M.E. Zhitomirsky and H. Tsunetsugu, Europhys. Lett. 92, 37001 (2010)).     

Crystals in Minutes: Instant On‐Site Microcrystallisation of Various Flavours of the CYP102A1 (P450BM3) Haem Domain

Despite CYP102A1 (P450BM3) representing one of the most extensively researched metalloenzymes, crystallisation of its haem domain upon modification can be a challenge. Crystal structures are indispensable for the efficient structure‐based design of P450BM3 as a biocatalyst. The abietane diterpenoid derivative N‐abietoyl‐l ‐tryptophan (AbiATrp) is an outstanding crystallisation accelerator for the wild‐type P450BM3 haem domain, with visible crystals forming within 2 hours and diffracting to a near‐atomic resolution of 1.22 Å. Using these crystals as seeds in a cross‐microseeding approach, an assortment of P450BM3 haem domain crystal structures, containing previously uncrystallisable decoy molecules and diverse artificial metalloporphyrins binding various ligand molecules, as well as heavily tagged haem‐domain variants, could be determined. Some of the structures reported herein could be used as models of different stages of the P450BM3 catalytic cycle.     

Stereospecific Cyclic Poly(methyl methacrylate) and Its Topology‐Guided Hierarchically Controlled Supramolecular Assemblies

In this study, the stereocomplexation between a novel stereospecific cyclic vinyl polymer, that is, cyclic syndiotactic poly(methyl methacrylate) (st‐PMMA), with the complementary linear isotactic (it‐) PMMA was investigated. Surprising new insight into the effects of the topology (i.e., end groups), size, and tacticity of the assembling components on stereocomplex formation was obtained. Characterization of the stereocomplexes revealed that the self‐assembly of cyclic st‐PMMAs and linear it‐PMMAs resulted in the formation of an unprecedented “polypseudorotaxane‐type” supramolecular assembly. This stereocomplex exhibited remarkably different physical properties as compared to the conventional PMMA triple‐helix stereocomplex as a result of the restricted topology imposed by the cyclic st‐PMMA assembling component.