Helicenophyrins: Expanded Carbaporphyrins Incorporating Aza[5]helicene and Heptacyclic S‐Shaped Aza[5]helicene Motifs

Incorporation of phenanthrene into a hexaphyrin(1.1.1.1.1.0) frame resulted in intramolecular ring fusion, thus giving rise to chiral helicenophyrins. These molecules contain helicene and porphyrin features by incorporating either an aza[5]helicene or heptacyclic S‐shaped aza[5]helicene.     

Synthesis of (−)‐Hebelophyllene E: An Entry to Geminal Dimethyl‐Cyclobutanes by [2+2] Cycloaddition of Alkenes and Allenoates

The first synthesis of hebelophyllene E is presented, along with assignment of its previously unknown relative configuration through synthesis of epi‐ent‐hebelophyllene E. Development of a catalytic enantioselective [2+2] cycloaddition of alkenes and allenoates provides access to the required chiral geminal dimethylcyclobutanes. Key to its success is the identification of a novel oxazaborolidine catalyst which promotes the cycloaddition in high enantioselectivities with good functional‐group tolerance (9 examples, up to 97:3 e.r.). Thus, a late‐stage cycloaddition using a fully functionalized alkene, followed by a diastereoselective reduction allows a concise entry to this class of natural products.     

Unsaturated four-membered N-heterocycles: From synthesis to applications

The ubiquity of strained motifs in drug discovery has recently witnessed a large regain of interest, as such scaffold can be used to modulate the properties of drug candidates. Unsaturated N-containing four-membered heterocycles present unique opportunities to access functionalized azetidines, which play an essential role in pharmacological studies. Even though those unsaturated patterns have been much less reported than the corresponding saturated versions, the consequent impact that those structures could have on molecular design with implementation of strained modules deserves to be summarized. In this review, synthetic accesses to substituted azetes, 1-azetines and 2-azetines are depicted, as well as their involvement in further transformations.     

Prediction of cathodic E1/21 and E1/22 values for viologen-containing conjugated unimers and dimers from calculated pKb values of the aromatic substituents

A library of 18 conjugated, rod-like compounds with either one or two viologen residues were synthesized and characterized electrochemically. Containing up to 8 aromatic/heterocyclic rings in conjugation, the members of the library differ in the substitution pattern of electron-withdrawing or -donating groups on the aromatic substituents of the viologen units. The first and second half-wave potentials of each member were found to be linearly correlated with the calculated pK_b values of the aromatic end-groups. This relationship will enable the half-wave potentials of related, novel, substituted viologen species to be predicted using a simple, empirical formula.     

Aqueous two-phase systems: A viable platform in the manufacturing of biopharmaceuticals

The number of biotechnology-based pharmaceuticals in the late-stage pipeline has been increasing more than ever. As a result, there is an enhanced demand for more efficient and cost-effective processes. During the last years, the upstream technology for the production of biopharmaceuticals has been considerably improved. Continuous discoveries in molecular biology and genetics, combined with new advances in media and feed development, have significantly increased the production titres. In order to keep up this gain, it is now essential to design new, as well as to improve the existing downstream processes that remain an unresolved bottleneck. This review evaluates several alternatives to the currently established platforms for the downstream processing biopharmaceuticals, with main focus on aqueous two-phase extraction.     

Feedback control design for Rössler and Chen chaotic systems anti-synchronization

The proposed anti-synchronization conditions of coupled chaotic systems are based, in this Letter, on the use of aggregation techniques for the stability study of the error dynamics. The schemes are, successfully, applied to coupled Rössler and Chen chaotic systems making the instantaneous characteristic matrix under the arrow form. Numerical simulations are performed to illustrate the efficiency of the proposed approach.     

Effect of highly filled ferrites on non-isothermal crystallization behavior of polyamide 6 bonded ferrites

The aim of this study is to characterize the non-isothermal crystallization of polyamide 6 bonded highly filled ferrites which were prepared by the melt extrusion. Especially, the effect of ferrite concentration and its surface property on the non-isothermal crystallization were investigated by means of differential scanning calorimetry. The highly filled ferrite particles acting as obstacles could severely hinder the motion of surrounding chain segments, which were irrespective of surface nature. The ferrite could be modified by silane and obtain a visually enhanced interaction with polymer matrix which evoked the heterogeneous nucleation. Increasing this enhanced interfacial area between polymer-particle can promote the heterogeneous nucleation. However, a strong interaction can slow the motion of surrounding chain segments of particles, thereby producing a competitive effect on the crystallization rate and crystallinity. The plot of crystallization activation energy against concentration also can evaluate dispersion performance of hydrophilic fillers within hydrophobic polymer.