Most associate liquid crystals with their everyday use in laptop computers, mobile phones, digital cameras, and other electronic devices. However, in contrast to their rodlike (calamitic) counterparts, first described in 1907 by Vorländer, disklike (discotic, columnar) liquid crystals, which were discovered in 1977 by Chandrasekhar et al., offer further applications as a result of their orientation in the columnar mesophase, making them ideal candidates for molecular wires in various optical and electronic devices such as photocopiers, laser printers, photovoltaic cells, light-emitting diodes, field-effect transistors, and holographic data storage. Beginning with an overview of the various mesophases and characterization methods, this Review will focus on the major classes of columnar mesogens rather than presenting a library of columnar liquid crystals. Emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties. Finally, some applications and perspectives in materials science and molecular electronics will be discussed.

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The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

Although catalytic reductions, cross‐couplings, metathesis, and oxidation of CC double bonds are well established, the corresponding catalytic hydroxylations of CH bonds in alkanes, arenes, or benzylic (allylic) positions, particularly with O2, the cheapest, “greenest”, and most abundant oxidant, are severely lacking. Certainly, some promising examples in homogenous and heterogenous catalysis exist, as well as enzymes that can perform catalytic aerobic oxidations on various substrates, but these have never achieved an industrial‐scale, owing to a low space‐time‐yield and poor stability. This review illustrates recent advances in aerobic oxidation catalysis by discussing selected examples, and aims to stimulate further exciting work in this area. Theoretical work on catalyst precursors, resting states, and elementary steps, as well as model reactions complemented by spectroscopic studies provide detailed insight into the molecular mechanisms of oxidation catalyses and pave the way for preparative applications. However, O2 also poses a safety hazard, especially when used for large scale reactions, therefore sophisticated methodologies have been developed to minimize these risks and to allow convenient transfer onto industrial scale.

A minimal CYP102A1 mutant library of only 24 variants plus wild type was constructed by combining five hydrophobic amino acids (alanine, valine, phenylalanine, leucine and isoleucine) in two positions. Both positions are located close to the centre of the haem group. The first, position 87, has been shown to mediate substrate specificity and regioselectivity in CYP102A1. The second hotspot, position 328, was predicted to interact with all substrates during oxidation and has previously been identified by systematic analysis of 31 crystal structures and 6300 sequences of cytochrome P450 monooxygenases. By systematically altering the size of the side chains, a broad range of binding site shapes was generated. All variants were functionally expressed in E. coli. The library was screened with four terpene substrates geranylacetone, nerylacetone, (4R)-limonene and (+)-valencene. Only three variants showed no activity towards all four terpenes, while eleven variants demonstrated either a strong shift or improved regio- or stereoselectivity during oxidation of at least one substrate as compared to CYP102A1 wild type.

Late-stage oxyfunctionalization of terpenoid scaffolds has been recognized as a powerful tool in the synthesis of complex molecules such as natural products to achieve their efficient diversification. Selective C−H oxidation of such hydrocarbon scaffolds remains challenging for chemical catalysts because of their insufficient regio-and stereoselectivity. To achieve this goal, cytochrome P450 monooxygenases are often used as biocatalysts. Here, we demonstrate the successful P450catalyzed chemo-, regio-, and stereoselective oxidation of the tobacco cembranoid β-cembrenediol. This 14-membered macrocycle possesses a broad range of biological activities including antitumor-promoting and neuroprotective effects and carries seven potential sites for allylic hydroxylation as well as three epoxidation sites. On the basis of first-sphere active site mutagenesis, we generated in a few rounds a P450 BM3 minimal library and screened for β-cembrenediol oxidation activity. Several P450 BM3 variants were evolved, enabling the regioselective hydroxylation of the neighboring positions C-9 (100% regioselectivity and a diastereomeric ratio of 89:11 in the case of the F87A/I263L mutant) and C-10 (97% regioselectivity and a diastereomeric ratio of 74:26 in the case of the L75A/V78A/F87G mutant) of β-cembrenediol.

This review presents the recent progress in the stereoselective formation of piperidines focussing on synthetic key steps. Both chiral pool-derived routes, auxiliary controlled methods and catalytic asymmetric reactions are described.

Die meisten Menschen verbinden mit dem Begriff Flüssigkristalle sofort die Displays von Laptop‐Computern, Mobiltelefonen, Digitalkameras und anderen elektronischen Geräten. Im Unterschied zu ihren stäbchenförmigen (calamitischen) Verwandten, die erstmals 1907 von Vorländer beschrieben wurden, bieten aber die 1977 von Chandrasekhar entdeckten scheibenförmigen (diskotischen) Flüssigkristalle andere vielversprechende Verwendungsmöglichkeiten. Ihre einzigartige Anordnung in columnaren Mesophasen macht sie zu idealen Kandidaten für molekulare Drähte in vielen optischen und elektronischen Geräten, beispielsweise in Photokopierern, Laserdruckern, Solarzellen, organischen Leuchtdioden und Feldeffekttransistoren oder zur holographischen Datenspeicherung. Einer Übersicht über die verschiedenen Mesophasentypen und Charakterisierungsmethoden columnarer Flüssigkristalle folgen ausgewählte Beispiele aus den Hauptklassen columnarer Mesogene unter besonderer Berücksichtigung effizienter Syntheseverfahren, mesomorpher Eigenschaften und der für Anwendungen relevanten physikalischen Eigenschaften der Flüssigkristalle. Abschließend werden Anwendungsbeispiele und Perspektiven für einen Einsatz in den Materialwissenschaften und der molekularen Elektronik vorgestellt.