Asymmetric catalysts for stereocontrolled olefin metathesis reactions

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Since the discovery of metathesis as an instrument to reorganize olefinic double bonds, substantial progress has been attained, establishing this method as a versatile and efficient tool for C–C-bond formation. In the last decade fundamental achievements were accomplished in the field of chiral Ru- and Mo-based olefin metathesis, providing an asymmetric access to structures, which are difficult to obtain by alternative routes. The reader is taken behind the scenes of catalyst development, important areas of application are described up to the current state of research; this tutorial review deals with the question, how metathesis is connected to enantioselective synthesis

New catalysts with unsymmetrical N-heterocyclic carbene ligands

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The importance of unsymmetrical N-heterocyclic carbenes (uNHCs) as ligands in metal-catalyzed reactions is undeniable. While uNHCs show similar properties as compared with symmetrical NHCs, dissymmetrization allows for further fine-tuning. The introduction of chelatization, hemilability, bifunctionality, shielding effects, and chirality-transfer influences the catalyst’s stability, reactivity, and selectivity, thus offering access to tailor-made systems including mono- and multidentate uNHC ligands. Based on selected examples, the structure–reactivity relationship of uNHCs employed in metal catalysts is presented. The focus is on catalytically active complexes, which either offer access to new applications or lead to significantly improved results in metal-catalyzed reactions

Molekularbiologische und mikroskopische Untersuchungen am Pathosystem Diplocarpon rosae Wolf (Sternrusstau)-Rose

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Development and preliminary validation of the Salzburg Stress Eating Scale

Stress-related eating has long been a focus of study in several disciplines. Currently available psychometric scales conflate stress-related eating with emotional eating despite that not all stress states can be subsumed under some form of specific emotion. Moreover, existing measures primarily assess increased food intake in response to emotions and stress, thus ignoring evidence of decreased food intake in response to stress. Therefore, we drew from established stress concepts to develop the first genuine stress-related eating scale (Salzburg Stress Eating Scale [SSES]) in both German and English versions. In the SSES higher scores indicate eating more when stressed and lower scores indicate eating less when stressed. In study 1 (n = 340), the German SSES was found to have a one-factor structure (a = .89). SSES scores were weakly or moderately correlated with other eating-related constructs (e.g., emotional eating, body mass index [BMI]), and weakly correlated or uncorrelated with non-eating-related constructs (e.g., impulsivity, perceived stress); in addition, women had higher scores than men. Perceived stress moderated the association between stress eating and BMI, such that higher SSES scores were significantly related to higher BMI in individuals with high perceived stress, but not in individuals with low perceived stress. In studies 2 (n = 790) and 3 (n = 331), factor structure, internal consistency, and associations with sex and BMI were replicated for both German and English versions of the SSES. Hence, the SSES represents a psychometrically sound tool for the measurement of stress-related eating

Tuning porosity and activity of microporous polymer network organocatalysts by co-polymerisation

Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asymmetric organocatalysts. Herein we show that the porous characteristics of such networks can be fine-tuned by co-polymerisation. This enables us to investigate the influence of the surface area and porosity in microporous networks on their catalytic performance. In this case, the activity of the polymers in an asymmetric hydrogenation reaction is increased by the use of polymers with higher surface areas.EC/FP7/278593/EU/Organic Zeolites/ORGZEODFG, EXC 314, Unifying Concepts in Catalysi

Pulling for pleasure? Erotic approach-bias associated with porn use, not problems

Background and Objectives: Addictive behaviors are gaining recognition in the clinical community, leading to more attention for the effects of problematic porn use. As many addictive behaviors are characterized by automatically activated approach-tendencies for disorder-relevant stimuli, we tested whether such tendencies are also present for erotic images and whether these are related to problematic porn use. Methods: Measuring approach-bias for erotic photographs, sixty-two healthy heterosexual and bisexual men completed both a relevant-feature and an irrelevant-feature approach-avoidance task (AAT). Half of participants operated a joystick as response device, the other half a keyboard. We recorded participants’ number of weekly porn-viewing sessions and symptoms of problematic porn use. Results: The irrelevant-feature AAT produced unreliable results and was not analyzed further. In the relevant-feature AAT, participants had an overall approach-bias towards erotic stimuli. Porn use frequency, but not problematic porn use, was associated with with greater erotic approach-bias. This relationship was stronger when measured with a joystick than with a keyboard. Limitations: Our design did not allow to test the causal direction of the relationship between porn use and approach-bias, and our results cannot be generalized to women, non-heterosexual men, and clinical populations. Conclusions: Similar to other addictive behaviors and substances, we found a positive relation between porn use and approach-bias. Future studies using the relevant-feature AAT will likely benefit from using the joystick rather than the keyboard.Sercan Kahveci was supported by the Doctoral College "Imaging the Mind" (FWF; W1233-B)

Zinc-zinc bonded decamethyldizincocene Zn-2(eta(5)-C5Me5)(2) as catalyst for the inter- and intramolecular hydroamination reaction

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The Zn–Zn bonded compound [(η5-Cp*)2Zn2] was investigated as catalyst for the inter- and intramolecular hydroamination reaction. High reaction rates under mild conditions were observed. This is the first application of a Zn–Zn bonded compound as catalyst.DFG, EXC 314, Unifying Concepts in Catalysi

Structure-Activity Relationships of Synthetic Analogs of Jasmonic Acid and Coronatine on Induction of Benzophenanthridine Alkaloid Accumulation in Eschscholzia californica Cell Cultures

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A facile test system based on the accumulation of benzo[c]phenanthridine alkaloids in Eschscholzia californica cell suspension culture (an indicator of defense gene activation) has been used to analyze a series of synthetic compounds for elicitor-like activity. Of the 200 jasmonic acid and coronatine analogs tested with this system, representative results obtained with 49 of them are presented here. The following can be summarized concerning structure-activity relationships: there is a large degree of plasticity allowed at the C-3 of jasmonic acid in the activation of defense genes. The carbonyl moiety is not strictly required, but exocyclic double bond character appears necessary. The pentenyl side chain at C-2 cannot tolerate bulky groups at the terminal carbon and still be biologically active. Substitutions to the C-1′ position are tolerated if they can potentially undergo β-oxidation. Either an alkanoic acid or methyl ester is required at C-1, or a side chain that can be shortened by β-oxidation or by peptidase hydrolysis. Coronatine and various derivatives thereof are not as effective as jasmonic acid, and derivatives in inducing benzo[c]phenanthridine alkaloid accumulation. Jasmonic acid rather than the octadecanoic precursors is therefore considered to be a likely signal transducer of defense gene activation in planta