Királis koronaéterekkel katalizált enantioszelektív szintézisek és ''deracemizációs'' reakciók vizsgálata = Investigation of enantioselective synthesis and deracemization reactions by chiral crownethers

A monoszacharidokból felépülő királis koronaéterek aszimmetrikus indukciót képesek kifejteni bizonyos reakciókban, ha királis fázistranszfer katalizátorként alkalmazzuk azokat. Új királis metil-α-D-glükopiranozid- és α-D-mannopiranozid-alapú monoaza-15-korona-5 típusú étereket szintetizáltunk, melyek korona-gyűrűjében oxigén, kén vagy nitrogén atomok voltak, valamint foszfor atomot tartalmazó 17-korona-7 típusú vegyületeket. Vizsgáltuk a makrociklusok alkáli fém kationokkal mutatott komplexképző képességét. Néhány koronaéter katalizátorként jelentős aszimmetrikus indukciót eredményezett: a 2-nitropropán kalkonra és kalkon analgonokra történő Michael addíciójában (80-94 % ee), kalkonok terc-butil-hidroperoxiddal történő epoxidációs reakciójában (75-94 % ee) és α-klór-acetofenon szubsztituált benzaldehidekkel lejátszódó Darzens kondenzációjában (60-72 % ee) kétfázisú reakciókban. A katalizátort felépítő szénhidrát királis tulajdonsága jelentősen befolyásolja a kémiai termelést és az enantioszelektivitást. Például, amíg a D-glükopiranozidból felépülő koronaéterek a 2R,3S konfigurációjú epoxiketon keletkezését preferálták (max. 94 % ee), addig a D-mannopiranozid-alapú katalizátorok az ellentétes, 2S,3R konfigurációjú termék keletkezését segítették elő (max. 82 % ee) a kalkon epoxidációs reakciójában. Az új epoxi-ketonok abszolút konfigurációját CD spektroszkópiásan határoztuk meg. A reakciók mechanizmusát molekulamodel számításokkal bizonyítottuk. | The chiral crown ethers incorporating monosaccharide moiety in their ring, are able to general asymmetric induction as chiral phase transfer catalysts in certain reactions. New chiral methyl-α-D-glucopyranoside- and methyl-α-D-mannopyranoside-based monoaza-15-crown-5 ethers having oxygen, sulphur or nitrogen atoms in the crown ring, and 17-crown-7 type ethers containing a phosphorus atom have been synthesized. The complex forming ability of the compounds with alkali metal and ammonium cations was investigated. Some crown ethers resulted in significant asymmetric induction as catalysts in Michael addition of 2-nitropropane to substituted chalcones and heteroaromatic chalcone analogues (80-94 % ee), in the epoxidation of the different chalcones with tert-butylhydroperoxide (75-94 % ee) and in the Darzens condensation of phenacyl chloride with substituted benzaldehydes (60-72 % ee). The chiral nature of the carbohydrate in the catalyst, the quality of the side arm attached to the nitrogen atom had a significant effect on the enantioselectivity. For example the use of D-glucopyranoside-based crown ethers promoted the formation of epoxyketone with 2R,3S configuration (94 % ee), at the same time, the D-mannopyranoside-based catalyst preferred the formation of 2S,3R enantiomer (82 % ee) in the epoxidation of chalcone. The absolute configurations of epoxyketones were determined by CD spectroscopy. The mechanism of the reactions was evaluated by molecule modeling calculations

Green chemical approaches and tools in the development of environmentally friendly synthetic methods

Addressing the recommendations of the 12 basic lows of green chemistry, the microwave technique was utilized in phospha-Mannich, Diels-Alder and inverse Wittig type reactions, moreover under solventless conditions. In the phase transfer catalysed alkylation of CH-acidic compounds, the quaternary onium salts could be substituted by MW irradiation. The effect of chiral phase transfer catalysts was compared on suitable, potentially enantioselective model reactions. Mono- and bidental P-ligands were developed to make available novel platinum complexes that can be useful as catalysts. Finally, esterifications including diesterifications were studied by in situ Fourier Transform IR spectroscopy

The Impact of Green Marketing on Consumer Behavior in the Market of Palm Oil Products

The aim of the article is to examine the impact of green marketing on consumer behavior in the market for products containing palm oil. The first chapter addresses the theoretical approach—the impact of green marketing on consumer behavior. We considered a questionnaire survey to be the most appropriate method to conduct our research. In order to test our hypotheses, we applied Crosstab and Pearson’s chi-square test. The strength of the relationship between the variables was measured using Cramer’s V. The third chapter presents the research results based on the processed information of 527 obtained datasheets from the respondents. The data were collected from Slovak consumers in the summer of 2021. Hypotheses H1 (There is a significant relationship between the opinion of the consumer regarding purchasing products containing palm oil and the knowledge that the product does contain palm oil.) and H2 (There is a relationship between the consumer willingness to refuse the purchase of certain products if it has negative impact on the environment and the generational group the consumer belongs to.) were approved, however the relationship proved to be weak in both cases. The research makes it clear that the majority of consumers do not spend time reading descriptions on product packaging. It might be helpful for companies to make it clear and visible on the packaging that their product does not contain palm oil, informing the consumer and influencing them with the negative emotional message of the advert. The obtained research results are useful both for the producers and the customers

Reactivity Models of Hydrogen Activation by Frustrated Lewis Pairs: Synergistic Electron Transfers or Polarization by Electric Field?

Two alternative qualitative reactivity models have recently been proposed to interpret the facile heterolytic cleavage of H(2) by frustrated Lewis pairs. Both models assume that the reaction takes place via reactive intermediates with preorganized acid/base partners; however, they differ in the mode of action of the active centers. In the electron transfer (ET) model, the hydrogen activation is associated with synergistic electron donation processes with the simultaneous involvement of active centers and the bridging hydrogen, showing similarity to transition-metal-based and other H(2)-activating systems. In contrast, the electric field (EF) model suggests that the heterolytic bond cleavage occurs as a result of polarization by the strong electric field present in the cavity of the reactive intermediates. To assess the applicability of the two conceptually different mechanistic views, we examined the structural and electronic rearrangements as well as the electric fields along the H2 splitting pathways for a representative set of reactions. The analysis reveals that electron donations developing already in the initial phase are general characteristics of all studied reactions, and the related ET model provides qualitative interpretation for the main features of the reaction pathways. On the other hand, several arguments have emerged that cast doubt on the relevance of electric field effects as a conceptual basis in FLP-mediated hydrogen activation

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Signalling Enhances Osteogenesis in UMR-106 Cell Line

Presence of the pituitary adenylate cyclase-activating polypeptide (PACAP) signalling has been proved in various peripheral tissues. PACAP can activate protein kinase A (PKA) signalling via binding to pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1), vasoactive intestinal polypeptide receptor (VPAC) 1 or VPAC2 receptor. Since little is known about the role of this regulatory mechanism in bone formation, we aimed to investigate the effect of PACAP on osteogenesis of UMR-106 cells. PACAP 1-38 as an agonist and PACAP 6-38 as an antagonist of PAC1 were added to the culture medium. Surprisingly, both substances enhanced protein expressions of collagen type I, osterix and alkaline phosphatase, along with higher cell proliferation rate and an augmented mineralisation. Although expression of PKA was elevated, no alterations were detected in the expression, phosphorylation and nuclear presence of CREB, but increased nuclear appearance of Runx2, the key transcription factor of osteoblast differentiation, was shown. Both PACAPs increased the expressions of bone morphogenetic proteins (BMPs) 2, 4, 6, 7 and Smad1 proteins, as well as that of Sonic hedgehog, PATCH1 and Gli1. Data of our experiments indicate that activation of PACAP pathway enhances bone formation of UMR-106 cells and PKA, BMP and Hedgehog signalling pathways became activated. We also found that PACAP 6-38 did not act as an antagonist of PACAP signalling in UMR-106 cells