Magnesium dicarboxylates promoted prenylation of phenolics that was elaborated for the total synthesis of icaritin

The prenylation of phenolic substrates promoted by Magnesium dicarboxylates was developed. Investigation of the scope demonstrated that substrats with electron-donating group(s) gave better yield than those of electron-withdrawing group(s). Although...

Synthesis and Evaluation of Antibacterial Properties of Chalcones Derived from Thiophene-2-Carbaldehyde

Chalcone is a simple chemical structure which is present in most of the naturally occurring substances. Many chalcone derivatives are synthesized by Claisen-Schmidt condensation reaction. It is a subject of great research opportunity due to numerous biological activities and convenient synthesis of chalcones. This study aims on synthesizing different α, β unsaturated ketones (chalcones) containing thiophene from thiophene-2-carbaxldehyde and different substituted acetophenones, further evaluating antibacterial activity of synthesized compounds. The synthesized compounds are characterized for their spectral study. From the antibacterial study it was observed that the compounds bearing electron withdrawing group, electron releasing group exhibited excellent to moderate antibacterial activity respectively. These results showed that chalcones incorporated with thiophene have better scopes for further development of the antimicrobial agents.

Modern Synthesis and Chemistry of Stabilized, Ketene N,O-Acetals

Ketene N,O-acetals are robust and versatile synthons. Herein, we outline the synthesis of stable ketene N,O-acetals in the twenty-first century. In addition, we review recent developments in the chemistry of ketene N,O-acetals, as it applies to the vinylogous Mukaiyama aldol reaction, electrolysis, and pericyclic transformations. While dated reports rely on in situ use, modern methods of ketene N,O-acetal synthesis are heavily oriented towards producing products with high “bench” stability; moreover, in the present century, chemists typically enhance the stability of ketene N,O-acetals by positioning an electron-withdrawing group at the β-terminus or at the N-position. As propitious substrates in the vinylogous Mukaiyama aldol reaction, ketene N,O-acetals readily provide polyketide adducts with high regioselectivity. When exposed to electrolysis conditions, the title functional group forms a reactive radical cation and cleanly couples with a variety of activated olefins. Given their electron-rich nature, ketene N,O-acetals act as facile substrates in several rearrangement reactions; further, ketene N,O-acetals reserve the ability to act as either dienophiles or dienes in Diels-Alder reactions. Lastly, ketene N,O-acetals are seemingly more stable than their O,O- counterparts and more reactive than analogous N,N- or S,S-acetals; these factors, in combination, make ketene N,O-acetals advantageous substitutes for other ketene acetal homologs.

EVALUATION OF ANTI-MICROBIAL POTENTIAL OF STRUCTURALLY MODIFIED DERIVATIVES OF LEAD COMPOUND BERBERINE ISOLATED FROM ROOTS OF BERBERIS ARISTATA

The alkaloid berberine, the chief constituent of Berberis aristata, has been reported to have antimicrobial activity associated with it. Structural changes can be made to this lead compound to try to improve its effi cacy in terms of antimicrobial activity. In the present study, attempts have been made to evaluate anti-microbial potential of structurally modifi ed derivatives of berberine. The derivatives so synthesized were characterized on the basis of spectral techniques like 1H,13C NMR, UV, IR and MASS and by comparison with standard berberine. Structure-activity relationship studies revealed that methoxyl group is pharmacophore of berberine and is thus needed to be retained in the skeleton. Further incorporation of the electron-withdrawing group has pronounced effect on the antimicrobial activity. Further attempts could be made to extend the series with the incorporation of such electron-withdrawing groups to get potent antimicrobial agents.

Electronically Excited States of Potential Interstellar, Anionic Building Blocks for Astrobiological Nucleic Acids

Functionalizing deprotonated polycyclic aromatic hydrocarbon (PAH) anion derivatives gives rise to electronically excited states in the resulting anions. While functionalization with −OH and −C2H, done presently, does not result in the richness of electronically excited states as it does with −CN done previously, the presence of dipole-bound excited states and even some valence excited states are predicted in this quantum chemical analysis. Most notably, the more electron withdrawing −C2H group leads to valence excited states once the number of rings in the molecule reaches three. Dipole-bound excited states arise when the dipole moment of the corresponding neutral radical is large enough (likely around 2.0 D), and this is most pronounced when the hydrogen atom is removed from the functional group itself regardless of whether functionalized by a hydroxyl or enthynyl group. Deprotonatation of the hydroxyl group in the PAH creates a ketone with a delocalized highest occupied molecular orbital (HOMO) unlike deprotonation of a hydrogen on the ring where a localized lone pair on one of the carbon atoms serves as the HOMO. As a result, hydroxyl functionlization and subsequent deprotonation of PAHs creates molecules that begin to exhibit structures akin to nucleic acids. However, the electron withdrawing −C2H has more excited states than the electron donating −OH functionalized PAH. This implies that the −C2H electron withdrawing group can absorb a larger energy range of photons, which signifies an increasing likelihood of being stabilized in the harsh conditions of the interstellar medium.

Tetrel Bonds between Phenyltrifluorosilane and Dimethyl Sulfoxide: Influence of Basis Sets, Substitution and Competition

Ab initio calculations have been performed for the complexes of DMSO and phenyltrifluorosilane (PTS) and its derivatives with a substituent of NH3, OCH3, CH3, OH, F, CHO, CN, NO2, and SO3H. It is necessary to use sufficiently flexible basis sets, such as aug’-cc-pVTZ, to get reliable results for the Si···O tetrel bonds. The tetrel bond in these complexes has been characterized in views of geometries, interaction energies, orbital interactions and topological parameters. The electron-donating group in PTS weakens this interaction and the electron-withdrawing group prominently strengthens it to the point where it exceeds that of the majority of hydrogen bonds. The largest interaction energy occurs in the p-HO3S-PhSiF3···DMSO complex, amounting to −122 kJ/mol. The strong Si···O tetrel bond depends to a large extent on the charge transfer from the O lone pair into the empty p orbital of Si, although it has a dominant electrostatic character. For the PTS derivatives of NH2, OH, CHO and NO2, the hydrogen bonded complex is favorable to the tetrel bonded complex for the NH2 and OH derivatives, while the σ-hole interaction prefers the π-hole interaction for the CHO and NO2 derivatives.

A Selenamorpholine and Pyrimidine-based Redox-responsive Fluorescent Probe and Its Response Mechanism

A new type of hydrogen peroxide (H2O2) fluorescent probe Pyrimidine-Se was synthesized from selenomorpholine and pyrimidinyl and the large Stokes shift (Δλ>140 nm) was exhibited. The fluorescence intensity of Pyrimidine-Se is very sensitive to pH, and its pKa value is 9.06. While the probe is reacted with H2O2, the selenomorpholine changes from Se (II) to Se (IV), which enhances the electron-withdrawing ability of the Pyrimidine-Se electron-withdrawing group. Based on this, the probe Pyrimidine-Se was used to detect H2O2 by the fluorescence spectrum. The detection limit of the probe Pyrimidine-Se was 1.3 µM. At the same time, we also found that Pyrimidine-Se displayed the reversibility back and forth between H2O2 and GSH. The reaction mechanism with H2O2 was verified by mass spectrometry and simulation on the Gaussian 09 program.

Liquid Crystals Investigation Behavior on Azo-Based Compounds: A Review

Liquid crystal is an intermediate phase between the crystalline solid and an isotropic liquid, a very common substance in our daily lives. Two major classes of liquid crystal are lyotropic, where a liquid crystal is dissolved in a specific solvent under a particular concentration and thermotropic, which can be observed under temperature difference. This review aims to understand how a structure of a certain azo compound might influence the liquid crystal properties. A few factors influence the formation of different liquid crystals: the length of the alkyl terminal chain, inter/intra-molecular interaction, presence of spacer, spacer length, polarization effects, odd-even effects, and the presence of an electron-withdrawing group or an electron-donating group. As final observations, we show the compound’s different factors, the other liquid crystal is exhibited, and the structure–property relationship is explained. Liquid crystal technology is an ideal system to be applied to products to maximize their use, especially in the electronic and medical areas.

Synthesis and Evaluation of Anticonvulsant Activity of Some Quinazoline Analogues

Aim: A new series of Quinazoline 4(3H)-one derivative were prepared by reacting quinazoline 4(3H)-one hydrazide with substituted aromatic aldehydes. Quinazoline is used as a potent pharmacological agent with various biological activities such as antimicrobial, antiviral, antitumor, convulsion, anxiety, anti-inflammatory, and analgesic. In this background, we have synthesized a series of Quinazoline 4(3H)-one derivatives (4a-4f) and screened for their anticonvulsant activity. Methods: In this work, Schiff bases were prepared by treating quinazoline 4(3H)-one hydrazide with aromatic aldehydes. Six compounds (4a-4f) were screened for anticonvulsant activity by Isoniazid (INH) and Pentylenetetrazole (PTZ) induced convulsions in mice. Results: All the compounds were given satisfactory reaction yields that representing the efficiency of the employed synthetic route. In INH induced convulsion model, delayed the onset of convulsion significantly 4a, 4b, 4d, 4e, 4f when compared to an induction control group. Whereas delayed onset of convulsion was non-significant for 4c. In PTZ induced convulsion model, delayed the onset of convulsion significantly 4a, 4d, 4e, 4f when compared to induction control group. Whereas delayed onset of convulsion was non-significant for 4b and 4c. Conclusion: This indicates the anticonvulsant activity to these derivatives which might be due to potentiating GABA activity in the CNS. This anticonvulsant activity was due to presence of electron-donating group like OH, NH2, OCH3 and electron-withdrawing group like CF3 at 2nd and 4th position of aromatic ring attached to hydrazide.

Synthesis of Mono-Carbonyl Analogues of Curcumin Assisted by Microwave Irradiation

Mono-carbonyl compounds of curcumin, especially those containing hydroxy groups at the para position in the aromatic ring flanked by an electron withdrawing group (EWG) like chlorine, are known to have anti-inflammatory, antioxidant, and antibacterial activity. This study aims to synthesize mono-carbonyl compounds of curcumin with assisted microwave synthesis and determine its toxicity. The acute toxicity assay carried out on zebrafish larvae. The results showed that the synthesis of mono-carbonyl compounds of curcumin with assisted microwave synthesis gave clean products, faster reaction rates, more product yields, economical, and environmentally friendly. The optimal synthesis results obtained at 160Watt microwave radiation energy for 10 minutes. The acute toxicity assay of HGV-6, PGV-6, and GVT-6 compounds showed low toxicity to zebrafish larvae.