Naphtho-triazoles and thienobenzo-triazoles have so far proven to be very potent inhibitors of the enzyme butyrylcholinesterase (BChE). Based on these results, in this work, new thienobenzo-thiazoles ...were designed and synthesized, and their potential inhibitory activity was tested and compared with their analogs, naphtho-oxazoles. The synthesis was carried out by photochemical cyclization of thieno-thiazolostilbenes obtained in the first reaction step. Several thienobenzo-thiazoles and naphtho-oxazoles have shown significant potential as BChE inhibitors, together with the phenolic thiazolostilbene being the most active of all tested compounds. These results are significant as BChE has been attracting growing attention due to its positive role in the treatment of Alzheimer's disease. Computational examination based on the DFT approach enabled the characterization of the geometry and electronic structure of the studied molecules. Furthermore, the molecular docking study, accompanied by additional optimization of complexes ligand-active site, offered insight into the structure and stabilizing interactions in the complexes of studied molecules and BChE.
New resveratrol–thiophene and resveratrol–maltol hybrids were synthesized as cholinesterase inhibitors and antioxidants. As with photostability experiments, biological tests also found remarkable ...differences in the properties and behavior of thiophene and maltol hybrids. While resveratrol–thiophene hybrids have excellent inhibitory and antioxidant properties (similar to the activity of reference drug galantamine), maltols have been proven to be weaker inhibitors and antioxidants. The molecular docking of selected active ligands gave insight into the structures of docked enzymes. It enabled the identification of interactions between the ligand and the active site of both cholinesterases. The maltols that proved to be active cholinesterase inhibitors were able to coordinate Fe3+ ion, forming complexes of 1:1 composition. Their formation constants, determined by spectrophotometry, are very similar, lgK = 11.6–12.6, suggesting that Fe3+ binds to the common hydroxy-pyranone moiety and is hardly affected by the other aromatic part of the ligand. Accordingly, the characteristic bands in their individual absorption spectra are uniformly red-shifted relative to those of the free ligands. The crystal structures of two new resveratrol–maltol hybrids were recorded, giving additional information on the molecules’ intermolecular hydrogen bonds and packing. In this way, several functionalities of these new resveratrol hybrids were examined as a necessary approach to finding more effective drugs for complicated neurodegenerative diseases.
In this research, the synthesis, photochemistry, and computational study of new
- and
-isomers of amino-thienostilbenes is performed to test the efficiency of their production and acid resistance, ...and to investigate their electronic structure, photoreactivity, photophysical characteristics, and potential biological activity. The electronic structure and conformations of synthesized thienostilbene amines and their photocyclization products are examined computationally, along with molecular modeling of amines possessing two thiophene rings that showed inhibitory potential toward cholinesterases. New amino-styryl thiophenes, with favorable photophysical properties and proven acid resistance, represent model compounds for their water-soluble ammonium salts as potential styryl optical dyes. The comparison with organic dyes possessing a
-aminostilbene subunit as the scaffold shows that the newly synthesized
-aminostilbenes have very similar absorbance wavelengths. Furthermore, their functionalized
-isomers and photocyclization products are good candidates for cholinesterase inhibitors because of the structural similarity of the molecular skeleton to some already proven bioactive derivatives.
A new synthetic approach is presented for the synthesis of naphthoxazoles and fused heterobenzoxazoles. The starting 5-(aryl/furyl/thienyl/pyridyl ethenyl)oxazoles are prepared from the corresponding ...α,β-unsaturated aldehydes using Van Leusen reagent in very good yields and are transformed into naphthoxazoles and fused heterobenzoxazoles on irradiation under aerobic conditions and in the presence of iodine.
To study the effects of the position of the hexatrienyl moiety on the oxazole ring, novel substituted cis/trans‐2/4/5‐(2‐vinylstyryl)oxazoles have been synthesized. These novel compounds were ...prepared by Wittig reaction from the diphosphonium salt of α,α′‐o‐xylenedibromide, formaldehyde and the corresponding 2‐methyl‐4‐, 4‐methyl‐2‐, 2‐pheny‐5‐ and 4‐methyl‐5‐oxazolecarbaldehyde, respectively. Aldehydes were synthesized by using several synthetic approaches. By applying intramolecular photocycloaddition, 2‐methyl‐4‐(2‐vinylstyryl)oxazole afforded, as major product, fused oxazoline‐benzobicyclo3.2.1octene with small quantities of 4‐(1,2‐dihydronaphthalen‐2‐yl)‐2‐methyloxazole, as electrocyclization product. Upon irradiation of 4‐methyl‐5‐(2‐vinylstyryl)oxazole, endo‐ and exo‐benzobicyclo2.1.1hexene products were formed by 2+2 cycloaddition; this was the first instance of the 1,4‐closure to the bicyclo2.1.1hexene skeleton in the 2‐, 4‐, and 5‐oxazole‐stilbene derivatives studied so far. Derivatives 2‐phenyl‐5‐ and 4‐methyl‐2‐(2‐vinylstyryl)oxazole did not react and gave only high‐weight molecular products but were crucial as a comparison in the overall mechanistic study. We have found that, depending on the position of the hexatrienyl moiety in the oxazole ring, as well as on the position of the methyl/phenyl substituents, these new vinylstyryl‐2/4/5‐oxazole derivatives show diverse photochemical behavior.
To study the effects of the position of the hexatrienyl moiety on the oxazole ring, targeted substituted cis/trans‐2/4/5‐(2‐vinylstyryl)oxazoles have been synthesized and irradiated. These new vinylstyryl‐2/4/5‐oxazole derivatives showed diverse photochemical behavior and gave new functionalized oxazole and oxazoline polycyclic products.
The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) by organophosphates (OPs) as nerve agents and pesticides compromises normal cholinergic nerve signal transduction in the ...peripheral and central nervous systems (CNS) leading to cholinergic crisis. The treatment comprises an antimuscarinic drug and an oxime reactivator of the inhibited enzyme. Oximes in use have quaternary nitrogens, and therefore poorly cross the brain–blood barrier. In this work, we synthesized novel uncharged thienostilbene oximes by the Wittig reaction, converted to aldehydes by Vilsmeier formylation, and transformed to the corresponding uncharged oximes in very high yields. Eight trans,anti- and trans,syn-isomers of oximes were tested as reactivators of nerve-agent-inhibited AChE and BChE. Four derivatives reactivated cyclosarin-inhibited BChE up to 70% in two hours of reactivation, and docking studies confirmed their productive interactions with the active site of cyclosarin-inhibited BChE. Based on the moderate binding affinity of both AChE and BChE for all selected oximes, and in silico evaluated ADME properties regarding lipophilicity and CNS activity, these compounds present a new class of oximes with the potential for further development of CNS-active therapeutics in OP poisoning.
Thermal electrocyclization reactions of benzooctatetraenes and benzodecapentaenes substituted with R=H, Cl, and methyl were studied experimentally and computationally. Methyl and unsubstituted ...benzooctatetraenes and benzodecapentaenes give the 4.2.0bicyclooctadiene products by 8π,6π-electrocyclization. Chlorine substitution led to thermal rearrangement of the initially formed 8π,6π-electrocyclization intermediates to give unprecedented products.
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Novel butadiene derivatives display diverse photochemistry and photophysics. Excitation of 2-methyl-1-(o-vinylphenyl)-4-phenylbutadiene leads to the dihydronaphthalene derivative, whereas photolysis ...of the corresponding model o-methyl analogue results in the formation of the naphthalene-like derivative, deviating from the nonmethylated analogue of the prior starting compound and producing benzobi- and -tricyclic compounds. The effect of the methyl substituents is even more dramatic in the case of the dibutadienes. The parent unsubstituted compound undergoes photoinduced intramolecular cycloaddition giving benzobicyclo3.2.1octadiene, whereas the photochemical reaction of the corresponding dimethylated derivative shows only geometrical isomerization due to the steric effect of the substituents. Methyl groups on the butadiene backbones reduce the extent of conjugation, causing a blue-shift of the characteristic absorption band. The fluorescence efficiency is dramatically decreased, as a consequence of nonplanarity and reduced rigidity of the molecules due to the crowding by the methyl and phenyl groups together. Four molecules of very similar structures show dramatically different photoinduced behavior, revealing how changes of the nature and position of the substituents are valuable in understanding the photophysics and photochemistry of these types of compounds.
The first example of thermal (8π,6π)-electrocyclisation of 1,3,5,7-octatetraene with one double bond embedded in an aromatic moiety is described. By this process, 3,4-benzo-8-substituted octatetraene ...derivatives, the cis,trans-1-(o-vinylphenyl)-4-(R = Me, Ph, 2-furyl)buta-1,3-dienes were transformed to a new endo-7-(R = Me, Ph, 2-furyl) and exo-7-(R = Me)-2,3-benzobicyclo4.2.0octa-2,4-dienes. Mechanism of reaction was also studied by DFT quantum-chemical calculations. The M06/6-311+G(d,p)//M06/6-31+G(d,p) calculations indicate that formation of the single endo-isomer in the case of phenyl and 2-furyl substituents is determined by higher activation barriers for exo-6π-electrocyclisation than for 8π-cycloreversion.
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