Synthesis of Pyrrolizinone and Pyrrolizino[1,2-a]pyrrolizin-5-one Skeletons Starting From Pyrrole Through A Single-Step and Catalyst-Free Approach

1H-Pyrrole and lactone-type 2,3-furandione derivatives were reacted in anhydrous diethyl ether (Et2O) at room temperature, and then one of the important alkaloid skeletons, pyrrolizinone derivatives, were synthesized via a single step and catalyst-free approach. Various pyrrolizinone derivatives having various substituents such as phenyl, substituted phenyl, thiophene, -CF3, naphthalene, bi-phenyl, ester, and oxalate were yielded. Employing an equimolar pyrrole molecule yielded pyrrolizinones, while using an excess molar of pyrrole yielded pyrrolizino[1,2-a]pyrrolizin-5-one which is not present in the literature. Yield of purified molecules was up to 91%. One of the cyclization processes was carried out on a gram-scale, yielding 0.952 g (71%).

Synthesis of spiroindolenine-cyclopentenedione skeletons and their chemical behaviours: the first example of a lactone-type spiroindolenine structure

A manageable, one-pot, and high-yield protocol for synthesising highly reactive spiroindolenine derivatives is reported. Spiroindolenines are furnished by a reaction between DCC (dicyclohexylcarbodiimide) and indole-3-butenoic acid derivatives. The protocol proposed here involves the construction of a carbon-carbon bond through intramolecular domino cyclisation. The reaction mechanism for spirocyclisation is discussed; both NMR and X-ray analysis were used to verify the structure of spiroindolenine. The applied strategy allowed the formation of spiroindolenine with a dione substructure, which is an unknown compound with a spirocyclic nucleus. Further reactions of spiroindolenines with di-amines, a primary amine, and alcohol have been reported, and new types of indole derivatives, such as indoloquinoxalines, where the spirocentre atom undergoes a nucleophilic attack, are yielded.

A novel class for carbonic anhydrases inhibitors and evaluation of their non-zinc binding

In this study, 23 different imidazole derivatives were synthesized, and the inhibitory properties of these derivatives against carbonic anhydrase I and II isoenzymes were investigated for the first time. The inhibition concentrations of the imidazole derivatives were found to be in the range of 2.89-115.5 nM. Docking studies examined the binding properties of the imidazole derivatives, and the structure-activity relationship is discussed. Theoretical calculations showed that the binding mode of the imidazole ring was non-zinc binding.

Excited State Intramolecular Proton Transfer (ESIPT)-Based Sensor for Ion Detection

C-2 and C-5 substituted imidazole skeleton was synthesized through a one-pot two-step strategy. Synthesized molecule emits the light on ESIPT (excited-state intramolecular proton transfer). This molecule was utilized for its proton donor ability, and we have observed that fluoride and cyanide ions can be detected selectively. Different cations and anions were selected to observe the response of the synthesized molecule. However, there were not any fluorometric and colorimetric response except for fluoride and cyanide ions. Detection limits of fluoride and cyanide ions were found to be 9.22 μM and 11.48 μM, respectively. ¹H-NMR spectra for the solution of the sensor and TBAF (tetrabuthylammoniumfluoride) were used for the identification of [L]^-[HF₂]^- species. 3 equiv. TBAF saturated the solution of the sensor in d₆-DMSO, and some of the proton resonances shifted to upfield due to the through-bond effect. The disappearance of NH proton with 0.5 equiv. TBAF or TBACN (tetrabuthylammoniumcyanide) showed that there was a proton abstraction by fluoride and cyanide ions, instead of the hydrogen bond. Solid-state application was utilized, and paper test strips were applied. Emission differences emerged when the sensor loaded strips were reacted with TBAF. Time resolved experiments revealed that solution of the sensor and TBAF in DMSO have multiexponential decay, and one of the lifetime was measured as 13.4 ns.

A new synthetic approach for pyrazolo[1,5-a]pyrazine-4(5H)-one derivatives and their antiproliferative effects on lung adenocarcinoma cell line

Starting from the 3,5-dimethyl pyrazole ring and acetophenone derivatives, five different N-propargylated C-3 substituted pyrazoles were obtained. These derivatives were reacted with different amine derivatives using Cs₂CO₃ in methanol and 11 different pyrazolo [1,5-a] pyrazine-4(5H)-one derivatives were obtained, which are not found in the literature. The cytotoxic effects of these derivatives in the A549 cell line were investigated. The 160 µM concentration of two derivatives was found to increase cell death rate to 50%, and two derivatives increased cell death rate by up to 40%. The structure-activity relationship (SAR) study revealed an amide group with a long alkyl chain and benzene ring with a p-CF₃ group could be important for efficiency. With theoretical ADMET studies of pyrazolopyrazine derivatives, pharmacokinetic phases were predicted to be suitable.

Copper-Catalyzed Synthesis of Fused Imidazopyrazine N-Oxide Skeletons

N-Propargyl-2-aroylimidazoles synthesized and converted into the corresponding ketoximes. Under various conditions, several mono- and diketoxime imidazole derivatives were formed by converting the carbonyl or carbonyl and propargyl groups into oxime groups. N-Propargyl monooxime imidazole derivatives were cyclized by treatment with CuI to give various imidazopyrazine N-­oxides. Several copper salts, such as CuOAc, CuSO4, and CuOTf, formed the same cyclization product. This cyclization reaction occurred only in the presence of Cu(I) or Cu(II) salts; other transition metals such as Au, Ag, In, and Fe did not yield cyclic products. The nucleus-independent chemical shift method was used to calculate the aromaticity of the bicyclic rings.

Synthesis of novel imidazopyridines and their biological evaluation as potent anticancer agents: A promising candidate for glioblastoma

Novel imidazopyridine derivatives were synthesized according to a very simple protocol and then subjected to cytotoxicity testing against LN-405 cells. Two of the compounds exhibited antiproliferative effects on LN-405 cells at 10 and 75 µM and were selected as lead compounds for further study. Safety experiment for lead compounds on WS1 was carried out and IC₅₀ values were calculated as 480 and 844 µM. LN-405 cell line were incubated with the lead compounds and then tested for DNA damage by comet assay and effects on cell cycle using flow cytometry. The results of these two tests showed that both lead compounds affected the G0/G1 phase and did not allow the cells to reach the synthesis phase. The log BB (blood-brain barrier) and Caco-2 permeability of the synthesized molecules were calculated and it was shown that imidazopyridine derivatives taken orally are likely to pass through gastrointestinal membrane and the blood-brain barrier.

Indole-containing new types of dyes and their UV-vis and NMR spectra and electronic structures: Experimental and theoretical study

Indole containing dyes were synthesized via a simple method with high yield. These molecules have different colors and UV-vis spectra of them were recorded. Impact of solvents on absorbances was investigated and it was observed that basic solvent such as DMF and pyridine have blue shift. TD-DFT calculations were done and results were compared with experimental data. NMR data of molecules were analyzed and tautomeric forms of colorants and their ratio were determined. It was find out that two tautomers might be formed in solution, called indole and indolenine form. HOMO-LUMO and energy gaps were calculated and plotted. Furthermore, molecular electrostatic potentials were simulated to find out electrophilic and nucleophilic regions.

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

Various N-propargylpyrrole and indolecarboxylic acids were efficiently converted into 3,4-dihydropyrrolo- and indolo-oxazin-1-one derivatives by a gold(III)-catalyzed cyclization reaction. Some of the products underwent TFA-catalyzed double bond isomerization and some did not. Cyclization reactions in the presence of alcohol catalyzed by Au(I) resulted in the formation of hemiacetals after cascade reactions.

Design and synthesis of pyrrolotriazepine derivatives: an experimental and computational study

The pyrrole derivatives having carbonyl groups at the C-2 position were converted to N-propargyl pyrroles. The reaction of those compounds with hydrazine monohydrate resulted in the formation of 5H-pyrrolo[2,1-d][1,2,5]triazepine derivatives. The synthesis of these compounds was accomplished in three steps starting from pyrrole. On the other hand, attempted cyclization of a pyrrole ester substituted with a propargyl group at the nitrogen atom gave, unexpectedly, the six-membered cyclization product, 2-amino-3-methylpyrrolo[1,2-a]pyrazin-1(2H)-one as the major product. The expected cyclization product with a seven-membered ring, 4-methyl-2,3-dihydro-1H-pyrrolo[2,1-d][1,2,5]triazepin-1-one was formed as the minor product and was converted quantitatively to the major product. The formation mechanism of the products was investigated, and the results obtained were also supported by theoretical calculations.