Search Results (17)

The 1,3-dithiolane ring has been recently rehabilitated as a chemical scaffold in drug design. However, for derivatives that are substituted in position 4, the introduction of a chiral center on the heterocycle demands the separation and characterization of the stereoisomers. We report the first chiral resolution and absolute configuration (AC) assignment for (1,4-dithiaspiro[4.5]decan-2-yl)methanol (R/S)-1, a key synthon for dithiolane-based biologically active compounds. Using (semi)preparative enantioselective HPLC, we isolated enantiomeric 1. The AC was assigned by using (+)-1 for the enantioselective synthesis of (+)-BS148, a sigma receptor modulator. An X-ray diffraction analysis established the (R)-configuration of (+)-BS148 and, by extension, of (+)-1. This method provides a reliable approach for preparing enantiopure 1,3-dithiolane scaffolds and establishes reference standards for AC determination of related compounds. Full article

A series of new quinazolin-2,4-dione derivatives incorporating amide/eight-membered nitrogen-heterocycles 2a–c, in addition, acylthiourea/amide/dithiolan-4-one and/or phenylthiazolidin-4-one 3a–d and 4a–d. The starting compound 1 was prepared by reaction of 4-(2,4-dioxo-1,4-dihydro-2H-quinazolin-3-yl)-benzoyl chloride with ammonium thiocyanate and cyanoacetic acid hydrazide. The reaction of 1 with strong electrophiles, namely, o-aminophenol, o-amino thiophenol, and/or o-phenylene diamine, resulted in corresponding quinazolin-2,4-dione derivatives incorporating eight-membered nitrogen-heterocycles 2a–d. Compounds 3a–d and 4a–d were synthesized in good-to-excellent yield through a one-pot multi-component reaction (MCR) of 1 with carbon disulfide and/or phenyl isocyanate under mild alkaline conditions, followed by ethyl chloroacetate, ethyl iodide, methyl iodide, and/or concentrated HCl, respectively. The obtained products were physicochemically characterized by melting points, elemental analysis, and spectroscopic techniques, such as FT-IR, ¹H-NMR, ¹³C-NMR, and MS. The antibacterial efficacy of the obtained eleven molecules was examined in vitro against two Gram-positive bacterial strains (Staphylococcus aureus and Staphylococcus haemolyticus). Furthermore, Computer-Aided Drug Design (CADD) was performed on the synthesized derivatives, standard drug (Methotrexate), and reported antibacterial drug with the target enzymes of bacterial strains (S. aureus and S. haemolyticus) to explain their binding mode of actions. Notably, our findings highlight compounds 2b and 2c as showing both the best antibacterial activity and docking scores against the targets. Finally, according to ADMET predictions, compounds 2b and 2c possessed acceptable pharmacokinetics properties and drug-likeness properties. Full article

Betulin and α-lipoic acid are naturally occurring substances with different biological properties. Combining two phytochemical units into a conjugate is a frequently used method to obtain new compounds with better pharmacokinetic parameters. This research concerned the preparation of lipoate derivatives of betulin using the Steglich method. Experimental lipophilicity values were determined for target compounds 6–10 by reversed-phase thin-layer chromatography. In silico methods were used to calculate the physicochemical parameters and lipophilicity of new derivatives and to determine the probable directions of biological activity. α-Lipoic acid, betulin, and lipoate derivatives 6–10 were tested for antiproliferative activity against MV4-11, A549, MCF-7, PC-3, HCT116, MiaPaca-2, and Hs294T cancer cells. 3-(5-(1,2-Dithiolan-3-yl)pentanoyl))betulin 10 showed moderate anticancer activity against MV4-11, PC-3, and HCT116, with IC₅₀ values in the range of 39.8–76.7 µM. The introduction of a dithiolate substituent at the C3 position in 28-acetylbetulin gave compound 9 the highest activity (IC₅₀ = 37.9 µM), in the ratio of biphenotypic B myelomonocytic leukemia cells (MV4-11). All lipoate derivatives were inactive towards normal cells. Full article

Quercetin (QR-3,3′,4′,5,7-pentahydroxylflavone) is very well known as a strong antioxidant with anti-inflammatory, antiviral, antineoplastic, and antithrombotic properties that can act as a free radical scavenger in human beings. It can be found in vegetables such as capers, lovage, broccoli, lettuce, spinach, onions, tea, seeds, and fruit skins. QR is recognized as one of the most important nutrients in a person’s daily diet. Lipoic acid (LA), also known as 1,2-dithiolane-3-pentanoic acid, is synthesized by animal, plant, and human cells from fatty acids and cysteine. LA is often used in the treatment of oxidative stress, diabetes, cardiovascular and hepatitis diseases, and heavy metal poisoning. In the literature, several chromatographic and optical methods have been developed in order to determine the presence of lipoic acid and quercetin with a low detection limit, but these methods have drawbacks such as sample pretreatments, the use of hazardous and expansive chemicals, and sophisticated extraction procedures. In view of this, an alternate electrochemical method for the sensitive determination of LA and QR is required. In the present work, we have developed novel electrochemical platforms for LA and QR sensing based on PEDOT-PB (poly(3,4-ethylenedioxythiophene-Prussian Blue) and PEDOT-AgNPs. Both nanocomposite materials were synthesized using a sinusoidal currents (SCs) method. The amplitude and frequency of the SCs method have been optimized. The developed electrochemical sensing platforms that use PEDOT-PB and PEDOT-AgNPs were assessed and validated for their LA and QR determination in synthetic and real samples in terms of their limit of detection, limit of quantification, and linear response range. The proposed sensing platforms ensured a comparable, fast, simple, and reliable detection of the target analytes QR and LA without sample pretreatment, as is usually required by other analytical methodologies such as chromatographic and optical methods. Full article

Thioredoxin reductase is an essential enzyme that plays a crucial role in maintaining cellular redox homeostasis by catalyzing the reduction of thioredoxin, which is involved in several vital cellular processes. The overexpression of TrxR is often associated with cancer development. A series of 1,2-dithiolane-4-carboxylic acid analogs were obtained to verify the selectivity of 1,2-dithiolane moiety toward TrxR. Asparagusic acid analogs and their bioisoters remain inactive toward TrxR, which proves the inability of the 1,2-dithiolane moiety to serve as a pharmacophore during the interaction with TrxR. It was found that the Michael acceptor functionality-containing analogs exhibit higher inhibitory effects against TrxR compared to other compounds of the series. The most potent representatives exhibited micromolar TrxR1 inhibition activity (IC₅₀ varied from 5.3 to 186.0 μM) and were further examined with in vitro cell-based assays to assess the cytotoxic effects on various cancer cell lines and cell death mechanisms. Full article

The modulation of numerous signaling pathways is orchestrated by redox regulation of cellular environments. Maintaining dynamic redox homeostasis is of utmost importance for human health, given the common occurrence of altered redox status in various pathological conditions. The cardinal component of the thioredoxin system, mammalian thioredoxin reductase (TrxR) plays a vital role in supporting various physiological functions; however, its malfunction, disrupting redox balance, is intimately associated with the pathogenesis of multiple diseases. Accordingly, the dynamic monitoring of TrxR of live organisms represents a powerful direction to facilitate the comprehensive understanding and exploration of the profound significance of redox biology in cellular processes. A number of classic assays have been developed for the determination of TrxR activity in biological samples, yet their application is constrained when exploring the real-time dynamics of TrxR activity in live organisms. Fluorescent probes offer several advantages for in situ imaging and the quantification of biological targets, such as non-destructiveness, real-time analysis, and high spatiotemporal resolution. These benefits facilitate the transition from a poise to a flux understanding of cellular targets, further advancing scientific studies in related fields. This review aims to introduce the progress in the development and application of TrxR fluorescent probes in the past years, and it mainly focuses on analyzing their reaction mechanisms, construction strategies, and potential drawbacks. Finally, this study discusses the critical challenges and issues encountered during the development of selective TrxR probes and proposes future directions for their advancement. We anticipate the comprehensive analysis of the present TrxR probes will offer some glitters of enlightenment, and we also expect that this review may shed light on the design and development of novel TrxR probes. Full article

Bayesian optimization (BO)-assisted screening was applied to identify improved reaction conditions toward a hundred-gram scale-up synthesis of 2,3,7,8-tetrathiaspiro[4.4]nonane (1), a key synthetic intermediate of 2,2-bis(mercaptomethyl)propane-1,3-dithiol [tetramercaptan pentaerythritol]. Starting from the initial training set (ITS) consisting of six trials sampled by random screening for BO, suitable parameters were predicted (78% conversion yield of spiro-dithiolane 1) within seven experiments. Moreover, BO-assisted screening with the ITS selected by Latin hypercube sampling (LHS) further improved the yield of 1 to 89% within the eight trials. The established conditions were confirmed to be satisfactory for a hundred grams scale-up synthesis of 1. Full article

The development of new bioadhesives with integrated properties remains an unmet clinical need to replace staples or sutures. Current bioadhesives do not allow electronic activation, which would allow expansion into laparoscopic and robotic surgeries. To address this deficiency, voltage-activated adhesives have been developed on both carbene- and catechol-based chemical precursors. Herein, a third platform of voltage-activated adhesive is evaluated based on lipoic acid, a non-toxic dithiolane found in aerobic metabolism and capable of ring-opening polymerization. The electro-rheological and adhesive properties of lithium, sodium, and potassium salts of lipoic acid are applied for wet tissue adhesion. At ambient conditions, potassium lipoate displays higher storage modulus than lithium or sodium salt under similar conditions. Voltage stimulation significantly improves gelation kinetics to Na- and K-lipoates, while Li-lipoate is found to not require voltage stimulation for gelation. Lap shear adhesion strength on wetted collagen substrates reveals that the synthetic metal lipoates have comparable adhesion strength to fibrin sealants without viral or ethical risks. Full article

R(+)-α-lipoic acid (RALA) is a naturally-occurring substance, and its protein-bound form plays significant role in the energy metabolism in the mitochondria. RALA is vulnerable to a variety of physical stimuli, including heat and UV light, which prompted us to study the stability of its complexes with cyclodextrins (CDs). In this study, we have prepared and purified a crystalline RALA-αCD complex and evaluated its properties in the solid state. The results of ¹H NMR and PXRD analyses indicated that the crystalline RALA-αCD complex is a channel type complex with a molar ratio of 2:3 (RALA:α-CD). Attenuated total reflection/Fourier transform infrared analysis of the complex showed the shift of the C=O stretching vibration of RALA due to the formation of the RALA-αCD complex. Raman spectroscopic analysis revealed the significant weakness of the S–S and C–S stretching vibrations of RALA in the RALA-αCD complex implying that the dithiolane ring of RALA is almost enclosed in glucose ring of α-CD. Extent of this effect was dependent on the direction of the excitation laser to the hexagonal morphology of the crystal. Solid-state NMR analysis allowed for the chemical shift of the C=O peak to be precisely determined. These results suggested that RALA was positioned in the α-CD cavity with its 1,2-dithiolane ring orientated perpendicular to the plane of the α-CD ring. Full article

α-Lipoic acid (ALA) has a chiral center at the C6 position, and exists as two enantiomers, R(+)-ALA (RALA) and S(−)-ALA (SALA). RALA is naturally occurring, and is a cofactor for mitochondrial enzymes, therefore playing a major role in energy metabolism. However, RALA cannot be used for pharmaceuticals or nutraceuticals because it readily polymerizes via a 1,2-dithiolane ring-opening when exposed to light or heat. So, it is highly desired to find out the method to stabilize RALA. The purpose of this study is to provide the spectroscopic information of stabilized RALA and SALA through complexation with cyclodextrins (CDs), α-CD, β-CD and γ-CD and to examine the physical characteristics of the resultant complexes in the solid state. The RALA-CD structures were elucidated based on the micro fourier transform infrared (FT-IR) and Raman analyses. The FT-IR results showed that the C=O stretching vibration of RALA appeared at 1717 cm⁻¹ and then shifted on formation of the RALA-CD complexes. The Raman spectra showed that the S–S and C–S stretching vibrations for RALA at 511 cm⁻¹ (S–S), 631 cm⁻¹ (C–S) and 675 cm⁻¹ (C–S) drastically weakened and almost disappeared upon complexation with CDs. Several peaks indicative of O–H vibrations also shifted or changed in intensity. These results indicate that RALA and CDs form host-guest complexes by interacting with one another. Full article

Oxidative stress is an imbalance between the production of free radicals and antioxidant defense mechanisms, potentially leading to tissue damage. Oxidative stress has a key role in the development of cerebrovascular and/or neurodegenerative diseases. This phenomenon is mainly mediated by an enhanced superoxide production by the vascular endothelium with its consequent dysfunction. Thioctic, also known as alpha-lipoic acid (1,2-dithiolane-3-pentanoic acid), is a naturally occurring antioxidant that neutralizes free radicals in the fatty and watery regions of cells. Both the reduced and oxidized forms of the compound possess antioxidant ability. Thioctic acid has two optical isomers designated as (+)- and (−)-thioctic acid. Naturally occurring thioctic acid is the (+)-thioctic acid form, but the synthetic compound largely used in the market for stability reasons is a mixture of (+)- and (−)-thioctic acid. The present study was designed to compare the antioxidant activity of the two enantiomers versus the racemic form of thioctic acid on hydrogen peroxide-induced apoptosis in a rat pheochromocytoma PC12 cell line. Cell viability was evaluated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and free oxygen radical species (ROS) production was assessed by flow cytometry. Antioxidant activity of the two enantiomers and the racemic form of thioctic acid was also evaluated in spontaneously hypertensive rats (SHR) used as an in vivo model of increased oxidative stress. A 3-h exposure of PC12 cells to hydrogen peroxide (H₂O₂) significantly decreased cell viability and increased levels of intracellular ROS production. Pre-treatment with racemic thioctic acid or (+)-enantiomer significantly inhibited H₂O₂-induced decrease in cell viability from the concentration of 50 μmol/L and 20 μmol/L, respectively. Racemic thioctic acid and (+)-salt decreased levels of intracellular ROS, which were unaffected by (−)-thioctic acid. In the brain of SHR, the occurrence of astrogliosis and neuronal damage, with a decreased expression of neurofilament 200 kDa were observed. Treatment of SHR for 30 days with (+)-thioctic acid reduced the size of astrocytes and increased the neurofilament immunoreaction. The above findings could contribute to clarify the role played by thioctic acid in central nervous system injury related to oxidative stress. The more pronounced effect of (+)-thioctic acid observed in this study may have practical therapeutic implications worthy of being investigated in further preclinical and clinical studies. Full article

Organic molecular conductors with a strongly correlated electron system, in which the itinerancy of electrons (or holes) and the electron correlation (U/W, U, the on-site Coulomb repulsion, W, the bandwidth) compete with each other, are promising candidates for achieving superconductivity and also for exploring remarkable physical properties induced by external stimuli such as pressure, light, voltage and current. Our synthetic approach to the construction of strongly correlated organic electron systems is based on chemical modifications to the donor molecule BDH-TTP [2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] capable of producing metallic CT (charge-transfer) salts stable down to low temperatures (4.2–1.5 K). This aims at enhancing the electron correlation in the itinerant electron system by decreasing the bandwidth. Chemical modifications of BDH-TTP such as ring expansion of two outer dithiolane rings, replacement of one sulfur atom in an outer dithiolane ring with an oxygen atom and introduction of two methyl substituents into an outer ditiolane ring led to BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene], DHOT-TTP [2-(1,3-dithiolan-2-ylidene)-5-(1,3-oxathiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] and DMDH-TTP [2-(4,5-dimethyl-1,3-dithiolan-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene], respectively. In this review, the physical properties and the crystal and electronic structures of molecular conductors derived from these donor molecules will be described. Full article