Michal Kohout

University of Chemistry and Technology | VSCHT · Department of Organic Chemistry

In the past two decades, supercritical fluid chromatography has evolved from a niche application to a comprehensive technology and a fully-fledged alternative to conventional high-performance liquid chromatography. Due to high miscibility of supercritical carbon dioxide with common organic solvents, the supercritical fluid chromatography offers a b...

Nanoparticles serving as a multifunctional and multiaddressable dopant to modify the properties of liquid crystalline matrices are developed by combining cobalt ferrite nanocrystals with organic ligands featuring a robust photosensitive unit and a source of chirality from the natural pool. These nanoparticles provide a stable nanocomposite when dis...

New psychoactive substances and among them synthetic cathinones represent a significant threat to human health globally. However, within such a large pool of substances derived from a natural compound ((S)-cathinone), substances with important pharmaceutical uses can be identified, as already documented by bupropione. Therefore, this work aimed to...

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Light polarization rotations, created by applied optical field, are examined experimentally and theoretically in a photosensitive chiral nematic fluid. The polarization rotation of the transmitted beam is initiated by illuminating the sample with uniform UV light. The operation is tunable and reversible, depending on the UV intensity. It was reveal...

The emergence of new synthetic cathinones continues to be a matter of public health concern. In fact, already known products (drugs) are being rapidly replaced by new structurally related alternatives, whereby modifications in the basic cathinone structure are used by manufacturers to circumvent the legislation. On the other hand, some derivatives...

Tuning the frontier orbital energies is the way to control nature of majority charge carriers. Therefore, among sensing materials operating in the real atmosphere, the fluorinated compounds are under the...

Recent liquid-crystalline (LC) research is focused on structurally new molecular systems distinct from simple nematic or smectic phases. Sophisticated molecular shape may reveal structural complexity, combining helicity and polarity. Achiral...

Recently, the number of structural modifications of synthetic cathinones has been growing making them the second largest group of new psychoactive substances in Europe. Although they are abused because of their various psychoactive effects, some compounds from this group also serve as pharmaceuticals. Since synthetic cathinones are chiral molecules...

Inherently chiral compounds, such as calixarenes, are chiral due to a nonplanar three-dimensional (3D) structure. Determining their conformation is essential to understand their properties, with nuclear magnetic resonance (NMR) spectroscopy being one applicable method. Using alignment media to measure residual dipolar couplings (RDCs) to obtain str...

Methoxphenidine was originally patented for its properties to treat neurotoxic injury. However, due to the side effects, it failed to become pharmaceutic and later reappeared on the black market among...

Aim Novel benzodiazepines, emerged on the recreational drug market in past few years, have caused serious problems in many countries, including intoxications and fatalities. Not only, that limited information is still available on their dosage, the situation may be even more complicated if a combination of these designer drugs occurs. Method For i...

Aim Recently, the number of new psychoactive substances (NPS), which are sold as legal alternatives to conventional or misused drugs, has been growing on the market. Via small chemical modifications in the basic structure of the already banned substances, new derivatives are made. Although they pose a real threat to human health, they do circumvent...

Aim Methoxphenidine (MXP) belongs among dissociative anesthetics from the group of new psychoactive substances. According to the unofficial user experiences, MXP is less active than common dissociative anesthetics like ketamine, yet, several intoxications were associated with this substance up to this date. Within our previous work, we discovered t...

In this paper, we have applied a holographic time-of-flight technique with a nanosecond laser pulse to perform time-resolved measurements of optically induced gratings in bent-core nematics formed by a new kind of liquid crystal (LC). The effects of the electric field, laser pulse energy, temperature, and light intensity pattern on the photocharge...

Optically active linear polyimides and hyperbranched poly (amic acid–imide) were prepared by using procedures varying in particular in the maximum temperature employed in their synthesis. The two types of linear polyimides were based on 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 1,2‐diaminocylohexane enantiomers or 4,4′‐(hexafluoroisop...

Chiral zwitterion ion exchangers represent efficient chiral stationary phases for stereoselective resolution of various analytes including chiral acids, bases, and zwitterions. In this contribution, we have focused on utilization of chiral zwitterionic sorbents, denoted as ZWIX (+A) and ZWIX (−A). These are analogical chiral systems to commercially...

Cholesteric liquid crystals reflecting circularly polarised light are promising materials for creating flexible and compact polarisers. One of the issues of these systems is the narrow width of the photonic stop band. The range of selective light reflection can be increased by creating a gradient of the cholesteric pitch in the process of photopoly...

We present a new type of light responsive self-assembling structures based on a spiropyran photoswitchable unit. The spiropyran central part was modified by functional groups, which enabled the connection of two structurally different elongating parts. Two series of compounds were prepared with reversed orientation of the ester as a linkage group i...

Background and purpose Deschloroketamine (DCK), a structural analogue of ketamine, has recently emerged on the illicit drug market as a recreational drug with a modestly long duration of action. Despite it being widely used by recreational users, no systematic research on its effects has been performed to date. Experimental approach Pharmacokineti...

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables fast (E)-to-(Z)-isomerization upon irradiation...

Amino acid analysis (AAA) is of central importance for the characterization of the amino acid composition of proteins, peptides, pharmaceutical formulations, dietary supplements, in bioanalysis and metabolomics. Common methodologies are based on achiral assays and hence do not consider distinction of D- and L-amino acid enantiomers. This may be mis...

In the continuation of our effort to synthesize highly dedicated strong cation exchanger, we introduce four chiral stationary phases based on a laterally substituted naphthalene core featuring chiral 2‐aminocyclohexansulfonic acid as the chiral cation‐exchange unit. The selectors were modified with two different terminal units, which enabled immobi...

In this paper, we report on the photoisomerization process of three series of photosensitive bent-core liquid crystals with a lateral chlorine atom in the central resorcinol core and various linkers. The effect of linkers, such as benzoate ester, biphenyl, cinnamate, Schiff base and stilbene on the photoisomerization and thermal back relaxation hav...

A set of new mixed-mode ion-exchange stationary phases is presented. The backbone of organic selectors is formed by a linear hydrocarbon chain, which is divided into two parts of various lengths by a heteroatom (oxygen or nitrogen). In all studied cases, there is a sulfonic acid moiety as the terminal group. Therefore, selectors bearing oxygen gave...

One of the most frequently utilized liquid crystalline (LC) materials is a rod-like (calamitic) compound 4-cyano-4′-pentylbiphenyl (5-CB). The main objective of this work is to enhance its functionality by introducing a photoresponsive diazenyl spacer in the aromatic core and replace the non-chiral pentyl chain with various chiral alkyl carboxylate...

New psychoactive substances (NPSs) have become a popular alternative to illicit drugs of abuse. However, to determine their metabolic pathways in the human organism, a detailed knowledge of their structure is crucial. Here, we present a comprehensive spectroscopic structural study of the synthetic cathinones (clephedrone, flephedrone, brephedrone)...

We present a new series of bent-core liquid crystals possessing a lateral substituent in the apex position of the central core and a terephthalate connecting unit in one elongating side arm. The synthesised materials have been studied by polarising optical microscopy, differential scanning calorimetry, dielectric spectroscopy and X-ray diffraction....

The preparation of inherently chiral rigidified calix[4]arenes with an intact cavity is a synthetic challenge due to the complicated synthesis of the starting compounds. Here, we report on a novel strategy for bridging the upper rim of calix[4]arenes consisting in carbonyl group formation and subsequent "extension" into a two-atom bridge using corr...

A composite membrane comprising a microfiber thermoplastic layer of a mixture of polyethylene and polypropylene and a nanofiber layer of a polymer selected from the group consisting of polyamides, polyurethanes, polyureas and mixtures thereof, which together form a laminate, and a polymer deposited on fibers and containing chiral monomer units deri...

In this work, the plasmon-active gold grating functionalized by homochiral metal-organic frameworks (HMOF) L- or D-MOF-6 was proposed as unprecedent tool for enantio-selective SERS-based discrimination. The gold grating surface possesses the homogeneous distribution of plasmon intensity along the active sample area, responsible for excitation of co...

We present the synthesis and mesomorphic properties of the new series of bent-core liquid crystals based on 3-hydroxybenzoic acid bearing a lateral substituent in the apex position. Four different substituents of various sizes and electronic properties have been used. We have found that only compounds substituted with fluorine are mesogenic and exh...

We have synthesised several series of dialkoxy-terminated biphenyl benzoates with lateral substituents (X = F, Cl) in the vicinity of the ester linking group, varying the length of the terminal alkyl chains. The aim was to study mesomorphic properties of these new compounds and compare them with the previously reported analogous phenyl biphenylcarb...

The meta- and para-substituted aminocalix[4]arenes immobilized in the cone conformation were acylated to yield corresponding acyl amides. Subsequent cyclization with aryl or alkyl cyanides afforded the expected quinazolines only in the case of para-substituted series while only complex reaction mixtures were obtained for the meta-substituted analog...

We present two isomeric series of photosensitive bent-core liquid crystals possessing a lateral chlorine atom in the central resorcinol unit and various linking units in the side arms. With the aim to tune properties of the nematic phase, we have varied the type of the linking unit in the lengthening arm with rising rigidity from benzoate ester, bi...

A series of unique composite membranes formed from a nano&micro fibrous material with different amounts of a chiral selector was used for separation of chiral drugs. The membrane performances were demonstrated through sorption tests, wherein they were soaked in an aqueous solution of racemic D,L-tryptophan (a model chiral drug). The changes in conc...

Nowadays, there is a strong need for replacement of racemates by enantiomerically pure drugs. Enantioseparation on polymer membranes seems to be one of the promising and economically feasible technologies for this purpose. As a material for membrane construction, linear polymer molecules bearing covalently bonded chiral selectors are very promising...

Chromatographic performance of a chiral stationary phase is significantly influenced by the employed solid support. Properties of the most commonly used support, silica particles, such as size and size distribution, and pore size are of utmost importance for both superficially porous particles and fully porous particles. In this work, we have focus...

Meta/meta- and meta/para-disubstituted organomercury calix[4]arenes in the cone conformation were transformed into corresponding amino derivatives. Acylation and subsequent intramolecular cyclization using the Bischler-Napieralski reaction provided, in the case of the meta/meta-series, double bridged calixarenes possessing seven membered rings on t...

Zwitterionic chiral ion-exchange selectors (ZWIX) obtained by conjugation of quinine and 2-aminocyclohexanesulfonic acid via a carbamate bond were immobilized on three different silica particle types, viz. 120 Å 3 μm fully porous particles (FPP), 200 Å 3 μm FPP and 160 Å 2.7 μm superficially porous particles (SPP). Selector densities were determine...

Nitrosobenzene has been demonstrated to participate in the Mitsunobu reaction in an analogous manner to dialkyl azodicarboxylates. The protocol using nitrosobenzene and triphenylphosphine (1:1) under mild conditions (0 °C) provides the ester derivatives of aliphatic and aromatic acids using various alcohols in moderate yield and with good enantiose...

Liquid crystals (LCs) are among the most prominent materials of the current information age, mainly due to their well-known application in liquid crystal displays (LCDs). Their unique electro-optical properties stem from their ability to form organised structures (mesophases) on the transition from solid state to isotropic liquid. Molecules of LCs...

Purpose The growing availability of new psychoactive substances with unknown toxicity is alarming all over the world. The simplicity of acquiring these drugs of abuse from internet markets has caused an increase in the total number of seizures. We present the first systematic spectroscopic study of methylone and pentylone, which are in the class of...

A new photoresponsive bent‐core nematic (BCN) material, which exhibits flexoelectric domains (FDs) driven by electric field, is reported. Unexpectedly, it is found that the morphologies of FDs can be controlled by irradiation with light fields. This light tunability is ascribed to the photoisomerization effect of the azo moiety within the BCN molec...

Phenoxathiin-based thiacalix[4]arene, accessible via acid-catalysed rearrangement of the starting spirodienone derivative, was subjected to the oxidation of sulfur bridging groups. Using the excess of the oxidation agent, systems bearing four sulfonyl groups or three sulfonyl and one sulfoxide group are available in high yields, depending on the re...

A new series of photosensitive azo materials possessing a chiral alkyl lactate moiety and terminal n-alkyl carboxylate unit close to the azo group has been synthesized and studied. The length of the n-alkyl carboxylate chain has been systematically varied in order to establish the effect of the molecular structure on the self-assembling behaviour....

In this study, we aim to determine differences in cytotoxicity of racemic deschloroketamine and its enantiomers. The synthesized racemate of this recently rediscovered and abused dissociative anaesthetic was resolved by chiral HPLC and the absolute configuration of the enantiomers was assigned using a combination of circular dichroism methods and s...

Triphenylphosphine (Ph3P) activated by various electrophiles (e.g., alkyl diazocarboxylates) represents an effective mediator of esterification and other nucleophilic substitution reactions. We report herein an aza-reagent-free procedure using flavin catalyst (3-methyl riboflavin tetraacetate), triphenylphosphine, and visible light (448 nm), which...

Recent advancements in particle design are common in reversed-phase liquid chromatography (RPLC), but in chiral separations their use is still sporadic in commercially available chiral stationary phases (CSPs). Due to reported lower mass transfer resistance, they might be a promising opportunity to increase efficiency and reduce time of analysis si...

Recently, there has been a worldwide substantial increase in the consumption of new psychoactive substances (NPS), compounds that mimic the structure of illicit drugs, such as amphetamines or ecstasy. The producers try to avoid the law by a slight modification of illicit structures, thereby developing dozens of temporarily legal NPS every year. The...

In the enantiomeric separation of highly polar compounds, a traditionally challenging task for high-performance liquid chromatography, ion-exchange chiral stationary phases have found the main field of application. In this contribution, we present a series of novel anion-exchange-type chiral stationary phases for enantiomer separation of protected...

In this pilot study, we present novel bifunctional silica gel-immobilized materials applicable as heterogeneous organocatalysts and stationary phases in HPLC. The materials provided high stereoselectivity in both batch and continuous flow catalysis of a model Michael addition (cyclohexanone to (E)-β-nitrostyrene). In the batch reaction, the catalys...

The enantiomeric pairs of cis and trans stereoisomers of cyclic β-aminohydroxamic acids and their related cis and trans cyclic β-amino acids containing two chiral centers were directly separated on four structurally related chiral stationary phases derived from quinine and quinidine modified with (R,R)- and (S,S)-aminocyclohexanesulfonic acids. App...

The enantiomers of trans-paroxetine (the selectand) were separated on four chiral stationary phases incorporating either quinine [ZWIX(+), ZWIX(+A)] or quinidine [ZWIX(–), ZWIX(–A)] and (R,R)-aminocyclohexanesulfonic acid [in ZWIX(–), and ZWIX(+A)] or (S,S)- aminocyclohexanesulfonic acid [in ZWIX(+), and ZWIX(–A)] chiral selectors. The zwitterion n...

Major differences in the chromatographic performance of a zwitterion ion-exchange type (ZWIX) chiral stationary phase (CSP) in supercritical fluid chromatography (SFC) and high-performance liquid chromatography (HPLC) have been observed. To explain these differences, transition from HPLC to SFC conditions has been performed. The amount of a protic...

Photosensitive liquid crystals are of contemporary interest not only from the scientific point of view but also for various applications. Herein we report the first photosensitive materials based on laterally substituted 3-hydroxybenzoic acid. The molecular self-assembly of these new materials was characterized using different physical techniques i...

X-ray powder diffraction data, unit-cell parameters, and space group for S -2-(methylamino)-2-phenylcyclohexan-1-one hydrochloride, C 13 H 18 ClNO, are reported [ a = 6.578 (1) Å, b = 13.250 (2) Å, c = 15.096 (2) Å, β = 91.619 (3)°, unit-cell volume V = 1315(1) Å ³ , Z = 4, and space group P 2 1 ]. All measured lines were indexed and are consistent...

The mercuration of calix[4]arene immobilized in the cone conformation allowed the introduction of an amino group at the meta position of the basic skeleton. Acylation and subsequent intramolecular Bischler-Napieralski-type cyclization led to a novel type of bridged calixarene containing a seven-membered ring. These compounds with an enlarged and ri...

We present enantioseparation of a series of racemic sulfoxides on three different amylose-based polysaccharide columns. Two of them have the amylose units modified with dimethylphenyl carbamoyl groups (Chiralpak AD-H and Chiralpak IA), while the third one possesses a carbamoyl moiety with an additional chiral centre (Chiralpak AS-H). The enantiosep...

The partial S-oxidation of all four basic conformations of thiacalix[4]arene was carried out using NaBO3·4H2O as the oxidizing agent. It was found that despite the possible formation of many regio- and stereoisomers, the reactions leading to mono- or disulfoxides were highly regio- and stereoselective depending on the starting conformation. Our res...

The usefulness of flavin-based aerial photooxidation in esterification under Mitsunobu reaction conditions was demonstrated, providing aerial dialkyl azodicarboxylate recycling/generation from the corresponding dialkyl hydrazine dicarboxylate. Simultaneously, activation of triphenylphosphine (Ph3P) by photoinduced electron transfer from flavin allo...

We report the synthesis and study of the mesomorphic behaviour for a series of bent-core materials based on 2-substituted 3-hydroxybenzoic acid as a central unit. Properties of the studied compounds are tuned by lateral substitution (F, Cl, CH3, NO2 and CN) in the position 2 of 3-hydroxybenzoic acid and by the length of the terminal alkyl chain. Al...

Herein, we present a simple and affordable green synthesis of a nanocomposite material consisting of copper nanoparticles stabilized in a polyvinyl alcohol-glycerol matrix. TEM, UV-Vis and XRPD (X-ray Powder Diffraction) techniques were used to characterize the nanoparticles; properties of the polymer matrix were studied by NMR, IR and Raman spectr...

We have prepared and studied new series of bent-core liquid crystals based on laterally substituted 3-hydroxybenzoic acid. The physical properties of the materials were tuned by the type of lateral substitution in the vicinity of the carboxylic unit. Further modification was achieved by reorientation of connecting ester linkages in the elongating s...

Two series of new liquid crystalline lactic acid derivatives with a terminal ester group have been synthesised. The effect of this ester unit and the length of its alkyl chain on the mesomorphic and dielectric properties of the compounds exhibiting a broad temperature range of chiral smectic phases have been studied. We found that the mesomorphic b...

Abstract The enantiomers of trans-paroxetine were separated on four chiral stationary phases (CSPs) based on chiral zwitterionic Cinchona alkaloids fused with (R,R)- or (S,S)-trans-2-aminocyclohexanesulfonic acid. The enantioseparations were carried out in polar-ionic or in hydro-organic mobile phases with MeOH/THF, MeCN/THF, MeCN/THF/H2O and MeOH/...

The synthesis and mesomorphic properties of new series of bent-shaped liquid crystals are presented. The properties of the materials were tuned by the character of the lateral substituent in position 4 of the central aromatic ring and length of terminal alkyl chains. Further modification of physical properties was achieved by the introduction of an...

The long-standing discussion of the absolute configuration of erythro-mefloquine is revisited, showcasing the strength of a combination of experimental and calculated vibrational circular dichroism spectroscopy. The resulting assignment of one of the most important antimalarials is subsequently confirmed by electronic circular dichroism spectroscop...

All-organic paramagnetic liquid crystals offer the advantage of a long-range order of liquid crystalline phases and the magnetic properties of the individual molecules. In such systems, the magnetic properties can be modified by phase transition or the application of external fields. This manuscript reports on paramagnetic all-organic bent-core liq...

We present the enantioseparation of new designer drugs from the cathinone family on structurally different chiral ion-exchange type stationary phases. A novel strong cation-exchange type chiral stationary phase was synthesized and its performance compared with previously reported ion-exchange type chiral stationary phases. The influence of structur...

A new series of azo-containing bent-core liquid crystals derived from 3-hydroxybenzoic acid has been synthesized. Their mesomorphic properties have been characterized by polarizing optical microscopy, differential scanning calorimetry, small-angle x-ray diffraction and electro-optic studies. Almost all the compounds form an enantiotropic modulated...