Tailor-Made Amino Acids and Fluorinated Motifs as Prominent Traits in Modern Pharmaceuticals

Fluorinated Protein-Ligand Complexes: A Computational Perspective

Fluorine is an element renowned for its unique properties. Its powerful capability to modulate molecular properties makes it an attractive substituent for protein binding ligands; however, the rational design of fluorination can be challenging with effects on interactions and binding energies being difficult to predict. In this Perspective, we highlight how computational methods help us to understand the role of fluorine in protein-ligand binding with a focus on molecular simulation. We underline the importance of an accurate force field, present fluoride channels as a showcase for biomolecular interactions with fluorine, and discuss fluorine specific interactions like the ability to form hydrogen bonds and interactions with aryl groups. We put special emphasis on the disruption of water networks and entropic effects.

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

An efficient multicomponent reaction of newly designed β-trifluoromethyl β-diazo esters, acetonitrile, and carboxylic acids via an interrupted esterification process under copper-catalyzed conditions has been developed, which affords various unsymmetrical β-trifluoromethyl N,N-diacyl-β-amino esters in good to excellent yields. The reaction features mild conditions, a wide scope of β-amino esters and carboxylic acids, and also applicability to large-scale synthesis, thus providing an efficient way for the synthesis of β-trifluoromethyl β-diacylamino esters. Furthermore, this reaction represents the first example of a Mumm rearrangement of β-trifluoromethyl β-diazo esters.

Latest developments in coumarin-based anticancer agents: mechanism of action and structure-activity relationship studies

Many researchers around the world are working on the development of novel anticancer drugs with different mechanisms of action. In this case, coumarin is a highly promising pharmacophore for the development of novel anticancer drugs. Besides, the hybridization of this moiety with other anticancer pharmacophores has emerged as a potent breakthrough in the treatment of cancer to decrease its side effects and increase its efficiency. This review aims to provide a comprehensive overview of the recent development of coumarin derivatives and their application as novel anticancer drugs. Herein, we highlight and describe the largest number of research works reported in this field from 2015 to August 2023, along with their mechanisms of action and structure-activity relationship studies, making this review different from the other review articles published on this topic to date.

Hydroxytrifluoroethylation and Trifluoroacetylation Reactions via SET Processes

Hydroxytrifluoroethyl and trifluoroacetyl groups are of utmost importance in biologically active compounds, but methods to tether these motifs to organic architectures have been limited. Typically, the preparation of these compounds relied on the use of strong bases or multistep routes. The renaissance of radical chemistry in photocatalytic, transition metal mediated, and hydrogen atom transfer (HAT) processes have allowed the installation of these medicinally relevant fluorinated motifs. This review provides an overview of the methods available for the direct synthesis of hydroxytrifluoroethyl- and trifluoroacetyl-derived compounds governed by single-electron transfer processes.

Trifluoromethylthiolation of Tryptophan and Tyrosine Derivatives: A Tool for Enhancing the Local Hydrophobicity of Peptides

The incorporation of fluorinated groups into peptides significantly affects their biophysical properties. We report herein the synthesis of Fmoc-protected trifluoromethylthiolated tyrosine (CF3S-Tyr) and tryptophan (CF3S-Trp) analogues on a gram scale (77-93% yield) and demonstrate their use as highly hydrophobic fluorinated building blocks for peptide chemistry. The developed methodology was successfully applied to the late-stage regioselective trifluoromethylthiolation of Trp residues in short peptides (66-80% yield) and the synthesis of various CF3S-analogues of biologically active monoamines. To prove the concept, Fmoc-(CF3S)Tyr and -Trp were incorporated into the endomorphin-1 chain (EM-1) and into model tripeptides by solid-phase peptide synthesis. A remarkable enhancement of the local hydrophobicity of the trifluoromethylthiolated peptides was quantified by the chromatographic hydrophobicity index determination method, demonstrating the high potential of CF3S-containing amino acids for the rational design of bioactive peptides.

Tinker, Tailor, Soldier, Spy: The Diverse Roles That Fluorine Can Play within Amino Acid Side Chains

Side chain-fluorinated amino acids are useful tools in medicinal chemistry and protein science. In this review, we outline some general strategies for incorporating fluorine atom(s) into amino acid side chains and for elaborating such building blocks into more complex fluorinated peptides and proteins. We then describe the diverse benefits that fluorine can offer when located within amino acid side chains, including enabling 19F NMR and 18F PET imaging applications, enhancing pharmacokinetic properties, controlling molecular conformation, and optimizing target-binding.

Chemistry and Pharmacology of Fluorinated Drugs Approved by the FDA (2016-2022)

Fluorine is characterized by high electronegativity and small atomic size, which provide this molecule with the unique property of augmenting the potency, selectivity, metabolic stability, and pharmacokinetics of drugs. Fluorine (F) substitution has been extensively explored in drug research as a means of improving biological activity and enhancing chemical or metabolic stability. Selective F substitution onto a therapeutic or diagnostic drug candidate can enhance several pharmacokinetic and physicochemical properties such as metabolic stability and membrane permeation. The increased binding ability of fluorinated drug target proteins has also been reported in some cases. An emerging line of research on F substitution has been addressed by using 18F as a radiolabel tracer atom in the extremely sensitive methodology of positron emission tomography (PET) imaging. This review aims to report on the fluorinated drugs approved by the US Food and Drug Administration (FDA) from 2016 to 2022. It cites selected examples from a variety of therapeutic and diagnostic drugs. FDA-approved drugs in this period have a variety of heterocyclic cores, including pyrrole, pyrazole, imidazole, triazole, pyridine, pyridone, pyridazine, pyrazine, pyrimidine, triazine, purine, indole, benzimidazole, isoquinoline, and quinoline appended with either F-18 or F-19. Some fluorinated oligonucleotides were also authorized by the FDA between 2019 and 2022.

Deoxygenation of ClSO2CF2COOMe with Triphenylphosphine for the Metal-Free Direct Electrophilic Difluoroalkylthiolation of Various Heterocycles

A direct electrophilic difluoroalkylthiolation reaction of indole derivatives and other electron-rich heterocycles using methyl 2,2-difluoro-2-(chlorsulfonyl)acetate (ClSO₂CF₂COOMe) derived from Chen's reagent (FSO₂CF₂COOMe) is described. The ester group in the product can be further utilized in subsequent versatile transformations. The reactions provide good yields of the corresponding difluoroalkylthiolation products and exhibit high functional group compatibility. It is expected to serve as an alternative and practical protocol for difluoroalkylthiolation of various heterocycles.

New Approved Drugs Appearing in the Pharmaceutical Market in 2022 Featuring Fragments of Tailor-Made Amino Acids and Fluorine

The strategic fluorination of oxidatively vulnerable sites in bioactive compounds is a relatively recent, widely used approach allowing us to modulate the stability, bio-absorption, and overall efficiency of pharmaceutical drugs. On the other hand, natural and tailor-made amino acids are traditionally used as basic scaffolds for the development of bioactive molecules. The main goal of this review article is to emphasize these general trends featured in recently approved pharmaceutical drugs.

Catalytic Asymmetric α-Functionalization of α-Branched Aldehydes

Aldehydes constitute a main class of organic compounds widely applied in synthesis. As such, catalyst-controlled enantioselective α-functionalization of aldehydes has attracted great interest over the years. In this context, α-branched aldehydes are especially challenging substrates because of reactivity and selectivity issues. Firstly, the transient trisubstituted enamines and enolates resulting upon treatment with an aminocatalyst or a base, respectively, would exhibit attenuated reactivity; secondly, mixtures of E- and Z-configured enamines/enolates may be formed; and third, effective face-discrimination on such trisubstituted sp2 carbon intermediates by the incoming electrophilic reagent is not trivial. Despite these issues, in the last 15 years, several catalytic approaches for the α-functionalization of prostereogenic α-branched aldehydes that proceed in useful yields and diastereo- and enantioselectivity have been uncovered. Developments include both organocatalytic and metal-catalyzed approaches as well as dual catalysis strategies for forging new carbon–carbon and carbon–heteroatom (C-O, N, S, F, Cl, Br, …) bond formation at Cα of the starting aldehyde. In this review, some key early contributions to the field are presented, but focus is on the most recent methods, mainly covering the literature from year 2014 onward.

Diastereoselective Synthesis of Highly Functionalized Proline Derivatives

An efficient way to access highly functionalized proline derivatives was developed based on a Cu(I)-catalyzed reaction between CF₃-substituted allenynes and tosylazide, which involved a cascade of [3 + 2]-cycloaddition/ketenimine and a rearrangement/Alder-ene cyclization to afford the new proline framework with a high diastereoselectivity.

Asymmetric Alkylation of Cyclic Ketones with Dehydroalanine via H-Bond-Directing Enamine Catalysis: Straightforward Access to Enantiopure Unnatural α-Amino Acids

The growing importance of structurally diverse and functionalized enantiomerically pure unnatural amino acids in the design of drugs, including peptides, has stimulated the development of new synthetic methods. This study reports the challenging direct asymmetric alkylation of cyclic ketones with dehydroalanine derivatives via a conjugate addition reaction for the synthesis of enantiopure ketone-based α-unnatural amino acids. The key to success was the design of a bifunctional primary amine-thiourea catalyst that combines H-bond-directing activation and enamine catalysis. The simultaneous dual activation of the two relatively unreactive partners, confirmed by mass spectrometry studies, results in high reactivity while securing high levels of stereocontrol. A broad substrate scope is accompanied by versatile downstream chemical modifications. The mild reaction conditions and consistently excellent enantioselectivities (>95 % ee in most cases) render this protocol highly practical for the rapid construction of valuable noncanonical enantiopure α-amino-acid building blocks.

Synthesis of Functionalized Azepines via Cu(I)-Catalyzed Tandem Amination/Cyclization Reaction of Fluorinated Allenynes

An efficient method for the selective preparation of trifluoromethyl-substituted azepin-2-carboxylates and their phosphorous analogues has been developed via Cu(I)-catalyzed tandem amination/cyclization reaction of functionalized allenynes with primary and secondary amines.

The Latest FDA-Approved Pharmaceuticals Containing Fragments of Tailor-Made Amino Acids and Fluorine

Nowadays, the selective introduction of fluorine into bioactive compounds is a mature strategy in the design of drugs allowing to increase efficiency, biological half-life and bio-absorption. On the other hand, amino acids (AAs) represent one of the most ubiquitious classes of naturally occurring organic compounds, which are found in over 40% of newly marked small-molecule pharmaceutical drugs and medical formulations. The primary goal of this work is to underscore two major trends in the design of modern pharmaceuticals. The first is dealing with the unique structural characteristics provided by the structure of amino acids featuring an abundance of functionality and the presence of a stereogenic center, all of which bodes well for the successful development of targeted bioactivity. The second is related to fine-tuning the desired activity and pharmacokinetics by selective introduction of fluorine. Historically, both trends were developed separately as innovative and prolific approaches in modern drug design. However, in recent decades, these approaches are clearly converging leading to an ever-increasing number of newly approved pharmaceuticals containing both structural features of amino acids and fluorine.

Fluorinated triazoles as privileged potential candidates in drug development—focusing on their biological and pharmaceutical properties

Fluorinated heterocycles have attracted extensive attention not only in organic synthesis but also in pharmaceutical and medicinal sciences due to their enhanced biological activities than their non-fluorinated counterparts. Triazole is a simple five-membered heterocycle with three nitrogen atoms found in both natural and synthetic molecules that impart a broad spectrum of biological properties including but not limited to anticancer, antiproliferative, inhibitory, antiviral, antibacterial, antifungal, antiallergic, and antioxidant properties. In addition, incorporation of fluorine into triazole and its derivatives has been reported to enhance their pharmacological activity, making them promising drug candidates. This mini-review explores the current developments of backbone-fluorinated triazoles and functionalized fluorinated triazoles with established biological activities and pharmacological properties.

Study of Carbamoyl Fluoride: Synthesis, Properties and Applications

Carbamoyl fluoride is a fluorinated group that, to this date, remains underexplored, probably due to the lack of data concerning its properties. In this paper, a study of carbamoyl fluoride is presented. Stability studies, in particular under physiological conditions, and lipophilicity measurement were performed. A new easy, safe, inexpensive, and metal-free synthesis method is also described. Finally, a potential use in radiochemistry through a ¹⁸ F/¹⁹ F isotopic exchange is demonstrated.

Selectively Fluorinated Citronellol Analogues Support a Hydrogen Bonding Donor Interaction with the Human OR1A1 Olfactory Receptor

C-2 fluorinated and methylated stereoisomers of the fragrance citronellol 1 and its oxalate esters were prepared from (R)-pulegone 11 and explored as agonists of the human olfactory receptor OR1A1 and assayed also against site-specific mutants. There were clear isomer preferences and C-2 difluorination as in 18 led to the most active compound suggesting an important hydrogen bond donor role for citronellol 1. C-2 methylation and the corresponding oxalate ester analogues were less active.

Asymmetric Michael Addition in Synthesis of β-Substituted GABA Derivatives

γ-Aminobutyric acid (GABA) represents one of the most prolific structural units widely used in the design of modern pharmaceuticals. For example, β-substituted GABA derivatives are found in numerous neurological drugs, such as baclofen, phenibut, tolibut, pregabalin, phenylpiracetam, brivaracetam, and rolipram, to mention just a few. In this review, we critically discuss the literature data reported on the preparation of substituted GABA derivatives using the Michael addition reaction as a key synthetic transformation. Special attention is paid to asymmetric methods featuring synthetically useful stereochemical outcomes and operational simplicity.

Tailor-Made Amino Acids in Pharmaceutical Industry: Synthetic Approaches to Aza-Tryptophan Derivatives

Over the recent years there has been a noticeable upsurge of interest in aza-analogs of tryptophan which are isosteric to the latter and found numerous applications in medicinal, bioorganic chemistry, and peptide research. In the present review article, five aza-tryptophan derivatives are profiled, including aza-substitution in the positions 2, on the five-membered ring, as well as in positions 4, 5, 6, and 7 on the six-membered ring. A detailed and comprehensive literature overview of the synthetic methods for the preparation of these aza-tryptophans is presented and general facets of the biological properties and most promising applications are discussed.

Advances in the Development of Trifluoromethoxylation Reagents

This review provides a short summary of the traditional methods for synthesis of CF3-O-containing compounds, followed by a critical overview of known trifluoromethoxylating reagents, focusing on their preparation, synthetic generality and limitations.

Recent Advances on the Halo- and Cyano-Trifluoromethylation of Alkenes and Alkynes

Incorporation of fluorine into organic molecules is a well-established strategy in the design of advanced materials, agrochemicals, and pharmaceuticals. Among numerous modern synthetic approaches, functionalization of unsaturated bonds with simultaneous addition of trifluoromethyl group along with other substituents is currently one of the most attractive methods undergoing wide-ranging development. In this review article, we discuss the most significant contributions made in this area during the last decade (2012−2021). The reactions reviewed in this work include chloro-, bromo-, iodo-, fluoro- and cyano-trifluoromethylation of alkenes and alkynes.

Lossen rearrangement by Rh(III)-catalyzed C-H activation/annulation of aryl hydroxamates with alkynes: access to quinolone-containing amino acid derivatives

A convenient and robust method for the preparation of new CF₃-containing 2-quinolones has been developed via a Rh(III)-catalyzed C-H activation/Lossen rearrangement/annulation cascade of N-pivaloyloxy-arylamides with internal alkynes bearing an α-CF₃-α-amino acid moiety on the triple bond. This work expands the scope of valuable products that are available through C-H activation/annulation reactions of arylamides in organic synthesis.

New pharmaceuticals approved by FDA in 2020: Small-molecule drugs derived from amino acids and related compounds

Amino acids (AAs) play an important role in the modern health industry as key synthetic precursors for pharmaceuticals, biomaterials, biosensors, and drug delivery systems. Currently, over 30% of small-molecule drugs contain residues of tailor-made AAs or derived from them amino-alcohols and di-amines. In this review article, we profile 12 AA-derived new pharmaceuticals approved by the FDA in 2020. These newly introduced drugs include Tazverik (epithelioid sarcoma), Gemtesa (overactive bladder), Zeposia (multiple sclerosis), Byfavo (induction and maintenance of procedural sedation), Cu 64 dotatate, and Gallium 68 PSMA-11 (both PET imaging), Rimegepant (acute migraine), Zepzelca (lung cancer), Remdesivir (COVID-19), Amisulpride (nausea and vomiting), Setmelanotide (obesity), and Lonafarnib (progeria syndrome). For each compound, we describe the spectrum of biological activity, medicinal chemistry discovery, and synthetic preparation.

Biomimetic enantioselective synthesis of β,β-difluoro-α-amino acid derivatives

Although utilization of fluorine compounds has a long history, synthesis of chiral fluorinated amino acid derivatives with structural diversity and high stereoselectivity is still very appealing and challenging. Here, we report a biomimetic study of enantioselective [1,3]-proton shift of β,β-difluoro-α-imine amides catalyzed by chiral quinine derivatives. A wide range of corresponding β,β-difluoro-α-amino amides were achieved in good yields with high enantioselectivities. The optically pure β,β-difluoro-α-amino acid derivatives were further obtained, which have high application values in the synthesis of fluoro peptides, fluoro amino alcohols and other valuable fluorine-containing molecules.

Photocatalysis in the Life Science Industry

In the pursuit of new pharmaceuticals and agrochemicals, chemists in the life science industry require access to mild and robust synthetic methodologies to systematically modify chemical structures, explore novel chemical space, and enable efficient synthesis. In this context, photocatalysis has emerged as a powerful technology for the synthesis of complex and often highly functionalized molecules. This Review aims to summarize the published contributions to the field from the life science industry, including research from industrial-academic partnerships. An overview of the synthetic methodologies developed and strategic applications in chemical synthesis, including peptide functionalization, isotope labeling, and both DNA-encoded and traditional library synthesis, is provided, along with a summary of the state-of-the-art in photoreactor technology and the effective upscaling of photocatalytic reactions.

Selective Transformation of Norbornadiene into Functionalized Azaheterocycles and β-Amino Esters with Stereo- and Regiocontrol

Novel functionalized azaheterocycles with multiple chiral centers have been accessed from readily available norbornene β-amino acids or β-lactams across a stereocontrolled synthetic route, based on ring-opening metathesis (ROM) of the staring unsaturated bicyclic amino esters, followed by selective cyclization through ring-closing metathesis (RCM). The RCM transformations have been studied under various experimental conditions to assess the scope of conversion, catalyst, yield, and substrate influence. The structure of the starting norbornene β-amino acids predetermined the structure of the new azaheterocycles, and the developed synthetic route took place with the conservation of the configuration of the chiral centers.

Janus All-Cis 2,3,4,5,6-Pentafluorocyclohexyl Building Blocks Applied to Medicinal Chemistry and Bioactives Discovery Chemistry

Monoalkylated derivatives of the unusually polar all‐cis 2,3,4,5,6‐ pentafluorocyclohexyl (Janus face) motif are prepared starting from an aryl hydrogenation of 2,3,4,5,6‐ pentafluorophenylacetate methyl ester 15. The method used Zeng's Rh(CAAC) carbene catalyst 4 in the hydrogenation following the protocol developed by Glorius. The resultant Janus pentafluorocyclohexylacetate methyl ester 16 was converted to the corresponding alcohol 18, aldehyde 13, bromide 29 and azide 14 through functional group manipulations, and some of these building blocks were used in Ugi‐multicomponent and Cu‐catalysed click reactions. NBoc protected pentafluoroarylphenylalanine methyl ester 35 was also subject to an aryl hydrogenation, and then deprotection to generate the Janus face β‐pentafluorocyclohexyl‐alanine amino acid 15, which was incorporated into representative members of an emerging class of candidate antiviral compounds. Log P measurements demonstrate that the all‐cis 2,3,4,5,6‐pentafluorocyclohexyl ring system is more polar than a phenyl ring. In overview the paper introduces new building blocks containing this Janus ring and demonstrates their progression to molecules typically used in bioactives discovery programmes.

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

This work presents an examination of the selective functionalization of norbornadiene through nitrile oxide 1,3-dipolar cycloaddition/ring-opening metathesis (ROM)/cross-metathesis (CM) protocols. Functionalization of commercially available norbornadiene provided novel bicyclic scaffolds with multiple stereogenic centers. The synthesis involved selective cycloadditions, with subsequent ROM of the formed cycloalkene-fused isoxazoline scaffolds and selective CM by chemodifferentiation of the olefin bonds of the resulting alkenylated derivatives. Various experimental conditions were applied for the CM transformations with the goal of exploring substrate and steric effects, catalyst influence and chemodifferentiation of the olefin bonds furnishing the corresponding functionalized, fluorine-containing isoxazoline derivatives.

Comparative study of different chiral ligands for dynamic kinetic resolution of amino acids

Dynamic kinetic resolution (DKR) of unprotected amino acids (AAs), via intermediate formation of Ni(II) complexes, is currently a leading methodology for preparation of natural and tailor-made AAs in enantiomerically pure form. In this work, we conduct a comparative case study of synthetic performance of four different ligands in DKR of six AAs representing aryl-, benzyl-, alkyl-, and long alkyl-type derivatives. The results of this study allow for rational selection of ligand/AA type to develop a practical procedure for preparation of target enantiomerically pure AAs.

Trifluoromethylselenolation and N-acylation of indoles with [Me4N][SeCF3]

An efficient method for oxidative trifluoromethylselenolation/N-acylation of indoles with excess [Me₄N][SeCF₃] in the presence of acyl peroxides and their derivatives is described. The reaction is easy to handle, proceeds smoothly at room temperature under metal-free conditions, and shows advantages such as good functional group tolerance, excellent regioselectivity, and compatibility of a number of substrates, producing 1-acyl and 3-trifluoromethylselanyl substituted indoles in good yields. Acyl peroxides and peroxycarboxylic acid behave as both oxidants and acyl sources in the transformation. This one-pot procedure provides a convenient access to a new class of indole derivatives, representing the first trifluoromethylselanyl bifunctionalization of indoles with the nucleophilic [Me₄N][SeCF₃] reagent.

A general asymmetric synthesis of artificial aliphatic and perfluoroalkylated α-amino acids by Luche's cross-electrophile coupling reaction

Aliphatic artificial α-amino acids (α-AAs) have attracted great interest in biochemistry and pharmacy. In this context, we developed a promising practical protocol for the asymmetric synthesis of these α-AAs through the selective and efficient intermolecular cross-electrophile coupling of Belokon's chiral dehydroalanine Ni(ii) complex with different alkyl and perfluoroalkyl iodides mediated by a dual Zn/Cu system. The reaction afforded diastereomeric complexes with dr up to 21.3 : 1 in 24-95% yields (19 examples). Exemplarily, three enantiomerically pure aliphatic α-AAs were obtained through acidic decomposition of (S,S)-diastereomers of Ni(ii) complexes. Importantly, the chiral auxiliary ligand (S)-BPB ((S)-2-(N-benzylprolyl)aminobenzophenone) was easily recycled by simple filtration after acidic complex decomposition and reused for the synthesis of the initial dehydroalanine Ni(ii) complex.

Recommended Tests for the Self-Disproportionation of Enantiomers (SDE) to Ensure Accurate Reporting of the Stereochemical Outcome of Enantioselective Reactions

The purpose of this review is to highlight the necessity of conducting tests to gauge the magnitude of the self-disproportionation of enantiomers (SDE) phenomenon to ensure the veracity of reported enantiomeric excess (ee) values for scalemic samples obtained from enantioselective reactions, natural products isolation, etc. The SDE always occurs to some degree whenever any scalemic sample is subjected to physicochemical processes concomitant with the fractionation of the sample, thus leading to erroneous reporting of the true ee of the sample if due care is not taken to either preclude the effects of the SDE by measurement of the ee prior to the application of physicochemical processes, suppressing the SDE, or evaluating all obtained fractions of the sample. Or even avoiding fractionation altogether if possible. There is a clear necessity to conduct tests to assess the magnitude of the SDE for the processes applied to samples and the updated and improved recommendations described herein cover chromatography and processes involving gas-phase transformations such as evaporation or sublimation.

Fluorinated Rings: Conformation and Application

The introduction of fluorine atoms into molecules and materials across many fields of academic and industrial research is now commonplace, owing to their unique properties. A particularly interesting feature is the impact of fluorine substitution on the relative orientation of a C-F bond when incorporated into organic molecules. In this Review, we will be discussing the conformational behavior of fluorinated aliphatic carbo- and heterocyclic systems. The conformational preference of each system is associated with various interactions introduced by fluorine substitution such as charge-dipole, dipole-dipole, and hyperconjugative interactions. The contribution of each interaction on the stabilization of the fluorinated alicyclic system, which manifests itself in low conformations, will be discussed in detail. The novelty of this feature will be demonstrated by presenting the most recent applications.

Chemical Aspects of Human and Environmental Overload with Fluorine

Over the last 100-120 years, due to the ever-increasing importance of fluorine-containing compounds in modern technology and daily life, the explosive development of the fluorochemical industry led to an enormous increase of emission of fluoride ions into the biosphere. This made it more and more important to understand the biological activities, metabolism, degradation, and possible environmental hazards of such substances. This comprehensive and critical review focuses on the effects of fluoride ions and organofluorine compounds (mainly pharmaceuticals and agrochemicals) on human health and the environment. To give a better overview, various connected topics are also discussed: reasons and trends of the advance of fluorine-containing pharmaceuticals and agrochemicals, metabolism of fluorinated drugs, withdrawn fluorinated drugs, natural sources of organic and inorganic fluorine compounds in the environment (including the biosphere), sources of fluoride intake, and finally biomarkers of fluoride exposure.