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Towards complex coupled molecular motions, the remote handedness inversion of a helicene moiety was achieved by a rotary molecular motor. The use of a specifically engineered dynamic helicene stator in a novel overcrowded‐alkene second‐generation molecular motor based on a fluorinated dibenzofluorene fragment allows for an unprecedented control over helicity inversion. This is achieved by the mechanical coupling of the rotation of the rotor to the helicene inversion of the stator half via a remote chirality transmission process. Thus, the unidirectional rotary motion generated upon irradiation is used to invert the dynamic stereochemistry of a helicene, leading to a 6‐step cycle with eight intermediates. In this cycle, both alternation between P and M configurations of the helicene stator and dynamic thermal interconversion (paddling motion) can be achieved. In‐depth computational and spectroscopic studies were performed to support the associated mechanism. The control over coupled motion and dynamic helicity offers prospects for the development of complex responsive systems. [ABSTRACT FROM AUTHOR]

This study investigated the applicability of fluorescent chromophores for exciton‐coupled circular dichroism (ECCD) exploiting fluorescence‐detected circular dichroism (FDCD). FDCD had been previously reported useful in allowing the sensitive detection of ECCD in favorable conditions. However, fluorescence detection may prevent applications of the combined method especially when solutions are polarized in emission. Even without polarization of emission, FDCD deviates from circular dichroism (CD) in some cases when the fluorophore of interest interacts with nonfluorescent chromophore. Herein, it was confirmed that employing 6‐methoxy‐2‐naphthoate always yielded interpretable exciton‐coupled FDCD spectra even when coupling with nonfluorescent p‐substituted benzoates. The 6‐methoxy‐2‐naphthoate chromophore (6‐MN) is prescribed in special cases when only a small amount of sample is available for determining the absolute stereochemistry by the CD exciton chirality method observed by FDCD. [ABSTRACT FROM AUTHOR]

The interface between chirality and crystallization and mechanisms by which chirality propagates from crystal structure to overall shapes of crystals are a key topic in crystallography and stereochemistry. Recently, nanocrystals attracted attention as useful model systems for this kind of studies. Specifically, tellurium nanocrystals have been used to address questions on relations between chirality of the crystal structure and that of the overall shape. Previous studies of this system did not offer a comprehensive shape diagram and did not survey all the factors that determine whether shapes that form are chiral or not. In the current report, the distribution of chiral and achiral shapes in this system as a function of different physical and chemical parameters is determined experimentally. It is shown that there is a common logic for formation of chiral shapes, that is, growth at conditions that favor the growth of more reactive nuclei. The experiments also reveal more morphologies than previously encountered, suggesting that a systematic change of conditions in nanocrystal growth is key for identifying morphologies that exist only in a narrow range of conditions. [ABSTRACT FROM AUTHOR]

Human 15‐lipoxygenase‐1 (15‐LOX‐1) is a key enzyme that possesses an important role in (neuro)inflammatory diseases. The pocket of the enzyme plays the role of a chiral catalyst, and therefore chirality could be an important component for the design of effective enzyme inhibitors. To advance our knowledge on this concept, we developed a library of the identified chiral 15‐LOX‐1 inhibitors and applied cheminformatic tools. Our analysis highlighted specific structural elements, which we integrated them in small molecules, and employed them as "smart" tools to effectively navigate the chemical space of previously unexplored regions. To this purpose, we utilized the marine derived natural product phosphoeleganin (PE) among with a small library of synthetic fragment derivatives, including a certain degree of stereochemical diversity. Enzyme inhibition/kinetic and molecular modelling studies has been performed in order to characterize structurally novel PE‐based inhibitors, which proved to present a different type of inhibition with low micromolar potency, according to their structural features. We demonstrate that different warheads work as anchor, and either guide specific stereochemistry, or causing a time‐depended inhibition. Finally, we prove that the positioning of the chiral substituents or/and the favorable stereochemistry can be crucial, as it can lead from active to completely inactive compounds. [ABSTRACT FROM AUTHOR]

Chirality is traditionally a problematic subject for undergraduate students at the beginning of learning organic chemistry, yet it is of great importance in life sciences. If the initial introduction of chirality is conducted carelessly, students will face ambiguity through the rest of the course and education every time they come across chirality-related subjects. Although there are numerous methods for overcoming the problems of visualization of chiral molecules in 3D space, the connection of chirality with molecular changes like vibrations and conformations is usually not explained thoroughly. In this work, chirality is introduced on dynamic (real) systems, because students from the start should perceive molecules in their natural state of constant motion and change. Apart from the proposition of the lecture concept, exercises are also included, that employ free and readily available software. [ABSTRACT FROM AUTHOR]

The coexistence of two fragments, a chiral isosteviol moiety and an achiral pyridinoyl-hydrazone moiety, in the molecules of pyridinoyl-hydrazone derivatives of isosteviol results in the realization of two distinct supramolecular motifs in their crystals, namely, a true homochiral motif and a pseudosymmetric homochiral motif. [ABSTRACT FROM AUTHOR]

With this report, the space group of [ Z n (N a l) (D A C H) 2 ] C l is corrected ( N a l : nalidixic acid mono-anion; D A C H : diaminocyclohexane) from its wrong description in the literature. In the correct, non-centrosymmetric space group P 1 , the crystal structure is well ordered and the stereochemistry is correct. Crystallographic tools to recognize the correct symmetry are described. This work encourages experienced and inexperienced scientists to remain critical about the output of automatic, black-box crystallographic software. [ABSTRACT FROM AUTHOR]

The transmission of chiral information between the molecular, meso and microscopic scales is a facet of biology that remains challenging to understand mechanistically and to mimic with artificial systems. Here we demonstrate that the dynamic change in the expression of the chirality of a rotaxane can be transduced into a change in pitch of a soft matter system. Shuttling the position of the macrocycle from far‐away‐from to close‐to a point‐chiral center on the rotaxane axle changes the expression of the chiral information that is transmitted across length scales; from nanometer scale constitutional chirality that affects the conformation of the macrocycle, to the centimeter scale chirality of the liquid crystal phase, significantly changing the pitch length of the chiral nematic structure. [ABSTRACT FROM AUTHOR]

This paper explores and revisits in detail the formation and characterization of sugar-based aminonitriles, whose ultimate origin can be traced to the interaction of biomolecules with cyanide. Although the synthesis and spectroscopic data of 2-amino-aldononitriles were reported long ago, there are both contradictory and confusing results among the published data. We have now addressed this concern through an exhaustive structural elucidation of acylated 2-amino- and 2-alkyl(aryl)amino-2-deoxyaldonitriles using mass spectrometry and FT-IR, FT–Raman, and NMR spectroscopies. Several structures could be unambiguously determined through single-crystal X-ray diffraction, which allowed us to correct other misassignments. Moreover, this study unveils how steric and electronic effects influence the acylation outcome of the amino, (alkyl, aryl)amino, or acetamido group at C-2. The chirality at the latter, which was assigned tentatively through optical rotation correlation, and hence the preferential threo stereochemistry generated during the cyanohydrin synthesis of 2-amino-2-deoxy aldononitriles have now been established with confidence. [ABSTRACT FROM AUTHOR]

Manipulating plasmonic chirality has shown promising applications in nanophotonics, stereochemistry, chirality sensing, and biomedicine. However, to reconfigure plasmonic chirality, the strategy of constructing chiral plasmonic systems with a tunable morphology is cumbersome and complicated to apply for integrated devices. Here, we present a simple and effective method that can also manipulate chirality and control chiral light–matter interactions only via strong coupling between chiral plasmonic nanoparticles and excitons. This paper presents a chiral plexcitonic system consisting of L-shaped nanorod dimers and achiral molecule excitons. The circular dichroism (CD) spectra in our strong-coupling system can be calculated by finite element method simulations. We found that the formation of the chiral plexcitons can significantly modulate the CD spectra, including the appearance of new hybridized peaks, double Rabi splitting, and bisignate anti-crossing behaviors. This phenomenon can be explained by our extended coupled-mode theory. Moreover, we explored the applications of this method in enantiomer ratio sensing by using the properties of the CD spectra. We found a strong linear dependence of the CD spectra on the enantiomer ratio. Our work provides a facile and efficient method to modulate the chirality of nanosystems, deepens our understanding of chiral plexcitons in nanosystems, and facilitates the development of chiral devices and chiral sensing. [ABSTRACT FROM AUTHOR]

The discovery and synthetic applications of novel organoselenium compounds and their reactions proceeded rapidly during the past fifty years and such processes are now carried out routinely in many laboratories. At the same time, the growing demand for new enantioselective processes provided new challenges. The convergence of selenium chemistry and asymmetric synthesis led to key developments in the 1970s, although the majority of early work was based on stoichiometric processes. More recently, greater emphasis has been placed on greener catalytic variations, along with the discovery of novel reactions and a deeper understanding of their mechanisms. The present review covers the literature in this field from 2010 to early 2023 and encompasses asymmetric reactions mediated by chiral selenium‐based reagents, auxiliaries, and especially, catalysts. Protocols based on achiral selenium compounds in conjunction with other species of chiral catalysts, as well as reactions that are controlled by chiral substrates, are also included. [ABSTRACT FROM AUTHOR]

The year 1874 is considered to be the birth of stereochemistry when the third dimension in describing and discussing structures in chemistry was first introduced. Stereochemistry and structural chemistry are closely related though they are not each other's synonyms. Structural chemistry implies greater emphasis on metrical aspects and stereochemistry on shape, symmetry, and chirality. We review some of the nodal points in the early development of stereochemistry. [ABSTRACT FROM AUTHOR]

A series of isostructural supramolecular cages with a rhombic dodecahedron shape have been assembled with distinct metal‐coordination lability (M8Pd6‐MOC‐16, M=Ru2+, Fe2+, Ni2+, Zn2+). The chirality transfer between metal centers generally imposes homochirality on individual cages to enable solvent‐dependent spontaneous resolution of Δ8/Λ8−M8Pd6 enantiomers; however, their distinguishable stereochemical dynamics manifests differential chiral phenomena governed by the cage stability following the order Ru8Pd6>Ni8Pd6>Fe8Pd6>Zn8Pd6. The highly labile Zn centers endow the Zn8Pd6 cage with conformational flexibility and deformation, enabling intrigue chiral‐Δ8/Λ8−Zn8Pd6 to meso‐Δ4Λ4−Zn8Pd6 transition induced by anions. The cage stabilization effect differs from inert Ru2+, metastable Fe2+/Ni2+, and labile Zn2+, resulting in different chiral‐guest induction. Strikingly, solvent‐mediated host–guest interactions have been revealed for Δ8/Λ8−(Ru/Ni/Fe)8Pd6 cages to discriminate the chiral recognition of the guests with opposite chirality. These results demonstrate a versatile procedure to control the stereochemistry of metal‐organic cages based on the dynamic metal centers, thus providing guidance to maneuver cage chirality at a supramolecular level by virtue of the solvent, anion, and guest to benefit practical applications. [ABSTRACT FROM AUTHOR]

We report structural studies of a chiral tridentate ligand which forms helical cubanes with cobalt(II) and manganese(II). A quadruple helicate with (P)‐chirality is obtained using a (S)‐ligand with cobalt(II) but the ligand binds manganese(II) in one of two possible orientations and either (P)‐ or (M)‐quadruple helicates may be observed for a given ligand enantiomer. The helicates may be linked into extended structures by p‐nitrobenzoate capping ligands which show stacking interactions with neighbouring complexes. With cobalt(II) we find an extended helical structure with (M)‐chirality linking helicates which themselves have (P)‐chirality. With manganese(II) we observe a remarkable structure with extended (M)‐helices coexisting with extended (P)‐helices. [ABSTRACT FROM AUTHOR]

We study the energy of a ferromagnetic/antiferromagnetic frustrated spin system where the spin takes values on two disjoint circles of the 2-dimensional unit sphere. This analysis will be carried out first on a one-dimensional lattice and then on a two-dimensional lattice. The energy consists of the sum of a term that depends on nearest and next-to-nearest interactions and a penalizing term related to the spins' magnetic anisotropy transitions. We analyze the asymptotic behaviour of the energy, that is when the system is close to the helimagnet/ferromagnet transition point as the number of particles diverges. In the one-dimensional setting we compute the -limit of scalings of the energy at first and second order. As a result, it is shown how much energy the system spends for any magnetic anistropy transition and chirality transition. In the two-dimensional setting, by computing the -limit of a scaling of the energy, we study the geometric rigidity of chirality transitions. [ABSTRACT FROM AUTHOR]

The absolute stereochemistry of the α-amino and α-hydroxyphosphonates is determined using a chiroptical sensor. The induced helicity of the host–guest complex is correlated to the chirality of the guest molecule via a simple binding model. The relative size of the substituents dictates the predominant helical population, leading to an easy circular dichroic readout. [ABSTRACT FROM AUTHOR]

The existence of an object, non-superimposable on its mirror image, constitutes the phenomenon of chirality. This phenomenon is often treated as a curiosity without broader practical consequences. This paper aims to show the significant implications of chirality for chemistry and biology. Chirality is inherent to all living organisms and is essential for their functioning. For instance, biomolecules are composed of chiral building blocks (amino acids, monosaccharides), which are chiral and occur predominantly with one sense of handedness (homochirality of life). The explanation of the evolution of the homochirality of life is therefore one of the important questions connected with the origin of life. The paper also shows why asymmetry with respect to mirror reflection is a general attribute of our world. Historical milestones in the scientific reflection on chirality are also presented, starting with the French crystallographers of the late 18th century, through the work of Pasteur, the fundamentals of organic stereochemistry postulated by van 't Hoff and Le Bel, the elucidation of a structure of monosaccharides by Fischer, and ending with the discovery of the absolute configuration of a molecule and the confirmation of parity violation of weak interaction. [ABSTRACT FROM AUTHOR]

The article discusses the concept of chirality in chemistry, emphasizing its importance and defining it as an absolute property without gradations. It explores the idea of quantifying chirality, with researchers attempting to measure or amplify it, despite chirality being a binary property. The authors caution against using terms like "amplification of chirality" and suggest using more precise language, such as "amplification of optical activity." The article concludes by acknowledging that mistakes and oversights are common in research, urging forgiveness for minor errors in understanding chirality. [Extracted from the article]

The high structural similarity, especially in transmembrane regions, of dopamine, norepinephrine, and serotonin transporters, as well as the lack of all crystal structures of human isoforms, make the specific targeting of individual transporters rather challenging. Ligand design itself is also rather limited, as many chemists, fully aware of the synthetic and analytical challenges, tend to modify lead compounds in a way that reduces the number of chiral centers and hence limits the potential chemical space of synthetic ligands. We have previously shown that increasing molecular complexity by introducing additional chiral centers ultimately leads to more selective and potent dopamine reuptake inhibitors. Herein, we significantly extend our structure-activity relationship of dopamine transporter-selective ligands and further demonstrate how stereoisomers of defined absolute configuration may fine-tune and direct the activity towards distinct targets. From the pool of active compounds, using the examples of stereoisomers 7h and 8h, we further showcase how in vitro activity significantly differs in in vivo drug efficacy experiments, calling for proper validation of individual stereoisomers in animal studies. Furthermore, by generating a large library of compounds with defined absolute configurations, we lay the groundwork for computational chemists to further optimize and rationally design specific monoamine transporter reuptake inhibitors. [ABSTRACT FROM AUTHOR]

The determination of molecular stereochemistry and absolute configuration is an important part of modern chemistry, pharmacology, and biology. Electronic circular dichroism (ECD) spectroscopy is a widely used tool for chirality assignment, especially with porphyrin macrocycles employed as reporter chromophores. However, the mechanisms of induced ECD in porphyrin complexes are yet to be comprehensively rationalized. In this work, the ECD spectra of a sterically hindered hexa‐cationic porphyrin with two camphorsulfonic acids in dichloromethane and chloroform were experimentally measured and computationally analyzed. The influence of geometric factors such as the position of chiral guest molecules, distortion of the porphyrin macrocycle, and orientation of aromatic and non‐aromatic peripheral substituents on the ECD spectra was theoretically studied. Various potential pitfalls, such as a lack of significant conformations and accidental agreement of experimental and simulated spectra, are considered and discussed. [ABSTRACT FROM AUTHOR]

N-thiophthalimido-arylphenothiazines 2 and triarylamines 3 can be converted to dithiabridged triarylamine hetero[4]helicenes 1 using catalytic amounts of chalcogen substituted Lewis Bases and hexafluoro isopropanol as hydrogen bond donor. The procedure occurs under mild reaction conditions and gives good yields avoiding the use of excesses of Lewis Acids as previously reported. A preliminary study about the possibility to control the M and P absolute stereochemistry of helicenes 1 using enantiopure sulfur containing LBs from the natural chiral pool is also reported. [ABSTRACT FROM AUTHOR]

The chiroptical response occurring in the chiral metamaterials (MMs) has crucial and extensive applications for stereochemistry, polarization optics, and spintronics. Yet, such intrinsically chiral metamaterials are restricted to a complicated subwavelength chiral profile, causing pronounced fabrication challenges, particularly at the near‐infrared (N‐IR) spectral regime. Instead, extrinsic chirality can also be observed in the nonchiral MMs under an oblique incidence, indicating that the chiroptical response can be achieved with simple structures. The development of photon‐spin selective integrated devices needs an actively reversible tuning of chirality in MMs. Herein, a reversible switching of the extrinsic chirality at the N‐IR region is demonstrated by integrating a nonvolatile chalcogenide semiconductor, Ge2Sb2Te5, into the nonchiral MMs design. It provides an ultrafast and reconfigurable tuning of transmittance circular dichroism (TCD) between amorphous and crystalline states under a stimulus of a nanosecond pulsed laser at a wavelength of 532 nm. Meanwhile, it also effectively manipulates the TCD by titling both rotation and incident angles while fixing geometrical parameters. Utilizing ellipsometry and analytical inversion, it can obtain not only linear but circular birefringence‐dichroism pairs from a single general ellipsometry measurement, which gives a comprehensive description of the polarization characteristics of the non‐chiral MMs, having an advantage over the typical circular dichroism measurements. [ABSTRACT FROM AUTHOR]

Optical properties of the self-organized gratings in thin photosensitive waveguide AgCl films on a glass substrate, doped by Ag nanoparticles, in the case of simultaneous excitation of TE0 and TE1 modes are investigated. These gratings are a result of interference of the incident linear polarized He-Ne laser beam with the excited TEn-modes of the AgCl layer. The interference field patterns the re-distribution of the nanoparticles. Each excited mode generates its own grating. The self-organized gratings associated with the TE0 mode appear earlier than that of the TE1 mode. There is a competition between TE0-gratings and TE1-gratings for absorbing the nanoparticles, because their available amount is limited in the interaction area. The competition is due to the positive feedback of the light mechanism. Thus, the TE1-grating removes some Ag nanoparticles from the already generated TE0-grating, which forms some chiral complex building blocks of the gratings. The induced chirality leads to the induction and enhancement of optical activities in the samples. Longer exposure of the samples leads to the variation of induced optical chirality. Generation of the gratings increases anisotropy of the sample, which in turn enhances the chiroptical properties of the Ag/AgCl/Glass system. Changes in absorption spectra, induced dichroism, and induced optical gyrotropy of the samples are measured. Diffraction patterns of the exposed samples confirm the coexistence of TE0- and TE1-associated gratings and their competition. AFM images support the above-mentioned process. It is observed that longer exposure and perfect formation of the induced gratings accompany with the reduction of chiroptical property, due to the destruction of chiral complex silver nanoclusters. [ABSTRACT FROM AUTHOR]

Inspired by the signal transduction function of organophosphates in biological systems, bioactive organophosphates were utilized for the first time as chiral nodes to dictate the stereoselective assembly of hydrogen‐bonded anionic cages. Phosphonomycin (antibiotics), tenofovir (antivirals), adenosine monophosphate (natural product, AMP) and clindamycin phosphate (antibiotics) were assembled with an achiral bis‐monourea ligand, thereby leading to the stereoselective formation of quadruple or triple helicates. The extent of the stereoselectivity could be enhanced by either lowering the temperature or adding stronger‐binding cations as templates. With the chiral anionic cages as the host, some enantioselectivity was achieved when binding chiral quaternary ammonium cations. [ABSTRACT FROM AUTHOR]

Certain biological 'receptors' are known to generate disease conditions in the animal/human body. Small molecules, determined by the nature of their groups and shape in three dimensions, fit into the cavities of these receptors and deactivate them, thereby acting as 'drugs'. Several factors, such as pharmacokinetics, pharmacodynamics, metabolism, toxicology and clinical trials, play a crucial role in evaluating any drug. Drugs may be chiral, achiral or racemic in nature. These may be obtained either by extraction from a natural source or by semi-synthetic or synthetic methods. [ABSTRACT FROM AUTHOR]

This study reports the formation of low‐molecular‐weight gelators based on carboxylic acids derived from chiral cyclicβ‐amino acids. The effect of their stereochemistry on the gelation of organic solvents was investigated, and their assemblies with the intermolecular interactions in the xerogels were proposed via infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and crystallographic details of the related model compounds. The effect of the alkyl chain length on the gelators was studied, and they were applied to the chiral recognition of amines. Only one diastereomeric salt with amines afforded gels, whereas the others resulted in precipitates. Chiral recognition was also achieved in the gel state, and the appearance of the as‐prepared gel changed upon the addition of each amine enantiomer, thus enabling the visual detection of their chirality. [ABSTRACT FROM AUTHOR]

Kurt Mislow (1923–2017) and his family were refugees from Nazi Germany. He studied at Tulane University and at Caltech and spent most of his career at Princeton University as Hugh Stott Taylor Professor of Chemistry (from 1988, Emeritus). He excelled in his research and his pedagogy of stereochemistry, introduced the term "chirality" into the chemical textbook literature, and delineated some of the theoretical underpinning of modern stereochemistry. He showed that shape, form, and symmetry play a central role in organic chemistry. He authored an introductory text on stereochemistry that has served generations. His pupils and those who learned from him through his publications carry on his legacy. [ABSTRACT FROM AUTHOR]

We report herein the first systematic crystal structural investigation of azaproline incorporated in homo‐ and heterochiral diprolyl peptides. The X‐ray crystallography data of peptides 1–5 illustrates that stereodynamic nitrogen in azaproline adopted the stereochemistry of neighbouring proline residue without depending on its position in the peptide sequence. Natural bond orbital analysis of crystal structures indicates OazPro−C′Pro of peptides 4 and 5 participating in n→π* interaction with stabilization energy about 1.21–1.33 kcal/mol. Density functional theory calculations suggested that the endo‐proline ring puckering favoured over exo‐conformation by 6.72–7.64 kcal/mol. NBO and DFT data reveals that the n→π* interactions and proline ring puckering stabilize azaproline chirality with the neighbouring proline stereochemistry. The CD, solvent titration, variable‐temperature and 2D NMR experimental results further supported the crystal structures conformation. [ABSTRACT FROM AUTHOR]

• Surface stereochemistry and chirality. • A mini review of our current understanding of the surface chemistry of 1,4-dicarboxylic acids on metal surfaces. • An overview of important aspects of chiral surface chemistry. Dicarboxylic acids, including tartaric acid, have played a crucial role alongside amino acids in the study of chiral recognition on metal surfaces. Over the past two decades, significant insights into surface stereochemistry have emerged, particularly on Cu(110). This review examines various phenomena observed during the interaction of 1,4-dicarboxylic acids with the Cu(110) surface. We explore diverse aspects such as chiral surface reconstructions, intermolecular chiral recognition, stereoselective autocatalytic decomposition, and chiral symmetry breaking through doping. [Display omitted] [ABSTRACT FROM AUTHOR]

Chiral trifluoromethyl alcohol groups were introduced at the hindered ortho positions of 9,10‐diphenylanthracenes to investigate their effects on the physical properties and reactivity towards oxidative dearomatization. In such compact structures, the position in different quadrants and the preferred orientation of the −CH(OH)CF3 groups were determined by the relative and absolute configurations of each stereoisomer, respectively. As a consequence, the stereochemistry governs the organization of the H‐bonded molecules in single crystals (homochiral dimers vs ribbon), whereas in chlorinated solvents, they all behave as discrete compounds. Concerning their reactivity, the stereospecific dearomative oxidation of these molecules leads to 9,10‐bis‐spiro‐isobenzofuran‐anthracenes, when using organic single‐electron transfer oxidants. The chiroptical properties of the alcohols and the corresponding dearomatized products were compared and showed an important modulation of the intensity. [ABSTRACT FROM AUTHOR]

Stabilization of chiral propeller conformations in triaryl compounds is challenging due to generally low racemization barriers. Nonetheless, it was recently found that chiral conformational preferences can be induced to triaryl boranes by incorporating point‐chiral alkylether chains to the aryl blades and subsequently locking the structure with ammonia. A four‐point interaction, meaning that the cooperative effects of Lewis‐adduct formation and three hydrogen bonds, was proposed as stabilizing mechanism. Herein, it was shown that three such strong interactions suffice to introduce a preferential propeller handedness. Although DFT calculations predict no noteworthy preferences for either P‐ or M‐chiral propellers for some of the investigated triarylborane–amine adducts that were prepared with chiral primary amines, vibrational circular dichroism (VCD) spectroscopic characterizations revealed that there is indeed a measurable excess of one propeller handedness. Furthermore, the steric demand of the amine was found to play a key role in the induction process and especially in preventing blade rotations. [ABSTRACT FROM AUTHOR]

Conjugating the porphyrin ring with an amino acid via amide linkage represents a straightforward way for conferring both amphiphilicity and chirality to the macrocycle. Proline residue is a good choice in this context since its conformational rigidity allows for porphyrin assembling where molecular chirality is efficiently transferred and amplified using properly honed aqueous environments. Herein, we describe the evolution of the studies carried out by our group to achieve chiral systems from some porphyrin-proline derivatives, both in solution and in the solid state. The discussion focuses on some fundamental aspects reflecting on the final molecular architectures obtained, which are related to the nature of the appended group (stereochemistry and charge), the presence of a metal ion coordinated to the porphyrin core and the bulk solvent properties. Indeed, fine-tuning the mentioned parameters enables the achievement of stereospecific structures with distinctive chiroptical and morphological features. Solid films based on these chiral systems were also obtained and their recognition abilities in gaseous and liquid phase are here described. [ABSTRACT FROM AUTHOR]

The paper considers supramolecular organization of molecules in the crystals of two luminophores, derivatives of the family of fluorinated boron-dipyrromethene complexes (BODIPY) differing by the substituent in the meso-position of the indacene core. It is shown that a stable dimeric motif is transferred from the racemic crystal to the chiral one to form two supramolecular diastereomers in the latter case. Quantum chemical DFT calculations along with the topological analysis of the calculated electron density reveal that C–H⋯F interactions play a leading role in the formation of these dimers; a presence of weaker intradimer interactions C–H⋯π, C–H⋯O, and π⋯π is demonstrated. [ABSTRACT FROM AUTHOR]

Incommensurate double-wall carbon nanotubes give rise to unique stereochemistry originating from twisted stacks of hexagon arrays. However, atomic-level studies on such unique systems have rarely been performed, even though syntheses of molecular segments of carbon nanotubes have been extensively explored. The design of cylindrical molecules with chirality, particularly, in pairs provides synthetic challenges, because relationships between diameters specified with chiral indices and structures of arylene panels have not been investigated in a systematic manner. Here we show that a molecular version of incommensurate double-wall carbon nanotubes can be designed through the development of an atlas for the top-down design of cylindrical molecules. A large-bore cylindrical molecule with a diameter of 1.77 nm was synthesized using a readily available pigment and encapsulated a small-bore cylindrical molecule with a diameter of 1.04 nm. The large- and small-bore molecules possessed helicity in atomic arrangements, and their coaxial assembly proceeded in nonstereoselective manner to give both heterohelical and homohelical combinations. Incommensurate double-wall carbon nanotubes give rise to unique stereochemistry originating from twisted stacks of hexagon arrays, but atomic-level studies of molecular analogues are hindered by the challenges in designing and synthesizing pairs of chiral cylindrical molecules. Here, a molecular version of incommensurate double-wall carbon nanotubes is designed by development of a roadmap of synthetically accessible chiral indices. [ABSTRACT FROM AUTHOR]

Chirality is one of the key factors affecting the medicinal efficacy of compounds. In addition to central chirality, sterically hindered chiral axes commonly appear in drugs and the resulting chirality is known as atropisomerism. With developments in medicinal chemistry, atropisomerism has attracted increasing attention. This review discusses the classification, biological activity, pharmacokinetics, toxicity and side effects of atropisomers, and can serve as a reference in the research and development of potential chiral drugs. [ABSTRACT FROM AUTHOR]

We present the first investigation of the influence of chirality on the thermal and electric properties in a biologically important homomeric dipeptide that exhibits a hexagonal columnar liquid crystal mesophase. The peptide employed has two chiral centres, and thus the two possible enantiopures are the (R,R) and (S,S) forms having opposite chirality. The measurements reported the span of the binary phase space between these two enantiopures. Any point in the binary diagram is identified by the enantiomeric excess Xee (the excess content of the R,R enantiopure over its S,S counterpart). We observe that the magnitude of Xee plays a pivotal role in governing the properties as evidenced by X-ray diffraction (XRD), electric polarization (Ps), dielectric relaxation spectroscopy (DRS) measurements, and the isotropic-columnar transition temperature. For example, XRD shows that while other features pointing to a hexagonal columnar phase remain the same, additional short-range ordering, indicating correlated discs within the column, is present for the enantiopures (Xee = ±1) but not for the racemate (Xee = 0). Similarly, an electric-field driven switching whose profile suggests the phase structure to be antiferroelectric is seen over the entire binary space, but the magnitude is dependent on Xee; interestingly the polarization direction is axial, i.e., along the column axis. DRS studies display two dielectric modes over a limited temperature range and one mode (mode 2) connected with the antiferroelectric nature of the columnar structure covering the entire mesophase. The relaxation frequency and the thermal behaviour of mode 2 are strongly influenced by Xee. The most attractive effect of chirality is its influence on the polar order, a measure of which is the magnitude of the axial polarization. This result can be taken to be a direct evidence of the manifestation of molecular recognition and the delicate interplay between chiral perturbations and the magnitude of the polar order, a feature attractive from the viewpoint of devices based on, e.g., remnant polarization—a currently hot topic. To add further dimension to the work, the DRS measurements are also extended to elevated pressures. [ABSTRACT FROM AUTHOR]

Molecular self‐assembly of the minimal diphenylalanine (Phe‐Phe) peptide building block shows unique morphological organizations and potential utility in biochemistry and biomaterials applications. Furthermore, the molecular engineering of nucleoside‐conjugated Phe‐Phe scaffolds allows the formation of diverse architectures with tunable biophysical properties. While the self‐assembly of homochiral l‐dipeptides is well characterized, stereochemistry is known to determine the conformation, which also governs self‐assembly through molecular packing effects. Here, the effect of stereochemistry and hydrophobicity on Phe‐Phe nucleoside conjugates using all four diastereomers [(l)Phe‐(l)Phe, (d)Phe‐(dPhe, (l)Phe‐(d)Phe, and (d)Phe‐(l)Phe] of Phe‐Phe conjugates is systematically studied. The homochiral peptides form well‐defined nanorods while the heterochiral dipeptides do not form any regular structures. Since heterocyclic nucleobases can self‐assemble through hydrogen‐bonded complementary base‐pairing, the self‐assembly of chiral nucleoside‐conjugated Phe‐Phe peptides is examined. All conjugated Phe‐Phe peptides form seamless spherical particles. The completely or partially deprotected peptides do not assemble to any defined nanostructures suggesting that self‐assembly is governed by the precise hydrophobic/hydrophilic balance in the assembling units. Contact angle measurements of the diastereomeric peptides reveal a subtle difference in stereochemistry‐dependent molecular hydrophobicity. Taken together, it is revealed that the combination of chirality together with hydrophobic/hydrophilic balance within the peptides dictates the self‐assembly of Phe‐Phe dipeptide nucleoside conjugates. [ABSTRACT FROM AUTHOR]

This communication is devoted to the theoretical and synthetic aspects of the stereochemistry of organophosphorus compounds. The nature of the chirality generation in the prebiotic period, the mechanisms of asymmetric induction, and double stereodifferentiation are discussed. The use of these methods for the preparation of chiral phosphorus analogs of natural compounds (phosphono-isonorstatin, phosphono-GABOB, phosphacarnitine, bis-phosphonates, and others) is described. Some data concerning of λ5-phosphanediones as metaphosphate anion analogues were also reported. [ABSTRACT FROM AUTHOR]

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Peripheral substitution of a π‐extended porphyrin with bulky groups produces a curved chromophore with four helical stereogenic units. The curvature and stereochemistry of such porphyrins can be controlled by varying the substituents, coordinated metal ions, and apical ligands. In particular, when the achiral saddle‐shaped free bases are treated with large metal ions, i.e., CdII or HgII, the resulting complexes convert to chiral propeller‐like configurations. X‐ray diffraction analyses show that apical coordination of a water molecule is sufficient to induce a notable bowl‐like distortion of the cadmium complex, which however retains its chiral structure. For phenyl‐ and tolyl‐substituted derivatives, the conversion is thermodynamically controlled, whereas complexes bearing bulky 4‐(tert‐butyl)phenyl groups transform into their chiral forms upon heating. In the latter case, the chiral Hg porphyrin was converted into the corresponding free base and other metal complexes without any loss of configurational purity, ultimately providing access to stable, enantiopure porphyrin propellers. [ABSTRACT FROM AUTHOR]

Inhibition of human DNA repair enzyme tyrosyl-DNA phosphodiesterase 1 (Tdp1) by different chiral lipophilic nucleoside derivatives was studied. New Tdp1 inhibitors were found in the series of the studied compounds with IC50 = 2.7–6.7 μM. It was shown that D-lipophilic nucleoside derivatives manifested higher inhibition activity than their L-analogs, and configuration of the carbohydrate moiety can influence the mechanism of Tdp1 inhibition. [ABSTRACT FROM AUTHOR]