Chiral Teropyrenes: Synthesis, Structure, and Spectroscopic Studies.

We present the inaugural synthesis of a chiral teropyrene achieved through a four-fold alkyne benzannulation catalyzed by InCl3, resulting in good yields. The product underwent thorough characterization using FT-Raman and FT-IR spectroscopies, demonstrating a close agreement with calculated spectra. X-ray crystallographic analysis unveiled a notable twist in the molecule's backbone, with an end-to-end twist angle of 51°, consistent with computational predictions. Experimentally determined enantiomeric inversion barriers revealed a significant energy barrier of 23 kcal/mol, facilitating the isolation of enantiomers for analysis by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopies. These findings mark significant strides in the synthesis and characterization of chiral teropyrenes, offering insights into their structural and spectroscopic properties.

Theoretically Predicted and Experimentally Detected Chirality of Dibenzocyclooctynes and Their Triazole Adducts with Azides.

Dibenzocyclooctynes have emerged as promising scaffolds for bioorthogonal ligation. An important structural aspect that has not been addressed so far relates to their chirality. Herein, we explore, by theoretical and experimental methods, this structural aspect that has been neglected so far. First, computational analysis is conducted, and the results are used as a guide for the experimental investigation. Next, an array of different experiments (high-performance liquid chromatography (HPLC) on chiral columns, chiroptical spectroscopy, and X-ray diffraction) for structure elucidation is scrutinized in concert. Finally, this work demonstrates the chirality and the stereodynamic behavior of dibenzocyclooctynes and their triazole derivatives with simple azides and also uncovers their conformational behavior.

Inherently chiral helicene-substituted thioalkyl porphyrazine complexes: synthesis and electronic and chiroptical properties.

The chiral Ni(II) and Pd(II) complexes of [6]helicene thioethyl porphyrazine have been synthesized and their spectroscopic, electrochemical, and chiroptical properties have been investigated by experimental and computational analyses. In these compounds, the tetrapyrrole macrocycle is ß-substituted with an inherently chiral extended aromatic moiety potentially suitable to establish attractive π-π interactions with nanocarbons and endowed with helical chirality, both features providing interesting properties for optoelectronic applications. Experimental and density functional theory computational analyses highlight the presence of HOMO-LUMO charge-transfer transitions between the helicene moiety and the porphyrazine macrocycle. These compounds behave as mono-substituted push-pull systems without any typical electron-withdrawing or electron-donating groups and thus appear promising for optoelectronics. The enantiomers of the Ni(II) complex have been separated by chiral HPLC and their absolute configuration has been established by density functional theory computational analysis of electronic circular dichroism spectra. The magnetic circular dichroism spectrum of this complex has also been recorded providing better insight into its electronic structure.

Chromatographic separation of the interconverting enantiomers of imidazo- and triazole-fused benzodiazepines.

The toolbox of medicinal chemists includes the 1,4-benzodiazepine scaffold as a "privileged scaffold" in drug discovery. Several biologically active small molecules containing a 1,4-benzodiazepine scaffold have been approved by the FDA for the treatment of various diseases, with most of them being used for their psychotropic effects. The therapeutic potential of 1,4-benzodiazepines has stimulated the interest of synthetic chemists in developing new synthetic strategies to a range of substituted analogues for biological evaluation. A structural variation of the classical benzodiazepine skeleton is observed e.g. in alprazolam, midazolam, and related benzodiazepines, which contain a 1,2,4-triazole or an imidazole ring fused to the benzodiazepine core. Irrespective of the presence of the fused heterocyclic ring, the seven-membered diazepine ring is far from planar, and its shape resembles a twist chair. Then, the unsymmetrical substitution pattern around the seven membered cycle renders these molecules chiral, as they lack any reflection-type symmetry element. However, chirality of this molecules is labile at room temperature, becausea simple ring flipping process converts one enantiomer into the other, and 1,4-benzodiazepines exist as a mixture of rapidly interconverting conformational enantiomers in solution at or near room temperature. Physical separation of the interconverting enantiomers of diazepam and of other related 1,4-benzodiazepin-2-ones can be accomplished by low temperature HPLC on chiral stationary phases (CSPs). If the HPLC column is cooled down to temperatures where the interconversion rate is sufficiently low, compared to the chromatographic separation rate, distinct separated peaks can be observed, provided the CSP is sufficiently enantioselctive. The apparent rate constants for the on-column enantiomerization and the corresponding free energy activation barriers were obtained by simulation of exchange-deformed HPLC profiles using a computer program based on the stochastic model. Here we report on the dynamic HPLC investigations carried out on a set of fused imidazo and triazolo-benzodiazepines (alprazolam, midazolam, triazolam and estazolam) The experimental dynamic chromatograms and the corresponding interconversion barriers reported in this paper show that the third fused heterocyclic ring increase the energy barrier by 2 kcal/mol.

Molecular Recognition of the HPLC Whelk-O1 Selector towards the Conformational Enantiomers of Nevirapine and Oxcarbazepine.

The presence of stereogenic elements is a common feature in pharmaceutical compounds, and affording optically pure stereoisomers is a frequent issue in drug design. In this context, the study of the chiral molecular recognition mechanism fundamentally supports the understanding and optimization of chromatographic separations with chiral stationary phases. We investigated, with molecular docking, the interactions between the chiral HPLC selector Whelk-O1 and the stereoisomers of two bioactive compounds, the antiviral Nevirapine and the anticonvulsant Oxcarbazepine, both characterized by two stereolabile conformational enantiomers. The presence of fast-exchange enantiomers and the rate of the interconversion process were studied using low temperature enantioselective HPLC and VT-NMR with Whelk-O1 applied as chiral solvating agent. The values of the energetic barriers of interconversion indicate, for the single enantiomers of both compounds, half-lives sufficiently long enough to allow their separation only at critically sub-ambient temperatures. The chiral selector Whelk-O1 performed as a strongly selective discriminating agent both when applied as a chiral stationary phase (CSP) in HPLC and as CSA in NMR spectroscopy.

Synthesis, Resolution, Configurational Stability, and Properties of Cationic Functionalized [5]Helicenes.

A straightforward approach to the synthesis of two different series of cationic [5]helicenes has been achieved including, in dioxa series, the possibility to introduce aromatic functional groups at the periphery of the helical structure. While photophysical study highlights that the introduction of aryl substituents at position 23 of the helical moieties has a negligible impact on the optical properties, styryl substituents allow a welcoming extension of the conjugation pathways. Finally, a red shift of the optical properties was evidenced upon introduction of nitrogen atoms in the helicene scaffold, leading to particularly good fluorescence efficiencies in the red domain for a helicenic dye. Detailed information on racemization kinetics was collected for the most stable species upon direct high-performance liquid chromatography (HPLC) resolution or, when configurational lability was too high, through VT-HPLC analysis on the chiral stationary phase (ΔG‡ values ranging from 85.0 to 137.1 kJ·mol-1 and above).

The Pictet-Spengler Reaction Updates Its Habits.

The Pictet-Spengler reaction (P-S) is one of the most direct, efficient, and variable synthetic method for the construction of privileged pharmacophores such as tetrahydro-isoquinolines (THIQs), tetrahydro-ß-carbolines (THBCs), and polyheterocyclic frameworks. In the lustro (five-year period) following its centenary birthday, the P-S reaction did not exit the stage but it came up again on limelight with new features. This review focuses on the interesting results achieved in this period (2011-2015), analyzing the versatility of this reaction. Classic P-S was reported in the total synthesis of complex alkaloids, in combination with chiral catalysts as well as for the generation of libraries of compounds in medicinal chemistry. The P-S has been used also in tandem reactions, with the sequences including ring closing metathesis, isomerization, Michael addition, and Gold- or Brønsted acid-catalyzed N-acyliminium cyclization. Moreover, the combination of P-S reaction with Ugi multicomponent reaction has been exploited for the construction of highly complex polycyclic architectures in few steps and high yields. The P-S reaction has also been successfully employed in solid-phase synthesis, affording products with different structures, including peptidomimetics, synthetic heterocycles, and natural compounds. Finally, the enzymatic version of P-S has been reported for biosynthesis, biotransformations, and bioconjugations.

Synthesis of pyrano[2,3-f]chromen-2-ones vs. pyrano[3,2-g]chromen-2-ones through site controlled gold-catalyzed annulations.

Regioselective access to 10-substituted-2H,8H-pyrano[2,3-f]chromen-2-ones through the gold-catalyzed intramolecular hydroarylation of readily available 7-(prop-2-yn-1-yloxy)-2H-chromen-2-one derivatives at their C-8 congested position was investigated by tuning the electronic and steric properties of the ligand on the gold complex. On the other hand, the combination of the JohnPhosAu(MeCN)SbF6 catalyzed intramolecular hydroarylation of 8-iodo-7-(prop-2-yn-1-yloxy)-2H-chromen-2-one derivatives followed by selective palladium/formate C-I reduction allows for the exclusive formation of 2H,8H-pyrano[3,2-g]chromen-2-one regioisomers. The development of these two protocols provides versatile synthetic tools required for exploring the biological activities of these new pyranocoumarin derivatives.

Four-Fold Alkyne Benzannulation: Synthesis, Properties, and Structure of Pyreno[a]pyrene-Based Helicene Hybrids.

The synthesis of pyreno[a]pyrene-based helicene hybrids was achieved in good yield via a four-fold alkyne benzannulation reaction that was promoted by Brønsted acid. The molecules are configurationally locked, allowing the enantiomers to be separated using chiral HPLC so that their photophysical and chiroptical properties, including circular dichroism and circularly polarized luminescence, could be studied.

Determination of the absolute configuration of conformationally flexible molecules by simulation of chiro-optical spectra: a case study.

The assignment of the absolute configuration (AC) of two conformational flexible organic molecules by means of TD-DFT simulation of the electronic circular dichroism (ECD) spectra is presented. The factors leading to a reliable assignment were evaluated in the various steps of the process. The effects of different functionals and basis sets in the geometry optimization step is very limited in terms of the resulting optimized geometries, whereas the inclusion of the solvent in the calculations has a much larger effect on the correct evaluation of the conformational ratio. B3LYP and M06-2x were found to be the most accurate functionals for geometry optimization. CAM-B3LYP and ωB97X-D provided the best results in the TD-DFT simulations.

Comparação da função motora em solo e imersão de pacientes com distrofia muscular de Duchenne em acompanhamento fisioterapêutico - follow-up de 2 anos / Comparison of motor function in patients with Duchenne muscular dystrophy in physical therapy in and out of water: 2-year follow-up

O tratamento para pacientes com Distrofia Muscular de Duchenne (DMD) é multidisciplinar. Faz-se necessário entender os efeitos das atividades executadas em solo e imersão para permitir o desenvolvimento de protocolos de intervenção. Objetivo: Comparar a função motora em solo e imersão, no período de 2 anos, em crianças com DMD em acompanhamento fisioterapêutico. Método: Estudo retrospectivo com 23 pacientes diagnosticados DMD, de 8 a 24 anos, assistidos pela Associação Brasileira de Distrofia Muscular (ABDIM). Foram coletados dados da avaliação em imersão (adaptação ao meio líquido, bipedestação, sedestação, rotação transversal, longitudinal, nado e marcha) e em solo (Escalas Egan Klassification e Vignos), no período de dois anos. Resultados: Na análise das avaliações entre os semestres, no período de 2 anos, houve diferença no desempenho das atividades em imersão (p < 0,001) e não foi observada diferença na Escala Egan Klassification (p < 0,003) e na Escala Vignos (p < 0,012). Conclusão: Devido aos princípios físicos da água os pacientes apresentaram manutenção e melhora do escore da avaliação da função motora em imersão. Em contrapartida, foi demonstrada piora dos escores das Escalas Egan Klassification e Vignos que representam a função motora em solo

The treatment for patients with Duchenne Muscular Dystrophy (DMD) is multidisciplinary. It is necessary to understand the effects of activities performed on dry ground as well as water-immersed to allow the development of intervention protocols. Objective: To compare the motor function of children with DMD in physiotherapy carried out on the ground and immersed over a 2-year period. Method: A retrospective study, assisted by the Brazilian Association of Muscular Dystrophy (ABDIM), of 23 patients diagnosed with DMD, 8-24 years of age. We collected assessment data both water-immersed (adaptation to the water, bipedalism, sitting position, cross and longitudinal rotation, swimming, and running) and on the ground (Egan Klassifikation Scale and Vignos Scale) over a 2-year period. Results: Analyzing the ratings between semesters during the 2-year period, there were differences in the performance of water-immersed activities (p < 0.001) and there was no difference on the Egan Klassifikation Scale (p < 0.003) or the Vignos Scale (p < 0.012). Conclusion: Due to the physical properties of the water, patients either improved or maintained their scores for motor function in water immersion. However, their scores for the Egan Klassifikation and the Vignos scales, which represent motor function on the ground, diminished