Organocatalytic hydrogen bond donor/Lewis base (HBD/LB) synthesis and chiroptical properties of thiabridged [5]helicenes.

Thiabridged [5]helicenes are obtained from thioaryl--phthalimido benzo[]phenothiazines using a hydrogen bond donor/Lewis base organocatalytic approach. Resolution of [5]helicenes using either (1)-(-)-camphanic acid as a chiral auxiliary or CSP-HPLC is reported. Thiabridged [5]helicenes show an exceptional configurational stability with racemization energy barriers higher than 40 kcal mol.

When the diagnosis is written in the DNA: a case of erythropoietic protoporphyria in a patient with a chromosome-18 deletion.

In this case study, we describe a 21-year-old man with erythropoietic protoporphyria who sought medical attention in April 2022 for diffuse edema and erythema of the hands. These symptoms had been present since childhood and usually occurred soon after sun exposure. The patient's medical history showed that chromosome 18's long arm had partially deleted.

CPL of Mellein and Related Natural Compounds: Analysis of the ESIPT Phenomenon.

(R)-(-)-Mellein, (3R,4R)-4-hydroxymellein and (3R,4S)-4-hydroxymellein obtained from fungi, i. e. from Diplodia globulosa, were investigated as a class of natural products presenting ESIPT (excited state intramolecular proton transfer) phenomenon, through fluorescence and CPL (circularly polarized luminescence).

Mid-IR and CH stretching vibrational circular dichroism spectroscopy to distinguish various sources of chirality: The case of quinophaneoxazoline based ruthenium(II) complexes.

Five diastereomers of ruthenium(II) complexes based on quinolinophaneoxazoline ligands were investigated by vibrational circular dichroism (VCD) in the mid-IR and CH stretching regions. Diastereomers differ in three sources of chirality: the planar chirality of the quinolinophane moiety, the central chirality of an asymmetric carbon atom of the oxazoline ring, and the chirality of the ruthenium atom. VCD, allied to DFT calculations, has been found to be effective in disentangling the various forms of chirality.

Neurodegeneration: can metabolites from help?

The number of patients affected by neurodegenerative diseases is increasing worldwide, and no effective treatments have been developed yet. Although precision medicine could represent a powerful tool, it remains a challenge due to the high variability among patients. To identify molecules acting with innovative mechanisms of action, we performed a computational investigation using SAFAN technology, focusing specifically on HuD.

Scaling-up VPT2: A feasible route to include anharmonic correction on large molecules.

Vibrational analysis plays a crucial role in the investigation of molecular systems. Though methodologies like second-order vibrational perturbation theory (VPT2) have paved the way to more accurate simulations, the computational cost remains a difficult barrier to overcome when the molecular size increases. Building upon recent advances in the identification of resonances, we propose an approach making anharmonic simulations possible for large-size systems, typically unreachable by standard means.

Sigma receptor and aquaporin modulators: chiral resolution, configurational assignment, and preliminary biological profile of RC752 enantiomers.

The key role of chiral small molecules in drug discovery programs has been deeply investigated throughout last decades. In this context, our previous studies highlighted the influence of the absolute configuration of different stereocenters on the pharmacokinetic, pharmacodynamic and functional properties of promising Sigma receptor (SR) modulators. Thus, starting from the racemic SR ligand RC752, we report herein the isolation of the enantiomers via enantioselective separation with both HPLC and SFC.

Pushing measurements and interpretation of VCD spectra in the IR, NIR and visible ranges to the detectability and computational complexity limits.

(R)-Limonene VCD and IR absorption spectra for neat liquid samples are considered from 900 to 16,000 cm, using mostly data by Nafie et al. up to 10,000 cm and from previous investigations of the Brescia group. New VCD data are recorded in the merely overtone and combination region between 1800 and 2400 cm and for the Δn= 6 overtone CH-stretching region above 15,000 cm.

Circularly polarized luminescence of natural products lycorine and narciclasine: role of excited-state intramolecular proton-transfer and test of pH sensitivity.

Circularly polarized luminescence (CPL) is increasingly gaining interest not only for its applicative potentialities but also for providing an understanding of the excited state properties of chiral molecules. However, applications of CPL are mainly in the field of materials science: special organic molecules and polymers, metal (lanthanide) complexes, and organic dyes are actively and intensely studied. So far natural compounds have not been investigated much.

Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives.

In this work we review research activities on a few of the most relevant structural aspects of bilirubin (BR) and biliverdin (BV). Special attention is paid to the exocyclic C=C bonds being in mostly rather than configurations, and to the overall conformation being essentially different for BR and BV due to the presence or absence of the double C=C bond at C-10. In both cases, racemic mixtures of each compound of either or configuration are present in achiral solutions; however, imbalance between the two configurations may be easily achieved.

Anharmonic Aspects in Vibrational Circular Dichroism Spectra from 900 to 9000 cm for Methyloxirane and Methylthiirane.

Vibrational circular dichroism (VCD) spectra and the corresponding IR spectra of the chiral isomers of methyloxirane and of methylthiirane have been reinvestigated, both experimentally and theoretically, with particular attention to accounting for anharmonic corrections, as calculated by the GVPT2 approach. De novo recorded VCD spectra in the near IR (NIR) range regarding CH-stretching overtone transitions, together with the corresponding NIR absorption spectra, were also considered and accounted for, both with the GVPT2 and with the local mode approaches. Comparison of the two methods has permitted us to better describe the nature of active "anharmonic" modes in the two molecules and the role of mechanical and electrical anharmonicity in determining the intensities of VCD and IR/NIR data.

Spectroscopic investigation on 1,2-substituted ferrocenes with only planar chirality: How chiroptical data are related to absolute configuration and to substituents.

Single enantiomers of three 1,2-substituted ferrocene derivatives, i.e. 1-methoxymethyl-2-hydroxymethylferrocene (1), 1-formyl-2-hydroxymethylferrocene (2) and 1-iodo-2-hydroxymethylferrocene (3), sharing the common hydroxymethyl substituent and the presence of planar chirality only, were investigated for their spectroscopic (IR and UV) and chiroptical (VCD and ECD) properties.

Helicity control of a perfluorinated carbon chain within a chiral supramolecular cage monitored by VCD.

Confinement within supramolecular systems is the leading technology to finely tune guest functional properties. In this communication we report the synthesis of a chiral supramolecular cage able to bias the helicity of a perfluorinated carbon chain hosted within the cage. We monitor the phenomenon of chiral induction by Vibrational Circular Dichroism (VCD) experiments complemented by DFT calculations over the possible conformers.

The Assignment of the Absolute Configuration of Non-Cyclic Sesquiterpenes by Vibrational and Electronic Circular Dichroism: The Example of Metabolites.

9-Hydroxynerolidol, 9-oxonerolidol, and chiliadenol B are three farnesane-type sesquiterpenoids isolated from that have shown an interesting activity against human pathogens as Gram+ and Gram- bacteria resistant to antibiotics. However, the absolute configuration (AC) of these interesting sesquiterpenes has not been assigned so far. Vibrational and electronic circular dichroism spectra have been recorded and correlations are pointed out for the three compounds.

MCD and MCPL Characterization of Luminescent Si(IV) and P(V) Tritolylcorroles: The Role of Coordination Number.

Two triarylcorrole complexes, (hydroxy)[5,10,15-tritolylcorrolato]silicon- and (dihydroxy)[5,10,15-tritolylcorrolato]phosphorous- , have been investigated by magnetic circular dichroism (MCD) and magnetic circularly polarized luminescence (MCPL). The spectroscopic investigations have been combined with explicit calculation of MCD response through time-dependent density functional theory (TD-DFT) formalism. This has allowed us to better define the role of molecular orbitals in the transitions associated with the Soret and Q bands.

Biliverdin chiral derivatives as chiroptical switches for pH and metal cation sensing.

A series of six optically active derivatives of the bile pigment biliverdin, namely (β,β')-dimethylmesobiliverdin-XIIIα, cyclic esters of linear diols [HO(CH)OH] where = 1-6, have been investigated by vibrational circular dichroism (VCD) and density functional theory (DFT) calculations. The results were correlated with the length () of the diester belt, the verdin helicity and an ⇄ conformational equilibrium - as previously shown by electronic circular dichroism (ECD). Furthermore, ECD spectra have been found to be quite sensitive to solvent nature and pH.

Implementation of the NHI (Normalized Hot Spot Indices) Algorithm on Infrared ASTER Data: Results and Future Perspectives.

The Normalized Hotspot Indices (NHI) tool is a Google Earth Engine (GEE)-App developed to investigate and map worldwide volcanic thermal anomalies in daylight conditions, using shortwave infrared (SWIR) and near infrared (NIR) data from the Multispectral Instrument (MSI) and the Operational Land Imager (OLI), respectively, onboard the Sentinel 2 and Landsat 8 satellites. The NHI tool offers the possibility of ingesting data from other sensors. In this direction, we tested the NHI algorithm for the first time on Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data.

Testing the vibrational exciton and the local mode models on the instructive cases of dicarvone, dipinocarvone, and dimenthol vibrational circular dichroism spectra.

The vibrational circular dichroism (VCD) spectra of dicarvone (1), dipinocarvone (2), and dimenthol (3) have been recorded in the range 900-3200 cm , encompassing the mid-infrared (mid-IR), the CO stretching, and the CH-stretching regions. For compound 3 also, the fundamental and the first overtone OH stretching regions have been investigated by IR/NIR absorption and VCD. Density functional theory (DFT) calculations allow one to interpret the IR and VCD spectra and to confirm the configuration/conformational studies previously conducted by X-ray diffraction.

Characterization of tetrakis(thiadiazole)porphyrazine metal complexes by magnetic circular dichroism and magnetic circularly polarized luminescence.

The magnetic circular dichroism (MCD) spectra of metal complexes of tetrakis(thiadiazole)porphyrazines ([TTDPzM] with M = 2H , Zn , Mg (H O), and Cd ) have been recorded in dimethyl formamide solution. Together with the UV-Vis spectra, the MCD spectra provide useful information about the structure and electronic properties of the complexes. The experimental UV-Vis and MCD spectra compare pretty well with DFT calculations of two sorts, based either on the sum-over-states (SOS) approach or on the complex polarization propagator approach.

Amplification of the chiroptical response of UV-transparent amines and alcohols by N-phthalimide derivatization enabling absolute configuration determination through ECD computational analysis.

The stereoselective transformation of chiral UV-transparent amines and alcohols to phthalimides has proved to be a simple and efficient method to enhance the chiroptical response of these substrates allowing their reliable absolute configuration determination by computational analysis of ECD spectra. Such a transformation also leads to a significant reduction in the molecular conformational flexibility thus simplifying the conformational analysis required by the computational treatment. The method described herein thus allows the absolute configuration assignment to these challenging substrates to be much easier and reliable.

Toward Fully Unsupervised Anharmonic Computations Complementing Experiment for Robust and Reliable Assignment and Interpretation of IR and VCD Spectra from Mid-IR to NIR: The Case of 2,3-Butanediol and -1,2-Cyclohexanediol.

The infrared (IR) and vibrational circular dichroism (VCD) spectra of 2,3-butanediol and -1,2-cyclohexanediol from 900 to 7500 cm (including mid-IR, fundamental CH and OH stretchings, and near-infrared regions) have been investigated by a combined experimental and computational strategy. The computational approach is rooted in density functional theory (DFT) computations of harmonic and leading anharmonic mechanical, electrical, and magnetic contributions, followed by a generalized second-order perturbative (GVPT2) evaluation of frequencies and intensities for all the above regions without introducing any ad hoc scaling factor. After proper characterization of large-amplitude motions, all resonances plaguing frequencies and intensities are taken into proper account.

Unbiased Determination of Absolute Configurations by vis-à-vis Comparison of Experimental and Simulated Spectra: The Challenging Case of Diplopyrone.

A new experimental-computational strategy for the determination of the absolute configuration (AC) of complex chiral molecules is proposed by combining diverse experimental spectroscopies with quantum-mechanical simulations well beyond the current computational practice. Key features are the conformer search and relative stability evaluation performed by a new stochastic two-level tool followed by a vis-à-vis comparison of experimental and computed spectra without any ad hoc adjustment. The entire computational procedure is embedded in the user-friendly VMS software, and its reliability is granted by the inclusion of mechanic/electric/magnetic anharmonicity as well as ro-vibrational and vibronic couplings by means of generalized perturbation theory in conjunction with double-hybrid functionals combined with empirical dispersion contributions and suitable basis sets.

Optically active Ag(i): o-OPE helicates using a single homochiral sulfoxide as chiral inducer.

In this work we describe the ability of a simple enantiopure sulfoxide group to promote folding of oligo ortho-phenylene ethynylenes (o-OPEs) with one helical sense. A family of foldamers with up to seven triple bonds was synthesized and fully characterized. Moreover, changes in structure and chiroptical properties caused by Ag(i) coordination have been studied by NMR, UV, VCD and ECD measurements.

Assignment Through Chiroptical Methods of The Absolute Configuration of Fungal Dihydropyranpyran-4-5-Diones Phytotoxins, Potential Herbicides for Buffelgrass () Biocontrol.

Radicinin and cochliotoxin ( and ) two phytotoxic pyranpyran-4,5-diones were isolated together with their close metabolites 3--radicinin, radicinol, and its 3-epimer (-), from the culture filtrates of , a fungus proposed as mycoherbcide for biocontrol of buffelgrass, a very noxious and dangerous weed. The absolute configuration of cochliotoxin was determined by chiroptical Optical Rotatory Dispersion (ORD), Electronic Circular Dichroism (ECD), and Vibrational Circular Dichroism (VCD)) and computational methods. The same methods were used to confirm that of radicinin, radicinol and their 3-epimers, previously determined with chemical, spectroscopic and ECD methods.