Testosterone, the most important human male sex hormone, plays a key role in multiple important biological processes. Along with its ester derivatives, they are often abused by amateur as well as professional sportsmen and bodybuilders for muscle growth enhancement. Their overuse, however, can lead to serious health problems. In this work, electronic and vibrational circular dichroism (ECD, VCD) and density functional theory (DFT) calculations were used for a detailed analysis of testosterone and testosterone propionate in solutions. Stable conformers were found for both compounds, their spectra were calculated and subsequently compared to the experiment. In the case of testosterone propionate, DFT and VCD combined with a shape fitting algorithm suggested relative abundances of the stable conformers, which should be independently verified. Also, the influence of two different solvents (water and methanol) on the ECD spectra was examined. Chiroptical spectroscopy proved to be a powerful tool for analysing steroid compounds, the biological activity of which has attracted attention for many decades.

Amphetamine derivatives are considered most seized substances worldwide. In this study, solid-state vibrational circular dichroism (VCD) measurements of enantiomerically pure substances were performed for spectroscopic discrimination between (S)- and (R)-enantiomers. First, we have developed a universal experimental approach to obtain reliable and reproducible solid-state VCD spectra. First, the samples were prepared as pellets composed of mixtures of camphor as a model compound and a crystalline matrix powder. In order to obtain the best results without artifacts and with a maximum signal-to-noise ratio, the following experimental conditions were optimized: pellet thickness and diameter and sample rotation speed. The optimized parameters were then used for the analysis of amphetamine and its derivatives (methamphetamine and 3,4-methylendioxymethamphetamine). Our high-quality spectra and results suggest that solid-state VCD spectroscopy represents a cost-effective and easy-to-use method for the analysis of conformation changes and molecular packing in solid-state with potential applications in pharmaceutical and forensic practice.

Mefloquine, a widely used antimalarial agent, has spurred ongoing research into the development of derivatives with enhanced efficacy and reduced side effects. In this investigation, we synthesized two compounds containing N-allyl or N-tert-butylacetamid groups. A chiral liquid chromatography with polysaccharide chiral stationary phase was utilized to separate the enantiomers of both derivatives. We employed spectroscopic chiroptical and non-polarizable methods such as electronic and vibrational circular dichroism, infrared absorption and ultraviolet spectroscopies. Combined with density functional theory calculations, the stable conformers were found in solution and their spectra were subsequently simulated. We elucidated the three-dimensional structure of the enantiomerically pure compounds and assigned the absolute configuration of all prepared derivatives using both experimental and simulated spectra.

An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated.

Recently, the number of structural modifications of synthetic cathinones has been growing making them the second largest group of new psychoactive substances in Europe. Although they are abused because of their various psychoactive effects, some compounds from this group also serve as pharmaceuticals. Since synthetic cathinones are chiral molecules with one chiral center, their biological, toxicological, and pharmacological properties may significantly differ according to their absolute configuration and enantiomeric excess. In this study, we have synthesized two substances bearing a pharmacologically interesting trifluoromethyl group and developed a chiral liquid chromatography method using a polysaccharide chiral stationary phase to separate the corresponding enantiomers of both these drugs. Subsequently, we utilized molecular spectroscopic methods including chiroptical (electronic circular dichroism and vibrational circular dichroism) and non-polarizable (infrared and ultraviolet absorption) spectroscopies. In combination with density functional theory calculations, we have obtained stable conformers of selected enantiomers in solution and their relative abundances, which we used to simulate their spectra. The experimental and calculated data have been used to elucidate the 3D structure of the enantiomerically pure compounds and assign the absolute configuration of all prepared compounds.

Colorectal cancer (CRC) remains a significant threat to human health because of the lack of awareness of physical examination or the limitations of an early diagnostic level. Despite the improving standard of modern medicine, mortality from CRC is still remarkably high and the prognosis remains poor in many cases because of disease detection at advanced clinical stages. Raman spectroscopy yields precise information, not only regarding the secondary structure of proteins but also regarding the discrimination between normal and malignant tissues. We investigated whether this method can be used for the diagnosis of CRC including initial stages. To acquire more detailed structural information, we tested a novel diagnostic approach based on a suitable combination of conventional methods of molecular spectroscopy (Raman and Fourier transform infrared) with advanced, highly structure-sensitive chiroptical techniques as electronic circular dichroism (ECD) and Raman optical activity (ROA) to monitor the CRC pathogenesis relating compositional, structural and conformational changes in blood biomolecules, some of which may be caused by pathological processes occurring during cancer growth, also at the beginning of the disease. Sixty-three blood plasma samples were analyzed using the combination of ECD and ROA supplemented by Raman and Fourier transform infrared (FT-IR) spectroscopies. The obtained spectra were evaluated together by linear discriminant analysis. The accuracy of sample discrimination reached 100% and the subsequent leave-one-out cross-validation resulted in 90% sensitivity and 75% specificity. There were also found the differences between the patients according to the clinical stage. The achieved results suggest a panel of promising biomarkers and indicate that chiroptical methods combined with conventional spectroscopies might be a new minimally invasive powerful tool for producing high-quality data, obtaining an accurate diagnosis of colorectal cancer through a peripheral blood sample, which is also able to determine the extent of this pathology. Further work needs to be carried out for these techniques to be implemented in the clinical setting.

The infrared (IR) and vibrational circular dichroism (VCD) spectra of S-2,2'-dimethyl-biphenyl-6,6'-dicarboxylic acid, S-1, in CDCl(3) solution are concentration-dependent, showing that oligomerization occurs with increasing concentration. DFT calculations support the conclusion that the oligomer formed is the cyclic tetramer (S-1)(4), in which S-1 monomers are linked by hydrogen(H)-bonded (COOH)(2) moieties. Due to the existence of two inequivalent tautomeric conformations of each (COOH)(2) moiety, six inequivalent conformations of (S-1)(4) are possible. B3LYP/6-31G* DFT calculations predict that the conformation "aaab", possessing three equivalent (COOH)(2) conformations, a, and one tautomeric conformation, b, has the lowest free energy. B3LYP/6-31G* IR and VCD spectra vary substantially with conformation. The B3LYP/6-31G* IR and VCD spectra of the C=O stretch modes of "aaab" are in excellent agreement with the experimental spectra, while those of all other conformations exhibit poor agreement, confirming the prediction that the "aaab" conformation is the predominant conformation. Comparison of the calculated IR and VCD spectra of the six conformations to the experimental spectra in the range 1100-1600 cm(-1) further supports this conclusion. The study is the first to use VCD spectroscopy to determine the structure of a supramolecular species.

Solid complexes of D-galacturonic acid (GalA) with cobalt(II), copper(II), nickel(II) and oxovanadium(IV) (1-4) were prepared and characterised. The metal-to-ligand molar ratio was 1:2 for complexes 1-3 and 1:1 for complex 4. The alpha- and beta-anomers of GalA were detected in all the complexes in solid state and in solutions. An addition of small amounts of the paramagnetic complexes to the D2O solution of pure ligand led to NMR line broadening of some 1H and 13C nuclei. This broadening was sensitive to the anomeric state of GalA in the case of complexes 1 and 4. NMR and vibrational spectroscopic data indicate the formation of carboxylate complexes of all the cations, while noncarboxylic oxygens are also involved into the metal bonding in some cases. VCD spectra of complexes 1-4 in D2O and Me2SO-d6 solutions confirm that GalA carboxylic group may participate in the formation of optically active species around the metal cation. Possible ways of GalA coordination by metal cations of this study were proposed and discussed.

Infrared absorption and vibrational circular dichroism (VCD) spectra of four Corey lactone derivatives (diol, benzoate, p-phenylbenzoate, and bisbenzoate) were measured and analyzed on the basis of ab initio computations. The analysis interpreted most of the spectral features as well as the differences among individual compounds. Despite the common rigid lactone residue, conformational behaviors and spectral features of the derivatives were found to be different, because of hydrogen bonding and solvent effects. Recognition of common molecular parts in the spectra of different molecules increases the potential of using VCD for monitoring the purity of intermediates in chiral syntheses. For the derivatives, a conserved spectral component corresponding to the lactone skeleton could be identified on the basis of theoretical analysis but was relatively weak in intensity.

The host/guest complexation between cyclodextrins (CDs) and aromatic compounds was studied by vibrational circular dichroism (VCD) spectroscopy in mid-IR region. Benzoic acid, 4-aminobenzoic acid, and 2,6-naphthalenedicarboxylic acid acting as the guests with aromatic skeleton, cause the significant changes in VCD patterns of CD, which indicate that the secondary hydroxyl groups of the CDs are involved in the host/guest complexation. In addition, the intensities and dissymmetry factors (ΔA/A) of the VCD bands, which belong to skeletal CD vibrations, depend on the sizes of the guest molecules. Our results indicate that the formation of the CD inclusion complexes can be followed by VCD spectroscopy.

Vibrational circular dichroism spectroscopy is briefly characterized and its application to stereochemical analysis is described. As examples, determination of absolute configuration of a pharmaceutically interesting precursor of femoxetine, monitoring of conformational changes of the peptide part of porphyrin-polypeptide complexes and of the sol-gel phase-transition process in tetrabrucine-porphyrin system are given.

Absorption and vibrational circular dichroism (VCD) spectra of the title compound, a common intermediate in synthesis of many pharmaceuticals, were measured and analyzed in order to determine its absolute configuration and prevailing conformations. The analysis was combined with a systematic conformer search based on relative energies as well as with comparison of experimental and computed NMR shifts. The spectra were interpreted on the basis of ab initio simulations. The results indicate that the compound adopts exclusively a chair conformation of the piperidine ring with all the fluorophenyl, hydroxymethyl, and methyl substituents attached in equatorial positions. A limited rotation of the hydroxymethyl group is most consistent with the observed VCD pattern. VCD parameters were found significantly more sensitive to conformational changes than absorption or NMR. Concentration dependence of the absorption spectra indicated aggregation in concentrated solutions, but involved hydrogen bonds probably do not influence molecular conformation.

The synthesis of chiral tricyclo[4.3.0.03,8]nonane-4,5-dione was accomplished starting from enantiomerically pure (+)-(1S,5S)-bicyclo[3.3.1]nonane-2,6-dione 1. Ring contraction of the latter with thallium(III) nitrate proceeded with high stereoselectivity giving exclusively methyl (+)-(1S,4S)-(+)-exo,exo-bicyclo[2.2.1]heptan-2,5-dicarboxylate 2. Inversion of the configuration of this diester to the required di-endo derivative was realized via the following reaction sequence. Bromination of the corresponding acid dichloroanhydride and subsequent reduction with zinc in acetic acid gave a diastereoisomeric mixture of esters, from which the endo,endo-ester 5 was isolated by column chromatography. Acyloin condensation of the latter with trimethylchlorosilane in toluene led to intramolecular ring closure, and subsequent oxidation of the enol silyl ether 7 in situ gave tricyclo[4.3.0.03,8]nonane-4,5-dione 8. The chiroptical properties of this cage molecule were studied by electronic and vibrational circular dichroism spectroscopy. The (1R,3R,6R,8R) absolute configuration of the title structure was also unambiguously proved.

The solution structures of (3R,4S)- and (3S,4R)- 4-(4-fluorophenyl)-3-hydroxylmethyl- 1-methylpiperidine, which are intermediates in the synthesis of the two pharmaceuticals paroxetine and femoxetine, were studied by vibrational circular dichroism (VCD) spectroscopy. In addition, six derivatives with different substituents attached to the C3 atom were prepared and their VCD and absorption spectra discussed with the aid of ab initio simulations. The VCD spectra were found to be sensitive to the geometry changes. In addition, a subtle variation caused by intermolecular aggregation was apparent in the spectra. The VCD technique can be applied for structural analysis of chiral pharmaceuticals in solutions.

Noncovalent interactions of poly(L-lysine) (PL), oligopeptides L-lysyl-L-alanyl-L-alanine and (L-lysyl-L-alanyl-L-alanine)(2) with meso-tetrakis(4-sulfonatophenyl)porphine (TPPS), and poly(L-glutamic acid) (PLGA) with meso-tetrakis(1-methyl-4-pyridyl)porphine tetra-p-tosylate (TMPyP) in aqueous solutions have been studied using combination of spectroscopic methods: Vibrational circular dichroism (VCD) spectroscopy in the mid-infrared region provides a direct information on conformational changes of the polypeptides and oligopeptides caused by interactions with porphyrins; ultraviolet-visible absorption, fluorescence, and electronic circular dichroism (ECD) reveal the aggregation characterization of the porphyrin part of the complexes. Interactions of TPPS with tripeptide, hexapeptide, and PL containing about ten amino acid residues in the molecular chain are accompanied with the changes of VCD patterns in the amide I' region. In these cases, the conformation of the oligopeptide part of complexes is obviously influenced by interactions with TPPS and partial changes of random coil structure are observed in VCD. When PL was composed of the hundreds of lysine residues, just a weak intensity decrease was detected and the shape of VCD spectrum typical for the random coil structure was preserved. As follows from the uv-vis absorption and fluorescence spectra, porphyrin molecules are attached to peptides by electrostatic interaction as a monomer or dimer and interaction between porphyrin and peptide depends on the polypeptide chain length. For the PLGA-TMPyP system with PLGA containing from tens to hundreds of glutamic acid residues in the chain, the VCD spectra were unchanged when TMPyP was presented in the aqueous solution of PLGA and random coil conformation of PLGA-TMPyP aggregates was preserved.

Absorption and vibrational circular dichroism (VCD) spectra of six 1, 1'-binaphthyl derivatives were measured and analyzed on the basis of ab initio modeling. The spectra of both enantiomers were recorded with a high signal-to-noise ratio. The BPW91/6-31G** density functional theory level and the gauge invariant atomic orbitals were used for the simulations of VCD intensities. The binaphthyl moiety behaves as a chiral chromophore with a strong VCD signal because the 1,1'-substitution hinders its rotation. Most of the VCD bands were assigned, and the contributions of the binaphthyl skeleton and the functional groups could be clearly distinguished. Distinct VCD characteristics were found for the compounds exhibiting C-2 and C-1 symmetry. A very good agreement between the calculated and experimental spectra was observed. Apart from indication of enantiomeric purity, the spectra contain readable information about molecular conformation. The dihedral angle between the naphthyls planes, equal to about 55 degrees when naphthyl residues were connected with PO4 covalent bridge, was found close to 90 degrees for all the other derivatives.

Vibrational circular dichroism (VCD) spectra of (+)-alpha-pinene solutions in carbon tetrachloride have been measured in the range of volume fractions 5-100% (v/v) in the mid-infrared region. The concentration dependence measured was statistically analyzed with the aim of obtaining a reliable correlation between the VCD band areas and the concentrations of individual enantiomers. The quality of the spectra was estimated by means of noise spectra which were defined as half the difference of the two following blocks of scans. In addition to this, the enantiomeric purity was studied. This study was carried out for both (+)- and (-)-alpha-pinene enantiomers in the range of the percent enantiomeric excess in the interval 10-100%. The relationship between VCD intensity and enantiomeric purity was determined by least-square regression and statistically evaluated. All measurements performed in this study were intended as a basic tool for testing of a new commercial VCD setup from Bruker. Copyright 2000 Wiley-Liss, Inc.

The Raman and absorption spectra of tetraphenylporphyrin (TPP) were calculated and compared to experiment. The computation was based on the harmonic molecular force field and electric tensors obtained ab initio at the BPW91/6-31G* level. Good agreement was found between experimental and calculated frequencies and intensities. In order to estimate whether induced optical activity in chiral complexes interferes with the signal of peptide vibrations, the vibrational circular dichroism (VCD) spectra of TPP were simulated. The magnetic field perturbation theory (MFP) and the gauge-invariant atomic orbitals (GIAO) were used for the simulation. Such spectra were compared to theoretical VCD intensities of a model tripeptide as well to experimental spectra of a complex of the peptide and tetrakis(p-sulfonatophenyl)porphyrin (TSPP). No significant contribution to VCD signal from the TPP residue was found in experimental spectra. Thus, possible peptide conformational changes occurring during the complexation can be monitored directly in the amide I frequency region.

are RR, SS and RS, SR, while RR and RS, for example, are diastereomers and not mirror images. Note that other subtle forms of chirality can occur in molecules without classical asymmetric centers, e.g. octahedral complexes with an appropriate arrangement of ligands, molecules with dis-symmetric perpendicular planes or helix-like structures. In general, enantiomers have identical physical properties, except as described below, and give identical UV, IR, and NMR spectra, while diastereomers have similar but distin-guishable spectroscopic and chemical properties.