Detailed structural and spectroscopic elucidation of ferrocenium coupled N-heterocyclic carbene gold(i) complexes

Unambiguous assignment of redox sites on ferrocene coupled N-heterocyclic carbene gold(i) anticancer therapeutic agents is described.

The K. Thomas - R. Kilmann questionnaire: the vulnerabilities of the diagnostic tool

The results of the analysis of the text of the K. Thomas - R. Kilmann questionnaire are presented. It is shown that the formulation of many items is not specific for their unambiguous assignment to the prescribed scales. In some formulations, the context of the mode of behavior that is proposed to be chosen is not clearly defined. In many of the pairs of statements, the options are difficult to distinguish from each other or are not strictly alternative. The directions of work for overcoming the identified vulnerabilities of the questionnaire are proposed.

Total Synthesis and Structural Reassignment of Laingolide A

The asymmetric total synthesis of four diastereomers of laingolide A was achieved, which led to the unambiguous assignment of the stereochemistry of the natural product. The salient features of the convergent, fully stereocontrolled approach were a copper-catalysed stereospecific Kumada-type coupling, a Julia-Kocienski olefination and an RCM/alkene migration sequence to access the desired macrocyclic enamide.

A phasianid bird from the Pleistocene of Tainan: the very first avian fossil from Taiwan

Taiwan accommodates more than 600 avian species, including about 30 endemic ones. As yet, however, no fossil birds have been scientifically documented from Taiwan, so that the evolutionary origins of this diversified avifauna remain elusive. Here we report on the very first fossil bird from Taiwan. This Pleistocene specimen, a distal end of the left tarsometatarsus, shows diagnostic features of the galliform Phasianidae, including an asymmetric plantar articular facet trochlea metatarsi III. Our discovery of a Pleistocene phasianid from Taiwan opens a new perspective on studies of the evolution of the avifauna in Taiwan because the fossil shows that careful search for fossils in suitable localities has the potential of recovering avian remains. In general, East Asia has an extremely poor avian fossil record, especially if terrestrial birds are concerned, which impedes well-founded evolutionary scenarios concerning the arrival of certain groups in the area. The Phasianidae exhibit a high degree of endemism in Taiwan, and the new fossil presents the first physical evidence for the presence of phasianids on the island, some 400,000–800,000 years ago. The specimen belongs to a species the size of the three larger phasianids occurring in Taiwan today (Syrmaticus mikado, Lophura swinhoii, and Phasianus colchicus). Still, an unambiguous assignment to either of these species is not possible due to the incomplete nature of the left tarsometatarsus. Because the former two species are endemic to Taiwan, the fossil has the potential to yield the first data on their existence in the geological past of Taiwan if future finds allow identification on species-level.

Assignment of Absolute Configuration of Bromoallenes by Vacuum-Ultraviolet Circular Dichroism (VUVCD)

A new application of vacuum-ultraviolet circular dichroism (VUVCD), which enables the measurement of CD spectra in the vacuum-ultraviolet region (140–200 nm), for the assignment of the absolute configurations of bromoallenes is described. Bromoallene moieties are found in natural products obtained from many marine organisms. To date, the absolute configuration of bromoallenes has been assigned almost exclusively with Lowe’s rule, which is based on specific rotation. However, exceptions to Lowe’s rule have been reported arising from the presence of other substituents with large specific rotations. For the unambiguous assignment of the absolute configuration of the bromoallene moiety with its characteristic absorption wavelength at 180–190 nm due to the π–π* transition, VUVCD was applied to four pairs of bromoallene diastereomers prepared by modifying the synthetic scheme of omaezallene. The VUVCD spectra clearly showed positive or negative Cotton effects around 180–190 nm according to the configuration of the bromoallene employed, revealing the potential of VUVCD for determining absolute stereochemistry.

Interplay between Oxo and Fluoro in Vanadium Oxyfluorides for Centrosymmetric and Non-Centrosymmetric Structure Formation

Herein, we report the syntheses of two lithium-vanadium oxide-fluoride compounds crystallized from the same reaction mixture through a time variation experiment. A low temperature hydrothermal route employing a viscous paste of V2O5, oxalic acid, LiF, and HF allowed the crystallization of one metastable phase initially, Li2VO0.55(H2O)0.45F5⋅2H2O (I), which on prolonged heating transforms to a chemically similar yet structurally different phase, Li3VOF5 (II). Compound I crystallizes in centrosymmetric space group, I2/a with a = 6.052(3), b = 7.928(4), c = 12.461(6) Å, and β = 103.99(2)°, while compound II crystallizes in a non-centrosymmetric (NCS) space group, Pna21 with a = 5.1173(2), b = 8.612(3), c = 9.346(3) Å. Synthesis of NCS crystals are highly sought after in solid-state chemistry for their second-harmonic-generation (SHG) response and compound II exhibits SHG activity albeit non-phase-matchable. In this article, we also describe their magnetic properties which helped in unambiguous assignment of mixed valency of V (+4/+5) for Li2VO0.55(H2O)0.45F5⋅2H2O (I) and +4 valency of V for Li3VOF5 (II).

Być w mówieniu i być mówionym – o teorii języka Jacques’a Lacana i jej konsekwencjach dla podmiotowości

It seems rather obvious that Jacques Lacan’s theory is Freudian psychoanalysis combined with structural linguistics. But it is not so conclusive: in Lacan’s work we can find many elements with different origins to linguistics. Moreover, Lacan’s subversion of structuralist theses makes any unambiguous assignment impossible. In the article, the author describes the evolution of Lacan’s theory of language and its consequences for the issue of subjectivity in psychoanalysis resulting from the use of linguistic tools.

Vibrational Dynamics of Crystalline 4-Phenylbenzaldehyde from INS Spectra and Periodic DFT Calculations

The present work emphasizes the value of periodic density functional theory (DFT) calculations in the assessment of the vibrational spectra of molecular crystals. Periodic calculations provide a nearly one-to-one match between the calculated and observed bands in the inelastic neutron scattering (INS) spectrum of crystalline 4-phenylbenzaldehyde, thus validating their assignment and correcting previous reports based on single molecule calculations. The calculations allow the unambiguous assignment of the phenyl torsional mode at ca. 118–128 cm−1, from which a phenyl torsional barrier of ca. 4000 cm−1 is derived, and the identification of the collective mode involving the antitranslational motion of CH···O bonded pairs, a hallmark vibrational mode of systems where C-H···O contacts are an important feature.

Stereoelectronic Effects Impact Glycan Recognition

Recognition of distinct glycans is central to biology, and lectins mediate this function. Lectin glycan preferences are usually centered on specific monosaccharides. In contrast, human intelectin-1 (hItln-1, also known as Omentin-1) is a soluble lectin that binds a range of microbial sugars, including β-Dgalactofuranose (β-Galf), D-glycerol 1-phosphate, D-glycero-D-talo-oct-2-ulosonic acid (KO), and 3- deoxy-D-manno-oct-2-ulosonic acid (KDO). Though these saccharides differ dramatically in structure, they share a common feature—an exocyclic vicinal diol. How and whether such a small fragment is sufficient for recognition was unclear. We tested several glycans with this epitope and found that L-glycero-α-Dmanno- heptose and D-glycero-α-D-manno-heptose possess the critical diol motif yet bind weakly. To better understand hItln-1 recognition, we determined the structure of the hItln-1·KO complex using X-ray crystallography, and our 1.59-Å resolution structure enabled unambiguous assignment of the bound KO conformation. This carbohydrate conformation was present in >97% of the KDO/KO structures in the Protein Data Bank. Bioinformatic analysis revealed that KO and KDO adopt a common conformation, while heptoses prefer different conformers. The preferred conformers of KO and KDO favor hItln-1 engagement, but those of the heptoses do not. Natural bond orbital (NBO) calculations suggest these observed conformations, including the side chain orientations, are stabilized by not only steric but also stereoelectronic effects. Thus, our data highlight a role for stereoelectronic effects in dictating the specificity of glycan recognition by proteins. Finally, our finding that hItln-1 avoids binding prevalent glycans with a terminal 1,2 diol (e.g., NeuAc, and L-glycero-α-D-manno-heptose) suggests the lectin has evolved to recognize distinct bacterial species.