Synthesis and complexes of a constrained-cavity Schiff-base dipyrrin macrocycle

A new constrained-cavity [1 + 1] Schiff-base dipyrrin macrocycle comprising an N4 donor-pocket has been synthesised by spontaneous oxidation and in situ crystallisation. Access to Fe(ii) and Zn(ii) complexes is achieved by salt elimination reactions of the lithium salt. All compounds have been characterised by NMR and UV-vis spectroscopy, X-ray crystallography, and DFT analysis.

Disambiguating "Mechanisms" in Pharmacy: Lessons from Mechanist Philosophy of Science

Talk of mechanisms is ubiquitous in the natural sciences. Interdisciplinary fields such as biochemistry and pharmacy frequently discuss mechanisms with the assistance of diagrams. Such diagrams usually depict entities as structures or boxes and activities or interactions as arrows. While some of these arrows may indicate causal or componential relations, others may represent temporal or operational orders. Importantly, what kind of relation an arrow represents may not only vary with context but also be underdetermined by empirical data. In this manuscript, we investigate how an analysis of pharmacological mechanisms in terms of producing and underlying mechanisms-as discussed in the contemporary philosophy of science-may shed light on these issues. Specifically, we shall argue that while pharmacokinetic mechanisms usually describe causal chains of production, pharmacodynamics tends to focus on mechanisms of action underlying the in vivo effects of a drug. Considering the action of thyroid gland hormones in the human body as a case study, we further demonstrate that pharmacodynamic schemes tend to incorporate entities and interactions on multiple levels. Yet, traditional pharmacodynamic schemes are sketched "flat", i.e., non-hierarchically. We suggest that transforming flat pharmacodynamic schemes into mechanistic multi-level representations may assist in disentangling the different kinds of mechanisms and relations depicted by arrows in flat schemes. The resulting Baumkuchen model provides a powerful and practical alternative to traditional flat schemes, as it explicates the relevant mechanisms and relations more clearly. On a more general note, our discussion demonstrates how pharmacology and related disciplines may benefit from applying concepts from the new mechanist philosophy to guide the interpretation of scientific diagrams.

Cross-β amyloid nanotubes for hydrolase-peroxidase cascade reactions

Herein, we report the catalytic potential of short peptide based cross-β amyloid nanotubes with surface exposed histidine capable of binding hemin and showing facile cascade reactions, playing the dual roles of hydrolases and peroxidases, two of the most important classes of enzymes in extant biology. The activity of these simple systems exceeded those of modern and larger proteins like cytochrome C and hemoglobin. Further, evidence suggested that these self-assembled nanotubes foreshadow the process of intermediate channeling, a feature seen in the case of advanced enzymes.

Water/Alkali-Catalyzed Reactions of Azides with 2-Cyanothioacetamides. Eco-Friendly Synthesis of Monocyclic and Bicyclic 1,2,3-Thiadiazole-4-carbimidamides and 5-Amino-1,2,3-triazole-4-carbothioamides

The reactions of thioamides with azides in water were studied. It was reliably shown that the reaction of 2-cyanothioacetamides 1 with various types of azides 2 in water in the presence of alkali presents an efficient, general, one-step, atom-economic, and eco-friendly method for the synthesis of 1,2,3-thiadiazol-4-carbimidamides 5 and 1,2,3-triazole-4-carbothioamides 4. This method can be extended to the one-pot reaction of sulfonyl chlorides and 6-chloropyrimidines 2'o with sodium azide, leading to final products in higher yields, that is, avoiding the isolation of unsafe sulfonyl azides. The method was furthermore applied to the reaction of N,N'-bis-(2-cyanothiocarbonyl)pyrazine 1h with sulfonyl azides to afford bicyclic 1,2,3-thiadiazoles 8 and 1,2,3-triazoles 9 connected via a 1,1'-piperazinyl linker. 2-Cyanothioacetamides 1 were also shown to react with aromatic azides in water in the presence of alkali to afford 1-aryl-5-amino-1,2,3-triazole-4-carbothioamides 11. In contrast to aromatic azides and similarly to sulfonyl azides, 6-azidopyrimidine-2,4-diones 2o-q react with cyanothioacetamides to form N-pyrimidin-6-yl-5-dialkylamino-1,2,3-thiadiazole-4-N-l-carbimidamides 12. A mechanism was proposed to rationalize the role of water in changing the reactivity of azides toward 2-cyanothioacetamides.

Stabilization of Supramolecular Networks of Polyiodides with Protonated Small Tetra-azacyclophanes

Polyiodide chemistry is among the first historically reported examples of supramolecular forces at work. To date, owing to the increasingly recognized role of halogen bonding and the incorporation of iodine-based components in several devices, it remains an active field of theoretical and applied research. Herein we re-examine azacyclophanes as a class of ligands for the stabilization of iodine-dense three-dimensional networks, showing how we devised novel possible strategies starting from literature material. The new set of azacyclophane ligands affords novel crystal structures possessing intriguing properties, which develop on a double layer. At a macroscopic level, the obtained networks possess a very high iodine packing density (less than 2 times more diluted than crystalline I2): a simple parameter, IN, is also introduced to quickly measure and compare iodine packing density in different crystals. On the microscopic level, the present study provides evidence about the ability of one of the ligands to act as a three-dimensional supramolecular mold for the template synthesis of the rarely observed heptaiodide (I7−) anion. Therefore, we believe our approach and strategy might be relevant for crystal engineering purposes.

Electronic Structure and Spin Multiplicity of Iron Tetraphenylporphyrins in Their Reduced States as Determined by a Combination of Resonance Raman Spectroscopy and Quantum Chemistry

Iron tetraphenylporphyrins are prime candidates as catalysts for CO₂ reduction. Yet, even after 40 years of research, fundamental questions about the electronic structure of their reduced states remain, in particular as to whether the reducing equivalents are stored at the iron center or at the porphyrin ligand. In this contribution, we address this question by a combination of resonance Raman spectroscopy and quantum chemistry. Analysis of the data allows for an unequivocal identification of the porphyrin as the redox active moiety. Additionally, determination of the spin state of iron is possible by comparing the characteristic shifts of spin and oxidation-state-sensitive marker bands in the Raman spectrum with calculations of planar porphyrin model structures.

N-(4-Hydroxyphenyl)acetamide against diiodine towards polyiodide dianion

N-(4-Hydroxyphenyl)acetamide decreases the total amount of diiodine which is available for the iodination of tyrosil residues of thyroglobulin, while it inhibits the activity of thyroid peroxidase.

Halogen bonds with coordinative nature: halogen bonding in a S–I+–S iodonium complex

A thorough characterization of unusually strong I⁺–S halogen bonds indicates that halogen bonding is not merely an electrostatic contact but also has a strong coordinative nature, thus expanding the scope of halogen bonding.

Indium-catalyzed microwave-accelerated pot economic C–C bond formation process towards the ‘dry-media’ synthesis of pyrimidine derivatives

Substituted pyrimidines can be constructed in good yields via a microwave-accelerated C–C bond formation process through Lewis acid catalysed Diels–Alder reaction from easily available uracil diene and electron deficient acetylene carboxylate.

Modification of the supramolecular structure of [(thione)IY] (Y = Cl, Br) systems by cooperation of strong halogen bonds and hydrogen bonds

Strong halogen bonds and hydrogen bonds cooperated to control the supramolecular structures of [(thione)IY] (Y = Cl, Br) compounds.

Fundamental chemistry of iodine. The reaction of di-iodine towards thiourea and its methyl-derivative: formation of aminothiazoles and aminothiadiazoles through dicationic disulfides

The reactivity of di-iodine towards thiourea (TU) and its derivative methylthiourea (MeTU) is studied. A diversity of products was obtained from these reactions.