Synthesis of 4,5-dihydrofuran derivatives by the reaction of acetoacetic ester with conjugated alkenynes

The regiochemistry of the reaction of acetoacetic ester with vinylacetylene, isopropenylacetylene, and vinylisopropenylacetylene in the presence of the manganese acetate/copper acetate oxidative system was studied. Derivatives of furan and 4,5-dihydrofuran were obtained as a result of oxidative cyclization of intermediate radicals that contain unsaturated groups in the position. Data from the IR, UV, PMR, ¹³C NMR, and mass spectra of the synthesized compounds are presented.Communication 75 from the series Reactions of Unsaturated Compounds. See [1] for Communication 74.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 19–23, January, 1982.     

Synthesis of 4,5-dih ydrofuran derivatives by the reaction of acetylace tone with conjugated alkenes

The reaction of the acetylacetonyl radical (generated from acetylacetone by the action of manganese acetate) with vinylacetylene, 2-vinylfuran, and butadiene Was studied. The reaction proceeds nonregioselectively with vinylacetylene: 3-acetyl-2-methyl-5-ethynyl- and 3-acetyl-2-methyl-5-(4-acetyl-5-methyl-2-furyl)-4,5-dihydrofurans in a ratio of 12.2 were isolated. The principal products in the reaction with 2-vinylfuran and butadiene were 3-acetyl-2-methyl-5-(2-furyl)- and 3-acetyl-2-methyl-5-vinyl-4,5-dihydrofurans.Communication 62 from the series Reactions of unsaturated compounds. See [1] for communication 61.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 884–887, July, 1980.     

Direct Photocontrol of Peptidomimetics: An Alternative to Oxygen‐Dependent Photodynamic Cancer Therapy

Conventional photodynamic treatment strategies are based on the principle of activating molecular oxygen in situ by light, mediated by a photosensitizer, which leads to the generation of reactive oxygen species and thereby causes cell death. A diarylethene‐derived peptidomimetic is presented that is suitable for photodynamic cancer therapy without any involvement of oxygen. This light‐sensitive molecule is not a mediator but is itself the cytotoxic agent. As a derivative of the cyclic amphiphilic peptide gramicidin S, the peptidomimetic exists in two thermally stable photoforms that are interconvertible by light of different wavelengths. The isomer generated by visible light shows much stronger toxicity against tumor cells than the UV‐generated isomer. First in vivo applications are demonstrated on a tumor animal model to illustrate how the peptidomimetic can be administered in the less toxic form and then activated locally in a solid tumor by visible light.     

Design,Synthesis, and Application of an Optimized Monofluorinated Aliphatic Label for Peptide Studies by Solid‐State 19F NMR Spectroscopy

A conformationally restricted monofluorinated α‐amino acid, (3‐fluorobicyclo[1.1.1]pentyl)glycine (F‐Bpg), was designed as a label for the structural analysis of membrane‐bound peptides by solid‐state ¹⁹F NMR spectroscopy. The compound was synthesized and validated as a ¹⁹F label for replacing natural aliphatic α‐amino acids. Calculations suggested that F‐Bpg is similar to Leu/Ile in terms of size and lipophilicity. The ¹⁹F NMR label was incorporated into the membrane‐active antimicrobial peptide PGLa and provided information on the structure of the peptide in a lipid bilayer.     

Diffusion of Oligonucleotides from within Iron‐Cross‐Linked,Polyelectrolyte‐Modified Alginate Beads: A Model System for Drug Release

An analytical model to describe diffusion of oligonucleotides from stable hydrogel beads is developed and experimentally verified. The synthesized alginate beads are Fe³⁺‐cross‐linked and polyelectrolyte‐doped for uniformity and stability at physiological pH. Data on diffusion of oligonucleotides from inside the beads provide physical insights into the volume nature of the immobilization of a fraction of oligonucleotides due to polyelectrolyte cross‐linking, that is, the absence of a surface‐layer barrier in this case. Furthermore, the results suggest a new simple approach to measuring the diffusion coefficient of mobile oligonucleotide molecules inside hydrogels. The considered alginate beads provide a model for a well‐defined component in drug‐release systems and for the oligonucleotide‐release transduction steps in drug‐delivering and biocomputing applications. This is illustrated by destabilizing the beads with citrate, which induces full oligonucleotide release with nondiffusional kinetics.     

Cu-Catalyzed Arylation of Bromo-Difluoro-Acetamides by Aryl Boronic Acids,Aryl Trialkoxysilanes and Dimethyl-Aryl-Sulfonium Salts: New Entries to Aromatic Amides

We describe a mechanism-guided discovery of a synthetic methodology that enables the preparation of aromatic amides from 2-bromo-2,2-difluoroacetamides utilizing a copper-catalyzed direct arylation. Readily available and structurally simple aryl precursors such as aryl boronic acids, aryl trialkoxysilanes and dimethyl-aryl-sulfonium salts were used as the source for the aryl substituents. The scope of the reactions was tested, and the reactions were insensitive to the electronic nature of the aryl groups, as both electron-rich and electron-deficient aryls were successfully introduced. A wide range of 2-bromo-2,2-difluoroacetamides as either aliphatic or aromatic secondary or tertiary amides were also reactive under the developed conditions. The described synthetic protocols displayed excellent efficiency and were successfully utilized for the expeditious preparation of diverse aromatic amides in good-to-excellent yields. The reactions were scaled up to gram quantities.     

Enantioselective Guest Effect on the Spin State of a Chiral Coordination Framework

The diversity of spin crossover (SCO) complexes that, on the one hand, display variable temperature, abruptness and hysteresis of the spin transition, and on the other hand, are spin‐sensitive to the various guest molecules, makes these materials unique for the detection of different organic and inorganic compounds. We have developed a homochiral SCO coordination polymer with a spin transition sensitive to the inclusion of the guest 2‐butanol, and these solvates with (R)‐ and (S)‐alcohols demonstrate different SCO behaviours depending on the chirality of the organic analyte. A stereoselective response to the guest inclusion is detected as a shift in the temperature of the transition both from dia‐ to para‐ and from para‐ to diamagnetic states in heating and cooling modes respectively. Furthermore, the Mössbauer spectroscopy directly visualizes how the metallic centres in a chiral coordination framework differently sense the interaction with guests of different chiralities.     

The Rb7Bi3−3xSb3xCl16 Family: A Fully Inorganic Solid Solution with Room-Temperature Luminescent Members

Low-dimensional ns²-metal halide compounds have received immense attention for applications in solid-state lighting, optical thermometry and thermography, and scintillation. However, these are based primarily on the combination of organic cations with toxic Pb²⁺ or unstable Sn²⁺, and a stable inorganic luminescent material has yet to be found. Here, the zero-dimensional Rb₇Sb₃Cl₁₆ phase, comprised of isolated [SbCl₆]³⁻ octahedra and edge-sharing [Sb₂Cl₁₀]⁴⁻ dimers, shows room-temperature photoluminescence (RT PL) centered at 560 nm with a quantum yield of 3.8±0.2 % at 296 K (99.4 % at 77 K). The temperature-dependent PL lifetime rivals that of previous low-dimensional materials with a specific temperature sensitivity above 0.06 K⁻¹ at RT, making it an excellent thermometric material. Utilizing both DFT and chemical substitution with Bi³⁺ in the Rb₇Bi_3−3xSb_3xCl₁₆ (x≤1) family, we present the edge-shared [Sb₂Cl₁₀]⁴⁻ dimer as a design principle for Sb-based luminescent materials.