Solid-Phase Peptide Modification via Deaminative Photochemical Csp3-Csp3 Bond Formation Using Katritzky Salts

Introduction of unnatural amino acids can significantly improve the binding affinity and stability of peptides. Commercial availability of such amino acids is limited, and their synthesis is a long and tedious process. We here describe a method that allows the functionalization of peptides directly on solid-support by converting lysine residues to Katritzky salts, and subjecting them to a photochemical Giese reaction under mild reaction conditions. The method avoids the need for amino acid synthesis and instead offers a late-stage modification route for rapid peptide diversification. While numerous modification approaches at the lysine amine have been described, this work provides the first example of deaminative functionalization of peptides at lysine. The two-step protocol is compatible with various substrates, lysine analogues, resins, and all proteinogenic amino acids. Finally, by leveraging solid-phase modification, this protocol facilitates the functionalization of longer peptides as was demonstrated using biologically relevant peptides of up to 15 amino acids.     

The Plasma Membrane as a Reservoir,Protective Shield,and Light‐Triggered Launch Pad for Peptide Therapeutics

Although peptide‐based therapeutics are finding increasing application in the clinic, extensive structural modification is typically required to prevent their rapid degradation by proteases in the blood. We have evaluated the ability of erythrocytes to serve as reservoirs, protective shields (against proteases), and light‐triggered launch pads for peptides. We designed lipidated peptides that are anchored to the surface of red blood cells, which furnishes a protease‐resistant environment. A photocleavable moiety is inserted between the lipid anchor and the peptide backbone, thereby enabling light‐triggered peptide release from erythrocytes. We have shown that a cell‐permeable peptide, a hormone (melanocyte stimulating hormone), and a blood‐clotting agent can be anchored to erythrocytes, protected from proteases, and photolytically released to create the desired biological effect.     

Ambient Temperature Ligation of Diene Functional Polymer and Peptide Strands onto Cellulose via Photochemical and Thermal Protocols

In the present contribution, two novel ambient temperature avenues are introduced to functionalize solid cellulose substrates in a modular fashion with synthetic polymer strands (poly(trifluoro ethyl methacrylate), PTFEMA, M_n = 4400 g mol⁻¹, Đ = 1.18) and an Arg‐Gly‐Asp (RGD) containing peptide sequence. Both protocols rely on a hetero Diels–Alder reaction between an activated thiocarbonyl functionality and a diene species. In the first—thermally activated—protocol, the cellulose features surface‐expressed thiocarbonylthio compounds, which readily react with diene terminal macromolecules at ambient temperature. In the second protocol, the reactive ene species are photochemically generated based on a phenacyl sulfide‐decorated cellulose surface, which upon irradiation expresses highly reactive thioaldehyde species. The generated functional hybrid surfaces are characterized in‐depth via ToF‐SIMS and XPS analysis, revealing the successful covalent attachment of the grafted materials, including the spatially resolved patterning of both synthetic polymers and peptide strands using the photochemical protocol. The study thus provides a versatile platform technology for solid cellulose substrate modification via efficient thermal and photochemical ligation strategies.

     

硫代樟脑光化学反应的理论研究

运用量子化学方法优化了硫代樟脑的最低5个电子态(S₀, T₁, S₁, T₂和S₂)的结构, 并计算了它们的相对能量. 计算结果表明: S₁, T₁和T₂态的能量非常接近, 而S₂的能量远远高于T₂态, 这与之前对几种小的硫代羰基化合物的研究结论一致. 确定了硫代樟脑分子在T₁态发生β-插入反应和类Norrish II型反应的机理, 计算的势垒相对于S₀的振动零点分别为314.1和332.6 kJ/mol. 在400 nm波长的光的照射下, 分子被激发到S₁态, 此时分子没有足够的能量发生反应, 只能通过内转换回到基态. 当激发光波长在254 nm时, 硫代樟脑分子被激发到S₂态, 这时候体系有了足够的内部能量使反应发生. 实验上已经观察到此激发光波长下, 气态硫代樟脑可以发生β-插入反应和类Norrish II型反应.     

Peptide Nanotubes

The self‐assembly of different classes of peptide, including cyclic peptides, amyloid peptides and surfactant‐like peptides into nanotube structures is reviewed. The modes of self‐assembly are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.     

Enantioselective Photochemical Organocascade Catalysis

Reported herein is a photochemical cascade process that combines the excited‐state and ground‐state reactivity of chiral organocatalytic intermediates. This strategy directly converts racemic cyclopropanols and α,β‐unsaturated aldehydes into stereochemically dense cyclopentanols with exquisite stereoselectivity. Mechanistic investigations have enabled elucidating the origin of the stereoconvergence, which is governed by a kinetic resolution process.     

A Theoretical Study of Photochemical Reaction for Synthesis of Thiirane

The geometrical configurations of the products in reaction of sulfur and ethylene are optimized by use of UHF method and 3-21G basis sets and the potential energy surfaces for resulting thiirane are calculated using STO-3G + CI(100×100) . The possibilities of obtaining the thiirane on the surfaces of low-lying excited states are discussed. The energies of low-lying excited states of thiirane and the corresponding configurations are predicted by using 4-31G basis sets + CI(100×100) finally.     

An Unprecedented Photochemical Reaction for Anthracene‐Containing Derivatives

A series of anthracene‐containing derivatives have been synthesised and characterised. The photochemical behaviour of these derivatives have been investigated by ¹H NMR spectroscopy. An unprecedented photolysis reaction for anthracene‐containing derivatives was observed in the case of anthracenes directly armed with a ‐CH₂O‐R group upon UV irradiation. The photolysis reaction process has been demonstrated to occur in three steps. Firstly, the anthracene‐containing derivatives are converted into the corresponding endoperoxide intermediate upon UV irradiation in the presence of air; then, the endoperoxide intermediate is decomposed to the corresponding starting compound and 9‐anthraldehyde; finally, 9‐anthraldehyde is further oxidised to anthraquinone. Additionally, the photolysis reaction of anthracene‐containing derivatives is significantly promoted in the presence of a thiacalix[4]arene platform.     

Enantioselective Catalysis of Photochemical Reactions

The nature of the excited state renders the development of chiral catalysts for enantioselective photochemical reactions a considerable challenge. The absorption of a 400 nm photon corresponds to an energy uptake of approximately 300 kJ mol^?1. Given the large distance to the ground state, innovative concepts are required to open reaction pathways that selectively lead to a single enantiomer of the desired product. This Review outlines the two major concepts of homogenously catalyzed enantioselective processes. The first part deals with chiral photocatalysts, which intervene in the photochemical key step and induce an asymmetric induction in this step. In the second part, reactions are presented in which the photochemical excitation is mediated by an achiral photocatalyst and the transfer of chirality is ensured by a second chiral catalyst (dual catalysis).     

对位取代酚类物质的光化学荧光测定研究

指出了碱性介质中，对羟基苯乙酸、对羟基苯丙酸、高香草酸、对甲基酚和补势息痛等对位取代酚类物质的溶液，在光照下发生自氧化还原反应，产生荧光二聚体，此二聚体与酶反应产物具有相的荧光光谱行为。在不同介质中，二聚体的生成速率及其荧光强度明显不同。     

Recent Developments in the Photochemical Synthesis of Functionalized Imidazopyridines

Imidazopyridines constitute one of the most important scaffolds in medicinal chemistry, as their skeleton could be found in a myriad of biologically active molecules. Although numerous strategies were elaborated for imidazopyridine preparation in the 2010s, novel eco-compatible synthetic approaches have emerged, conscious of climate change concerns. In this framework, photochemical methods have been promoted to conceive this heterocyclic motif over the last decade. This review covers the recently published works on synthesizing highly functionalized imidazopyridines by light induction.     

Precipitation Under Homogeneous or Heterogeneous Conditions by Photochemical Action

Abstract

Precipitation reagents may be formed in situ by photochemistry but the formation cannot be completely homogeneous due to the exponential nature of light absorption (Beer's Law). By proper adjustment of concentrations, one may vary the conditions from near homogeneous to heterogeneous formation of photoprecipitate.     

磷的光化学分析新方法研究

在０．２ｍｏｌ／ＬＨ２ＳＯ４－１０％乙醇介质中及紫外光照射条件下磷钼杂多酸光还原为磷钼蓝（λｍａｘ＝７８０ｎｍ）。据此建立了一个测定０．０５～２．０μｇ／ｍＬ磷的光化学分析新方法，并用于试样分析。探讨了光化学反应机理。     

Pigment–Acceptor–Catalyst Triads for Photochemical Hydrogen Evolution

In order to solve the problems of global warming and shortage of fossil fuels, researchers have been endeavoring to achieve artificial photosynthesis: splitting water into H₂ and O₂ under solar light illumination. Our group has recently invented a unique system that drives photoinduced water reduction through “Z‐scheme” photosynthetic pathways. Nevertheless, that system still suffered from a low turnover number (TON) of the photocatalytic cycle (TON=4.1). We have now found and describe herein a new methodology to make significant improvements in the TON, up to around TON=14–27. For the new model systems reported herein, the quantum efficiency of the second photoinduced step in the Z‐scheme photosynthesis is dramatically improved by introducing multiviologen tethers to temporarily collect the high‐energy electron generated in the first photoinduced step. These are unique examples of “pigment–acceptor–catalyst triads”, which demonstrate a new effective type of artificial photosynthesis.     

Photochemical Construction of Carbonitride Structures for Red‐Light Redox Catalysis

Metal‐free carbonitride(CN) semiconductors are appealing light‐transducers for photocatalytic redox reactions owing to the unique band gap and stability. To harness solar energy efficiently, CN catalysts that are active over a wider range of the visible spectrum are desired. Now a photochemical approach has been used to prepare a new‐type triazine‐based CN structure. The obtained CN shows extraordinary light‐harvesting characteristics, with suitable semiconductor‐redox potentials. The light absorption edge of the CN reaches up to 735 nm, which is significantly longer than that of the conventional CN semiconductor at about 460 nm. As expected, the CN can efficiently catalyze oxidation of alcohols and reduction of CO₂ with visible light, even under red‐light irradiation. The results represent an important step toward the development of red‐light‐responsive triazine‐based structures for solar applications.