Synlett最新文献

The modification of biomolecules, particularly peptides, has garnered considerable attention from researchers, effectively serving as a connection between chemistry and biology. The modification of peptides can facilitate, among others, the generation of peptide drugs, antibody–drug conjugates, and probes for molecular imaging. Herein, we have carefully curated reactions and chemical transformations of bioactive peptide sequences equipped with histidine amino acids that are conducive for biological applications. This Account also highlights strategies for the chemical modification of histidine that might capture the imagination of both peptide researchers and synthetic chemists.

1 Introduction

2 Histidine Modification in Bioactive Peptides and Proteins

3 Remote Bioactive Peptides and Protein Modification Adjacent to Histidine

4 Conclusions and Future Directions

Propylene liquid-phase epoxidation with 50–75% H₂O₂ is an important process for the industrial production of propylene oxide (PO). To realize a propylene epoxidation process that proceeds with low hydrogen peroxide concentration, we developed an integrated Mn/TS-1/N catalytic system via in-situ reaction of Mn/TS-1 with an N-donor ligand, affording the PO product in excellent yield with only 30 wt% H₂O₂. Other long-chain aliphatic epoxides were also readily synthesized by this catalytic epoxidation system. Moreover, in addition to the standard micro-pressure reactor, a continuous-flow microreactor was developed that executed the hydrogen peroxide propylene oxide (HPPO) process with excellent efficiency for 1300 hours. This innovative Mn/TS-1/N catalyzed epoxidation represents a promising direction for advancing HPPO industrial processes, offering improved efficiency while minimizing the reliance on high concentrations of H₂O₂.

A simple, efficient, and environmentally benign method for the direct C-3-alkoxycarbonylation of 2H-indazoles using alkyl carbazates has been developed under metal-free conditions at room temperature. This current protocol represents a facile access to C-3-carboxylic ester derived 2H-indazoles with wide functional group tolerance in good to excellent yields. The mechanistic studies suggest that the reaction proceeds through a radical pathway.

Here we describe a homocoupling reaction of arylboronic acid facilitated by silver carbonate, which proceeds smoothly in MeOH even at ambient temperature. The reaction exhibits broad functional group compatibility, affording a variety of symmetrical biaryls in satisfactory yields. Silver nanoparticles formed in situ serve as an accelerator in this process. Moreover, initial mechanistic investigations suggest that this transformation may occur via a radical mechanism.

Pyrazoloindolones are synthesized from N-tosylhydrazones in a one-pot multistep process which include base-promoted (i) electrocyclization reaction of N-tosylhydrazones derived from α,β-unsaturated aldehydes, (ii) aromatic nucleophilic substitution, and (iii) a domino cyclization–oxidation process under aerobic conditions.

The catalytic intermolecular cyclization of thiophenols with allylic alcohols in the presence of bismuth triflate afforded the corresponding thiochromane derivatives in a one-pot reaction. The Bi(OTf)₃-catalyzed reaction was also applied to the intermolecular cyclization of diaryl disulfides with 3-methylbut-2-en-1-ol to produce the corresponding thiochromanes.

A convergent approach to the forskolin skeleton is described. Assembly of a simplified tricyclic framework is achieved in a single step via the dihydropyrone Diels–Alder reaction. Selective manipulation of the resulting cycloadduct, in conjunction with an unusual equilibration of the C8 stereocenter, provides access to scaffolds that differ in relative stereochemistry at both the A/B and B/C ring junctions.

Hydrazine and its derivatives have served as a conventional bipropellant fuel for several decades. However, their extremely acute toxicity and carcinogenicity, high volatility, and environmental impact have attracted significant attention. In order to synthesize green bipropellant fuels with high density, high specific impulse, and good thermal stability, three novel N-alkyl-1,2,4-triazole–borane complexes were successfully synthesized by reacting alkylated 1,2,4-triazole coordinated with sodium borohydride in the presence of ammonium sulfate. During the droplet test with white fuming nitric acid, there was a relatively short ignition delay time of 98 ms. Additionally, these hypergolic fuels possessed a high density exceeding 1.10 g cm^–3, and the specific impulse is ranging from 187 to 199 s, and the highest decomposition temperature reaches 153.4 °C. These results demonstrate their great potential as hypergolic fuels or hypergolic ionic liquid additives in the field of hypergolic materials.

A palladium-catalyzed β-C(sp³)–H arylation of aliphatic ketones by using acetohydrazide as a transient directing group has been developed. The reaction proceeds through a less-favored [5,5]-bicyclic palladacycle intermediate and is promoted by a pyridine ligand.

An efficient and practical method for the bromination of electron-rich arenes and heteroarenes was developed by using S-methyl methanethiosulfonate as the oxidant. All the bromine atoms were basically transferred to the brominated products, demonstrating the exceptional atom economy and practicality of the proposed protocol. The method reduces the amount of bromine required for this reaction system and obtains products in moderate to good yields.