Chinese Journal of Chemistry最新文献

Acinetobacter baumannii infections pose a great threat to public health owing to upsurging antibiotic resistance. Capsular polysaccharides (CPS) are major virulence determinants of pathogenic bacteria and have attracted much attention as potential targets for vaccine development. However, the obtainability of structurally well-defined CPS-related oligosaccharides remains challenging. Herein, we report an efficient chemoenzymatic strategy for the first total synthesis of common CPS pentasaccharide repeating unit of Acinetobacter baumannii K27 and K44, containing a difficult-to-construct α-linked 5,7-di-N-acetyllegionaminic acid (Leg5,7Ac₂) residue. The chemical synthesis of a branched tetrasaccharide precursor was accomplished by flexible orthogonal protecting-group manipulations and stereocontrolled glycosylations. Furthermore, the enzyme-catalyzed stereoselective installment of legionaminic acid residue into the tetrasaccharide, using one-pot multienzyme (OPME) synthesis system to produce sugar nucleotide CMP-Leg5,7diN₃ and subsequent α2,6-sialyltransferase-catalyzed glycosylation, was achieved to synthesize the pentasaccharide.

The ternary strategy has demonstrated its efficacy in improving charge transport in organic solar cells (OSCs). Here, three novel non-fullerene acceptors, SN6C9-4F, SN6C9-4Cl and SN6C10-4F, based on S,N-heteroacene linear backbone were designed and synthesized. The three acceptors exhibit excellent molecular coplanarity, high crystallinity and possess a deep-lying lowest unoccupied molecular orbital energy level, which is beneficial for charge transport and injection in organic field-effect transistors (OFETs). Notably, the OFET devices based on all three acceptors achieved impressive electron mobilities, with SN6C10-4F achieving up to 0.73 cm²·V^–1·s^–1, which is one of the highest values among A-D-A type small molecules. In addition, the OSCs device based on PBDB-T:SN6C9-4F exhibited the best power conversion efficiency of 12.07% owing to its optimal morphology and enhanced charge transport. Moreover, the incorporation of SN6C9-4F into the efficient PM6:L8-BO binary system to form ternary OSCs resulted in extended absorption range, enhanced donor crystallization, improved and more balanced charge transport, ultimately leading to an improvement of PCE from 17.78% to 18.32%. This study highlights the potential of developing acceptors with distinct structures from Y-series acceptors to broaden absorption and regulate donor crystallization, providing a novel approach to enhance the PCE of OSCs.

The simultaneous construction of two vicinal C—C bonds in a molecule remains a significant challenge. In this work, we disclose an electroreductive carboarylation of activated alkenes under mild, transition metal-free conditions. Utilizing readily available starting materials (electron-deficient aryl bromides, activated alkenes, and CO₂), this method demonstrates broad substrate scope and good functional group tolerance. Notably, this strategy enables the addition of two distinct electrophiles across an alkene in a highly chemo- and regioselective manner.

Electron transfer is an important way to activate persulfate. Currently, the electrons for persulfate activation mainly originate from organic contaminants or the catalyst itself, which can lead to selective activation of persulfate or oxidation of the catalyst, respectively, and thus become a bottleneck restricting its application. In this work, Cu−doped FeVO₄ (Cu−FVO) was prepared, and the results showed that Cu doping can significantly improve the photocatalytic activity and stability of FVO for peroxymonosulfate (PMS) activation. The optimized Cu−FVO/PMS/light system exhibited a high BPA degradation rate that is 4.3 times higher than that of the FVO/PMS/light. This system manifested a broad applicability to various organic contaminants even with complex matrix. Photoelectrochemical analysis and DFT theoretical calculations revealed that Cu doping boosted the photogenerated charge separation and the adsorption of PMS on FVO. Furthermore, Cu doping led to the establishment of an electron transfer channel from Cu−FVO to PMS, through which photogenerated electrons achieved an efficient PMS activation. Meanwhile, holes were consumed by organic contaminants to avoid the oxidation of catalyst. These collectively enhanced the photocatalytic activity and stability of Cu−FVO, which also maintained high catalytic activity even after 20 cycling degradation reactions.

Five unreported and oxygenated ent-rosane diterpenoids (ent-RDs), Euphomillanols A—E (1—5), were isolated from Euphorbia milii. Among them, compounds 1 and 2 are unprecedented 7/7/6-fused tricyclic 5,10-seco-ent-RDs and possess a unique 11-oxabicyclo[4.4.1]undeca-1(10),5-diene moiety, while 3 is characterized by a 1-methyl-6-oxabicyclo[3.2.1]oct-2-ene motif of ring A. Their structures with absolute configurations were unambiguously determined by the extensive spectroscopic methods, X-ray crystallography, and ECD calculation. Putative biosynthetic pathways for compounds 1—3 are proposed. All compounds exhibited antiadipogenic effects in 3T3-L1 adipocytes, and the most potent compound 4 showed an EC₅₀ value of 3.92 μmol/L with low cytotoxicity (IC₅₀ > 89.54 μmol/L).

Two reaction modes for metal-free [3 + 2] cyclization of N-aminopyridinium derivatives with β-alkoxyvinyl trifluoromethylketones have been described through selective C—O or C—O/C—C bond cleavage. This strategy can also be extended to the [3 + 2] cyclization of N-aminopyridinium derivatives with enaminones and bromoalkynes. A broad range of N-aminopyridinium, N-aminoquinolinium, and N-aminoisoquinolinium salts are well tolerated, enabling the divergent synthesis of trifluoroacylated, non-substituted, acylated, and brominated pyrazolo[1,5-a]pyridine derivatives (62 examples).

An efficient asymmetric [4+2] cyclization of hydroxyphenyl indolinone with azlactone for the synthesis of spirooxindole δ-lactone has been developed, which realized the first asymmetric reaction of hydroxyphenyl indolinone. A series of intricate structures with congested vicinal quaternary chiral centers were provided in good yields with excellent enantioselectivities via the in situ generated o-QM from hydroxyphenyl indolinone.

A visible-light-induced decarboxylative radical cascade cyclization reaction between N-(2-cyanoaryl)-acrylamides and alkyl N-(acyloxy)phthalimide (NHPI esters) for the construction of phenanthridine derivatives has been developed. This approach utilizes lithium iodide (LiI) and triphenylphosphine (PPh₃) as the redox catalysts and the alkyl radical is produced through the photoactivation of the electron donor-acceptor (EDA) complex. A series of primary, secondary, and tertiary alkyl-substituted phenanthridines are prepared in up to 82% yield without transition-metal catalysts, chemical oxidants, or metal-/organic dye-based photocatalysts.