Organic Photoredox-Catalyzed Hydrosilylation of Vinylboronic Esters for the Synthesis of Geminal and Vicinal Borosilanes.

Geminal and vicinal borosilanes have unique applications in functional materials and synthetic transformations. Herein, a convenient method for the synthesis of geminal and vicinal borosilanes is developed via photoredox metal-free hydrosilylation of vinylboronic esters. This strategy features the advantages of high atom economy, environmental friendliness, and excellent functional group compatibility. The mechanism studies reveal that the catalytic reaction goes through photoredox HAT catalysis and a radical addition pathway.

Ampelopsis grossedentata Represents a New Host of the 16SrI Group of Phytoplasma Associated with Yellow Leaf Symptoms in China.

Ampelopsis grossedentata, commonly known as "Vine Tea" and well-recognized for its rich flavonoid content, is mainly distributed in the southern regions of the Yangtze River basin in China. These regions include Hunan, Hubei, Jiangxi, and Guizhou provinces. Vine Tea is mainly consumed as an herbal tea and has garnered attention for its reported health benefits, including antioxidant, anti-inflammatory, anti-tumor, anti-diabetic, and neuroprotective properties. It has been used to alleviate coughs and sore throats (Zhang et al., 2021; Wang et al., 2017; Gao et al., 2009). In the Zhangjiajie region of Hunan province alone, the Vine Tea planting area reached 7,670.5 hectares and produced commercial goods worth 1.417 billion RMB in 2022. In May 2021, leaf margins and veins fading to yellowing mottling, and crumpling of leaf blades in the shape of a boat symptoms were found in ~16% of Vine Tea plants in the Sanjiakuan Township, Yongding District, Zhangjiajie region (29°15'E, 110°30' N) (Figure 1a, b, c). (Figure 1a, b, c). Phytoplasma-like microbial cells (small oval shaped bacterial cells, around 1000 nm in size) were observed in sieve tube cells in the phloem of diseased leaves using transmission electron microscopy. No such cell was observed in the phloem of healthy leaves (Figure 2a, b). To investigate the potential association between phytoplasma and the observed symptoms of the diseased plants, total DNA was isolated from ten diseasedeaves and compared with ten healthy leaves from the same field using SteadyPure Plant Genomic DNA Extraction Kit. The isolated DNAs were analyzed first in a direct PCR using universal phytoplasma primer pair R16mF2/R16mR1 targeting the 16S rRNA gene (Gundersen and Lee 1996) and specific pair rpF1/rpR1 (Lee et al. 1998) targeting the DNA fragment encoding partial ribosomal proteins (rp) L22 (complete) and S3 and S19 (partial). The initial amplified products were used as templates and further amplified by nested PCR respectively with primer pair R16F2n/R16R2 for the 16S rRNA gene (Lee et al. 1998) and the rpF2/rpR2 primer pair for the rp gene (Martini et al. 2007). No amplification was obtained with DNA from healthy leaf samples using any of the four primer pairs. The amplified fragments from diseased leaves by nested PCR were cloned and sequenced (Qingke Biotech, China). The obtained sequences have been deposited in GenBank with accession numbers OR282806 for the 16S rRNA gene and GenBank OR353012 for the rp gene. BLASTn analysis revealed that the partial 16S rRNA gene sequence in our sample shared 99.4% nucleotide sequence identity with 'Candidatus Phytoplasma sp.' (MW364378) and 'Peony yellows phytoplasma' (KY814723) of the 16SrI group. Similarly, our rp gene sequence shared 99.6% nucleotide identity with the rpI group of phytoplasma such as the 'Balsamine virescence phytoplasma' (JN572890) and 'Paulownia witches'-broom phytoplasma' (HM146079). Phylogenetic analysis of the 16S rRNA and rp sequences using MEGA version 7.0 revealed that the phytoplasma strain associated with A. grossedentata yellow leaf syndrome in our study site belonged to the 16SrI (Candidatus Phytoplasma asteris) group of phytoplasma (Figure 3a, b). Using the interactive online phytoplasma classification tool iPhyClassifier (Zhao et al., 2009), virtual restriction fragment length polymorphism (RFLP) analysis of the 16S rRNA gene sequences showed our strain having a distinct RFLP map but was closest to that of the onion yellow phytoplasma 16SrI-B subgroup (GenBank accession number: AP006628), with a similarity coefficient of 0.94 (Figure 4a, b). To confirm phytoplasma transmission, healthy plants were inoculated with three scions of infected plants of A. grossedentata. After 16 days, the new leaves of the inoculated A. grossedentata showed yellow leaf symptoms (Figure 5a, b, c), akin to the symptoms originally observed in the field, and the outer contour of the leaf margin appeared chlorotic. After 26 days, primer pairs R16mF2/R16R1 and R16F2n/R16R2 were used for nested PCR detection of phytoplasma in symptomatic A. grossedentata leaves. Phytoplasma was detected in the first and second leaves of symptomatic branches and leaves while negative control showed no amplification. Sequencing of the amplified fragments showed 100% nucleotide identity to the strain from the grafting source. Our results indicated that the pathogen and the disease can be transmitted by tissue grafting, consistent with the biological characteristics of phytoplasma, and further confirmed that the phytoplasma was the pathogen of yellow leaf syndrome of A. grossedentata. Toour knowledge, this is the first report of phytoplasma of group 16SrI affecting A. grossedentata.

Photocatalytic Synthesis of Diarylmethyl Silanes via 1,6-Conjugate Addition of Silyl Radicals to p-Quinone Methides.

A novel photocatalytic method for the preparation of diarylmethyl silanes was reported through silyl radicals addition strategy to p-QMs (p-quinone methides). This protocol could tolerate a variety of functional groups affording the corresponding silylation products with moderate to excellent yields. The resulting silylation products could be easily converted into a series of bioactive GPR40 agonists and useful p-QMs precursors for the synthesis of compounds possessing both quaternary carbon centers and silicon substituents through simple operation. A plausible mechanism of silyl radicals to p-QMs was proposed on the basis of experimental results and previous literature.

First Report of Diaporthe hongkongensis Causing Fruit rot on Peach (Prunus persica) in China.

Peach [Prunus persica (L.) Batsch] is an important deciduous fruit tree in the family Rosaceae and is a widely grown fruit in China (Verde et al., 2013). In July and August 2018, a fruit rot disease was observed in a few peach orchards in Zhuzhou city, the Hunan Province of China. Approximately 30% of the fruit in more than 400 trees was affected. Symptoms displayed were brown necrotic spots that expanded, coalesced, and lead to fruit being rotten. Symptomatic tissues excised from the margins of lesions were surface sterilized in 70% ethanol for 10 s, 0.1% HgCl2 for 2 min, rinsed with sterile distilled water three times, and incubated on potato dextrose agar (PDA) at 26°C in the dark. Fungal colonies with similar morphology developed, and eight fungal colonies were isolated for further identification. Colonies grown on PDA were grayish-white with white aerial mycelium. After an incubation period of approximately 3 weeks, pycnidia developed and produced α-conidia and ß-conidia. The α-conidia were one-celled, hyaline, fusiform, and ranged in size from 6.0 to 8.4 × 2.1 to 3.1 µm, whereas the ß-conidia were filiform, hamate, and 15.0 to 27.0 × 0.8 to 1.6 µm. For molecular identification, total genomic DNA was extracted from the mycelium of a representative isolate HT-1 and the internal transcribed spacer region (ITS), ß-tubulin gene (TUB), translation elongation factor 1-α gene (TEF1), calmodulin (CAL), and histone H3 gene (HIS) were amplified and sequenced (Meng et al. 2018). The ITS, TUB, TEF1, CAL and HIS sequences (GenBank accession nos. MT740484, MT749776, MT749778, MT749777, and MT749779, respectively) were obtained and in analysis by BLAST against sequences in NCBI GenBank, showed 99.37 to 100% identity with D. hongkongensis or D. lithocarpus (the synonym of D. hongkongensis) (Gao et al., 2016) (GenBank accession nos. MG832540.1 for ITS, LT601561.1 for TUB, KJ490551.1 for HIS, KY433566.1 for TEF1, and MK442962.1 for CAL). Pathogenicity tests were performed on peach fruits by inoculation of mycelial plugs and conidial suspensions. In one set, 0.5 mm diameter mycelial discs, which were obtained from an actively growing representative isolate of the fungus on PDA, were placed individually on the surface of each fruit. Sterile agar plugs were used as controls. In another set, each of the fruits was inoculated by application of 1 ml conidial suspension (105 conidia/ml) by a spray bottle. Control assays were carried out with sterile distilled water. All treatments were maintained in humid chambers at 26°C with a 12-h photoperiod. The inoculation tests were conducted twice, with each one having three fruits as replications. Six days post-inoculation, symptoms of fruit rot were observed on inoculated fruits, whereas no symptoms developed on fruits treated with agar plugs and sterile water. The fungus was re-isolated and identified to be D. hongkongensis by morphological and molecular methods, thus fulfilling Koch's Postulates. This fungus has been reported to cause fruit rot on kiwifruit (Li et al. 2016) and is also known to cause peach tree dieback in China (Dissanayake et al. 2017). However, to our knowledge, this is the first report of D. hongkongensis causing peach fruit rot disease in China. The identification of the pathogen will provide important information for growers to manage this disease.

Organocatalytic Enantioselective Michael/Cyclization Domino Reaction between 3-Amideoxindoles and α,ß-Unsaturated Aldehydes: One-Pot Preparation of Chiral Spirocyclic Oxindole-γ-lactams.

The first organocatalytic enantioselective Michael/cyclization domino reaction between 3-amideoxindoles and α,ß-unsaturated aldehydes is described. After sequential oxidation with pyridinium chlorochromate, a direct and one-pot preparation of highly sterically hindered spirocyclic oxindole-γ-lactams was achieved in 51-81% yields with 75-97% ee and ≤80/20 dr.

An efficient and enantioselective Michael addition of aromatic oximes to α,ß-unsaturated aldehydes promoted by a chiral diamine catalyst derived from α,α-diphenyl prolinol.

Chiral diamine catalysts 11a-e derived from α,α-diphenyl prolinol were prepared and successfully applied to the Michael addition of aromatic oximes to α,ß-unsaturated aldehydes in mediocre to good yields (up to 78%) and good to high enantioselectivities (up to 93% ee).

Silylation and (Hetero)aryl/alkenylation of Unactivated Alkenes via Radical-Mediated Distal 1,4-Migration with Hydrosilanes under Organophotocatalysis.

We report a novel organic photoredox catalysis to achieve unprecedented γ-(hetero)aryl/alkenyl-δ-silyl aliphatic amines via silyl-mediated distal (hetero)aryl/alkenyl migration of aromatic/alkenyl amines bearing unactivated alkenes with hydrosilanes. This protocol features mild and metal-free reaction conditions, high atom economy, excellent selectivity, and functional group compatibility. Mechanistic studies suggest that silylation and (hetero)aryl/alkenylation involve photoredox hydrogen atom transfer catalysis and subsequent 1,4-migration of a remote (hetero)aryl/alkenyl group from nitrogen to carbon.

Photoredox Metal-Free Allylic Defluorinative Silylation of α-Trifluoromethylstyrenes with Hydrosilanes.

We report an efficient strategy that combines organic photoredox and hydrogen atom transfer to deliver gem-difluoroallylsilanes via defluorinative silylation of α-trifluoromethylstyrenes using hydrosilanes as silicon sources. This protocol provides an environmentally friendly approach for the preparation of structurally diverse gem-difluoroallylsilanes with excellent functional group compatibility and renders it suitable for late-stage modification of bioactive and complex molecules.

NHC-Nickel Catalyzed C-N Bond Cleavage of Mono-protected Anilines for C-C Cross-Coupling.

A Ni-catalyzed aryl C-N bond cleavage of mono-protected anilines, N-arylsulfonamides, has been developed. A new N-heterocyclic carbene derived from benzoimidazole shows high reactivity for the C-N cleavage/C-C cross-coupling reaction. The ortho-directing group is not required to break the C-N bond of sulfonyl-protected anilines, which are not limited to π-extended anilines. The mechanistic studies have revealed that a sulfamidomagnesium salt is the key coupling intermediate.

Nickel-Catalyzed Kumada Coupling of Boc-Activated Aromatic Amines via Nondirected Selective Aryl C-N Bond Cleavage.

A nickel-catalyzed Kumada coupling of aniline derivatives was developed by selective cleavage of aryl C-N bonds under mild reaction conditions. Without preinstallation of an ortho directing group on anilines, the cross-coupling reactions of Boc-protected aromatic amines with aryl Grignard reagents afforded unsymmetric biaryls. Mechanistic studies by DFT calculations revealed that the nickel-mediated C-N bond cleavage is the rate-limiting step.

Organocatalytic Asymmetric Annulation between Hydroxymaleimides and Nitrosoarenes: Stereoselective Preparation of Chiral Quaternary N-Hydroxyindolines.

An unusual and highly effective asymmetric annulation of nitrosoarenes with hydroxymaleimides catalyzed by a chiral bifunctional amine squaramide catalyst has been disclosed. A wide range of highly fused chiral N-hydroxyindolines with two consecutive quaternary stereocenters and multifunctional groups were directly and effectively prepared in excellent yields (up to >99%) with complete regioselective cyclization and excellent stereoselectivities (up to >99:1 dr and >99% ee). The efficiency and potentials of the new reaction and the target chiral entities were well demonstrated by delicate transformations into a series of new chiral indolines.

Expression and function of GSTA1 in lung cancer cells.

Glutathione S-transferase A1 (GSTA1) appears to be primarily involved in detoxification processes, but possible roles in lung cancer remain unclear. The objective of this study was to investigate the expression and function of GSTA1 in lung cancer cells. Real-time PCR and Western blotting were performed to assess expression in cancer cell lines and the normal lung cells, then verify the A549 cells line with stable overexpression. Localization of GSTA1 proteins was assessed by cytoimmunofluorescence. Three double-strand DNA oligoRNAs (SiRNAs) were synthesized prior to being transfected into A549 cells with Lipofectamine 2000, and then the most efficient SiRNA was selected. Expression of the GSTA1 gene in the transfected cells was determined by real-time PCR and Western blotting. The viability of the transfected cells were assessed by MTT. Results showed that the mRNA and protein expression of A549 cancer cells was higher than in MRC-5 normal cells. Cytoimmunofluorescence demonstrated GSTA1 localization in the cell cytoplasm and/or membranes. Transfection into A549 cells demonstrated that down-regulated expression could inhibit cell viability. Our data indicated that GSTA1 expression may be a target molecule in early diagnosis and treatment of lung cancer.