Melatonin attenuates intermittent hypoxia-induced cognitive impairment in aged mice: The role of inflammation and synaptic plasticity.

Intermittent hypoxia (IH), a major pathophysiologic alteration in obstructive sleep apnea syndrome (OSAS), is an important contributor to cognitive impairment. Increasing research suggests that melatonin has anti-inflammatory properties and improves functions related to synaptic plasticity. However, it is unclear whether melatonin has a protective effect against OSAS-induced cognitive dysfunction in aged individuals and the involved mechanisms are also unclear. Therefore, in the study, the effects of exposure to IH alone and IH in combination with daily melatonin treatment were investigated in C57BL/6 J mice aged 18 months. Assessment of the cognitive ability of mice in a Morris water maze showed that melatonin attenuated IH-induced impairment of learning and memory in aged mice. Enzyme-linked immunosorbent assay, polymerase chain reaction, and western blotting molecular techniques showed that melatonin treatment reduced the levels of the proinflammatory cytokines, interleukin-1ß, interleukin-6, and tumor necrosis factor-α, decreased the levels of NOD-like receptor thermal protein domain associated protein 3 and nuclear factor kappa-B, lowered the levels of ionized calcium-binding adapter molecule 1 and glial fibrillary acidic protein, and increased the levels of the synaptic proteins, activity-regulated cytoskeleton-associated protein, growth-associated protein-43, postsynaptic density protein 95, and synaptophysin in IH-exposed mice. Moreover, electrophysiological results showed that melatonin ameliorated the decline in long-term potentiation induced by IH. The results suggest that melatonin can ameliorate IH-induced cognitive deficits by inhibiting neuroinflammation and improving synaptic plasticity in aged mice.

Association of hemoglobin glycation index with clinical outcomes in patients with coronary artery disease: a prospective cohort study.

BACKGROUND: To analyze the association between the hemoglobin glycation index (HGI) and the long-term prognosis of patients with coronary artery disease (CAD). METHODS: HGI represented the difference between laboratory measured Hemoglobin A1c (HbA1c) and predicted HbA1c based on a liner regression between Hb1Ac and fasting plasma glucose (FPG). A total of 10 598 patients who treated with percutaneous coronary intervention (PCI) were stratified into three groups (low HGI group: HGI<-0.506, medium HGI group: -0.506 ≤ HGI < 0.179, and high HGI group: HGI ≥ 0.179). The primary endpoints includes all-cause mortality (ACM) and cardiac mortality (CM). The secondary endpoints were major adverse cardiac events (MACEs) and major adverse cardiac and cerebrovascular events (MACCEs). RESULTS: A total of 321 ACMs, 243 CMs, 774 MACEs, and 854 MACCEs were recorded during a 60-month follow-up period. After adjusting for confounders using a multivariate Cox regression analysis, the patients in the low HGI group had a significantly increased risk of ACM (adjusted HR = 1.683, 95%CI:1.179-2.404, P = 0.004) and CM (HR = 1.604, 95%CI:1.064-2.417, P = 0.024) as compared with patients in the medium HGI group. Similarly, the patients in the high HGI group had an increased risk of MACEs (HR = 1.247, 95% CI: 1.023-1.521, P = 0.029) as compared with patients in the medium HGI group. For ACM, CM, and MACEs, a U-shaped relation were found among these three groups. However, we did not find significant differences in the incidence of MACCEs among these three groups. CONCLUSION: The present study indicates that HGI could be an independent predictor for the risk of mortality and MACEs in patients with CAD.

Zinc-Catalyzed Enantioselective Formal (3+2) Cycloadditions of Bicyclobutanes with Imines: Catalytic Asymmetric Synthesis of Azabicyclo[2.1.1]hexanes.

The cycloaddition reaction involving bicyclo[1.1.0]butanes (BCBs) offers a versatile and efficient synthetic platform for producing C(sp3)-rich rigid bridged ring scaffolds, which act as phenyl bioisosteres. However, there is a scarcity of catalytic asymmetric cycloadditions of BCBs to fulfill the need for enantioenriched saturated bicycles in drug design and development. In this study, an efficient synthesis of valuable azabicyclo[2.1.1]hexanes (aza-BCHs) by an enantioselective zinc-catalyzed (3+2) cycloadditions of BCBs with imines is reported. The reaction proceeds effectively with a novel type of BCB that incorporates a 2-acyl imidazole group and a diverse array of alkynyl- and aryl-substituted imines. The target aza-BCHs, which consist of α-chiral amine fragments and two quaternary carbon centers, are efficiently synthesized with up to 94% yield and 96.5:3.5 er under mild conditions. Experimental and computational studies reveal that the reaction follows a concerted nucleophilic ring-opening mechanism of BCBs with imines. This mechanism is distinct from previous studies on Lewis acid-catalyzed cycloadditions of BCBs.

Effects of T2DM on cancer progression: pivotal precipitating factors and underlying mechanisms.

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder affecting people worldwide. It is characterized by several key features, including hyperinsulinemia, hyperglycemia, hyperlipidemia, and dysbiosis. Epidemiologic studies have shown that T2DM is closely associated with the development and progression of cancer. T2DM-related hyperinsulinemia, hyperglycemia, and hyperlipidemia contribute to cancer progression through complex signaling pathways. These factors increase drug resistance, apoptosis resistance, and the migration, invasion, and proliferation of cancer cells. Here, we will focus on the role of hyperinsulinemia, hyperglycemia, and hyperlipidemia associated with T2DM in cancer development. Additionally, we will elucidate the potential molecular mechanisms underlying their effects on cancer progression. We aim to identify potential therapeutic targets for T2DM-related malignancies and explore relevant directions for future investigation.

Protein-protein interactions in cGAS-STING pathway: a medicinal chemistry perspective.

Protein-protein interactions (PPIs) play pivotal roles in biological processes and are closely linked with human diseases. Research on small molecule inhibitors targeting PPIs provides valuable insights and guidance for novel drug development. The cGAS-STING pathway plays a crucial role in regulating human innate immunity and is implicated in various pathological conditions. Therefore, modulators of the cGAS-STING pathway have garnered extensive attention. Given that this pathway involves multiple PPIs, modulating PPIs associated with the cGAS-STING pathway has emerged as a promising strategy for modulating this pathway. In this review, we summarize an overview of recent advancements in medicinal chemistry insights into cGAS-STING PPI-based modulators and propose alternative strategies for further drug discovery based on the cGAS-STING pathway.

[Box: see text].

The Genome-Wide Identification of the Dihydroflavonol 4-Reductase (DFR) Gene Family and Its Expression Analysis in Different Fruit Coloring Stages of Strawberry.

Dihydroflavonol 4-reductase (DFR) significantly influences the modification of flower color. To explore the role of DFR in the synthesis of strawberry anthocyanins, in this study, we downloaded the CDS sequences of the DFR gene family from the Arabidopsis genome database TAIR; the DFR family of forest strawberry was compared; then, a functional domain screen was performed using NCBI; the selected strawberry DFR genes were analyzed; and the expression characteristics of the family members were studied by qRT-PCR. The results showed that there are 57 members of the DFR gene family in strawberry, which are mainly expressed in the cytoplasm and chloroplast; most of them are hydrophilic proteins; and the secondary structure of the protein is mainly composed of α-helices and random coils. The analysis revealed that FvDFR genes mostly contain light, hormone, abiotic stress, and meristem response elements. From the results of the qRT-PCR analysis, the relative expression of each member of the FvDFR gene was significantly different, which was expressed throughout the process of fruit coloring. Most genes had the highest expression levels in the full coloring stage (S4). The expression of FvDFR30, FvDFR54, and FvDFR56 during the S4 period was 8, 2.4, and 2.4 times higher than during the S1 period, indicating that the DFR gene plays a key role in regulating the fruit coloration of strawberry. In the strawberry genome, 57 members of the strawberry DFR gene family were identified. The higher the DFR gene expression, the higher the anthocyanin content, and the DFR gene may be the key gene in anthocyanin synthesis. Collectively, the DFR gene is closely related to fruit coloring, which lays a foundation for further exploring the function of the DFR gene family.

Enantioselective formal (3 + 3) cycloaddition of bicyclobutanes with nitrones enabled by asymmetric Lewis acid catalysis.

The absence of catalytic asymmetric methods for synthesizing chiral (hetero)bicyclo[n.1.1]alkanes has hindered their application in new drug discovery. Here we demonstrate the achievability of an asymmetric polar cycloaddition of bicyclo[1.1.0]butane using a chiral Lewis acid catalyst and a bidentate chelating bicyclo[1.1.0]butane substrate, as exemplified by the current enantioselective formal (3 + 3) cycloaddition of bicyclo[1.1.0]butanes with nitrones. In addition to the diverse bicyclo[1.1.0]butanes incorporating an acyl imidazole group or an acyl pyrazole moiety, a wide array of nitrones are compatible with this Lewis acid catalysis, successfully assembling two congested quaternary carbon centers and a chiral aza-trisubstituted carbon center in the pharmaceutically important hetero-bicyclo[3.1.1]heptane product with up to 99% yield and >99% ee.

Association between Paraspinal Muscle Parameters and single-segment Degenerative Lumbar Spondylolisthesis: A Retrospective, cross-sectional Cohort Study.

STUDY DESIGN: A retrospective, cross-sectional cohort study. OBJECTIVE: This study aims to investigate the association between paraspinal muscle parameters and single-segment degenerative lumbar spondylolisthesis (DLS). SUMMARY OF BACKGROUND DATA: The relationship between lumbar paraspinal muscles morphology and single-segment DLS remains unclear. METHODS: A retrospective review was conducted on 115 patients with L4/5 single-segment DLS and 105 subjects without DLS. Two independent investigators assessed the relative cross-sectional area and fat infiltration rate of the multifidus, erector spinae, and psoas major at L3/4, L4/5, and L5/S1 levels, comparing these measurements between the two groups. Additionally, binary logistic regression analysis was performed with DLS as the dependent variable to analyze the relative cross-sectional area and fat infiltration rate of different paraspinal muscles. Within the DLS group, the correlation between paraspinal muscle characteristics and the anteroposterior diameter of the spinal canal was examined. RESULTS: The fat infiltration rate of multifidus, erector spinae, and psoas major were higher in the DLS group than in the control group, while the relative cross-sectional area of multifidus and psoas major were lower in the DLS group. Binary logistic regression analysis revealed a significant correlation between fat infiltration rate of multifidus and psoas major and DLS. The relative cross-sectional area of multifidus and erector spinae was significantly smaller below the affected segment in the DLS group compared to the control group. A significant positive correlation was observed between the relative cross-sectional area of multifidus and erector spinae and the anteroposterior diameter of the spinal canal. CONCLUSION: There is a close association between paraspinal muscle degeneration and single-segment DLS, with increased relative cross-sectional area of the multifidus and psoas major possibly being risk factors for single-segment DLS. The restoration or enhancement of paraspinal muscle function could potentially serve as a pivotal target for the prevention and treatment of single-segment DLS. LEVEL OF EVIDENCE: III.

Structurally diverse ent-clerodanoids from the aerial parts of Isodon scoparius.

Scoparodane C (1), a diterpenoid with a rare 3,4-seco-3-nor-2,11-epoxy-ent-clerodane scaffold, was obtained from the aerial parts of Isodon scoparius, along with isocopariusines A-E (2-6), five ent-clerodanoids featuring a 5/6-fused ring system, and isocopariusines F-H (7-9), three common ent-clerodanoids. The structures of these previously undescribed compounds were established by a combination of spectroscopic analysis, X-ray diffraction, chemical derivatization, and quantum chemical calculation. Remarkably, isocopariusine B (3) showed strong resistance reversal activity against fluconazole-resistant Candida albicans.

TaMYB-CC5 gene specifically expressed in root improve tolerance of phosphorus deficiency and drought stress in wheat.

Phosphate deficiency and drought are significant environmental constraints that impact both the productivity and quality of wheat. The interaction between phosphorus and water facilitates their mutual absorption processes in plants. Under conditions of both phosphorus deficiency and drought stress, we observed a significant upregulation in the expression of wheat MYB-CC transcription factors through the transcriptome analysis. 52 TaMYB-CC genes in wheat were identified and analyzed their evolutionary relationships, structures, and expression patterns. The TaMYB-CC5 gene exhibited specific expression in roots and demonstrated significant upregulation under phosphorus deficiency and drought stress compared to other TaMYB-CC genes. The overexpression of TaMYB-CC5A in Arabidopsis resulted in a significant increase of root length under stress conditions, thereby enhancing tolerance to phosphate starvation and drought stress. The wheat lines with silenced TaMYB-CC5 genes exhibited reduced root length under stress conditions and increased sensitivity to phosphate deficiency and drought stress. In addition, silencing the TaMYB-CC5 genes resulted in altered phosphorus content in leaves but did not lead to a reduction in phosphorus content in roots. Enrichment analysis the co-expression genes of TaMYB-CC5 transcription factors, we found the zinc-induced facilitator-like (ZIFL) genes were prominent associated with TaMYB-CC5 gene. The TaZIFL1, TaZIFL2, and TaZIFL5 genes were verified specifically expressed in roots and regulated by TaMYB-CC5 transcript factor. Our study reveals the pivotal role of the TaMYB-CC5 gene in regulating TaZIFL genes, which is crucial for maintaining normal root growth under phosphorus deficiency and drought stress, thereby enhanced resistance to these abiotic stresses in wheat.

Lathyrane diterpenoids with multidrug resistance reversal activity from the tubers of Euphorbia antiquorum.

Nine previously unreported lathyrane diterpenoids named euphorantesters A-I, along with 16 known analogues, have been separated from the tubers of Euphorbia antiquorum. Their structures were established by means of spectroscopic analyses, time-dependent density functional theory based electronic circular dichroism calculation and single crystal X-ray crystallography. Their reversal ability against P-glycoprotein-mediated multidrug resistance (MDR) in MCF-7/ADR cell line was then evaluated, and 15 ones exhibited moderate MDR reversal activity with reversal fold falling in the range of 1.12-13.15. The most active euphorantester B could effectively increase the sensitivity of MCF-7/ADR cell to adriamycin comparably to the reference drug verapamil.

Association of redundant foreskin with sexual dysfunction: a cross-sectional study from 5700 participants.

A previous study showed that the length of the foreskin plays a role in the risk of sexually transmitted infections and chronic prostatitis, which can lead to poor quality of sexual life. Here, the association between foreskin length and sexual dysfunction was evaluated. A total of 5700 participants were recruited from the andrology clinic at The First Affiliated Hospital of University of Science and Technology of China (Hefei, China). Clinical characteristics, including foreskin length, were collected, and sexual function was assessed by the International Index of Erectile Function-5 (IIEF-5) and Premature Ejaculation Diagnostic Tool (PEDT) questionnaires. Men with sexual dysfunction were more likely to have redundant foreskin than men without sexual dysfunction. Among the 2721 erectile dysfunction (ED) patients and 1064 premature ejaculation (PE) patients, 301 (11.1%) ED patients and 135 (12.7%) PE patients had redundant foreskin, respectively. Men in the PE group were more likely to have redundant foreskin than men in the non-PE group (P = 0.004). Logistic regression analyses revealed that the presence of redundant foreskin was associated with increased odds of moderate/severe ED (adjusted odds ratio [aOR] = 1.31, adjusted P = 0.04), moderate PE (aOR = 1.38, adjusted P = 0.02), and probable PE (aOR = 1.37, adjusted P = 0.03) after adjusting for confounding variables. Our study revealed a positive correlation between the presence of redundant foreskin and the risk of sexual dysfunction, especially in PE patients. Assessment of the length of the foreskin during routine clinical diagnosis may provide information for patients with sexual dysfunction.

[Ecological Transition from Micro-remediation to Ecological Regulation of Petroleum Pollution].

Petroleum pollution has become a prominent global environmental problem, restricting the coordinated development of the economy and the ecological environment. Although bioremediation has the advantages of low carbon, high efficiency, and safety, the complexity and severity of the pollution makes it difficult to achieve the remediation purpose with a single bioremediation. Ecological remediation based on bioremediation can integrate carbon neutrality and ecological environmental protection, synergistically promote pollution reduction and carbon reduction, ensure the sustainability of soil and sediment to fulfil ecosystem service functions, and ultimately achieve soil health and sediment health. Therefore, the transition from bioremediation to ecological restoration is the optimal choice for environmental management and ecosystem maintenance at this stage. Here, we first analyzed the micro-removal mechanism of petroleum hydrocarbons in different bioremediation techniques and discussed the types and characteristics of different bioremediation techniques from an ecological point of view. Based on this, the necessity of bioremediation for ecological restoration was analyzed in detail. Finally, a reasonable outlook on the development of ecological remediation is given to provide theoretical support for optimizing ecological remediation of petroleum pollution.

CircUGP2 Suppresses Intrahepatic Cholangiocarcinoma Progression via p53 Signaling Through Interacting With PURB to Regulate ADGRB1 Transcription and Sponging miR-3191-5p.

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver cancer and its prognosis remains poor. Although growing numbers of studies have verified the involvement of circular RNAs (circRNAs) in various cancer types, their specific functions in ICC remain elusive. Herein, a circRNA, circUGP2 is identified by circRNA sequencing, which is downregulated in ICC tissues and correlated with patients' prognosis. Moreover, circUGP2 overexpression suppresses tumor progression in vitro and in vivo. Mechanistically, circUGP2 functions as a transcriptional co-activator of PURB over the expression of ADGRB1. It can also upregulate ADGRB1 expression by sponging miR-3191-5p. As a result, ADGRB1 prevents MDM2-mediated p53 polyubiquitination and thereby activates p53 signaling to inhibit ICC progression. Based on these findings, circUGP2 plasmid is encapsulated into a lipid nanoparticle (LNP) system, which has successfully targeted tumor site and shows superior anti-tumor effects. In summary, the present study has identified the role of circUGP2 as a tumor suppressor in ICC through regulating ADGRB1/p53 axis, and the application of LNP provides a promising translational strategy for ICC treatment.

Improved Patient Adherence to Family-Based Helicobacter pylori Infection Control and Management Strategy in Central China and Its Influencing Factors.

BACKGROUND: Patient adherence status to the newly introduced family-based Helicobacter pylori (H. pylori) infection control and management strategy remains unclear, so are its influencing factors. We aim to investigate family members' adherence and its influencing factors during the family-based H. pylori infection management practice for related disease prevention. MATERIALS AND METHODS: Based on our previously family-based H. pylori survey in 2021, 282 families including 772 individuals were followed up 2 years after the initial survey to compare if the investigation and education might improve family member's adherence. The participant's adherence to H. pylori infection awareness, retest, treatment, publicity, gastroscopy, and hygiene habits were followed up, and their influencing factors were also analyzed. RESULTS: The overall participant's adherence to recommendations on H. pylori awareness, retest, treatment, publicity, gastroscopy, and hygiene habits were 77% (187/243), 67.3% (138/205), 60.1% (211/351), 46.5% (107/230), 45.6% (159/349), and 39.1% (213/545), respectively; and all showed improvements compared with their prior survey stages. The top reasons for rejection to treatment, retest, and gastroscopy were forgetting or unaware of H. pylori infection (30.3%), busy (32.8%), and asymptomatic (67.9%), respectively. Independent risk factor for low adherence to treatment was occupation (e.g., staff: OR 4.49, 95% CI 1.34-15.10). Independent favorable factors for treatment adherence were individuals at the ages of 18-44 years (OR 0.19, 95% CI 0.04-0.89) and had a large family size (e.g., four family members: OR 0.15, 95% CI 0.06-0.41); for retest adherence, it was individuals at the ages of 60-69 years (OR 0.23, 95% CI 0.06-0.97); for gastroscopy adherence, it was individuals at the age of 60-69 years (OR 0.46, 95% CI 0.28-0.75), and with gastrointestinal symptoms (OR 0.57, 95% CI 0.36-0.90). CONCLUSIONS: Family-based H. pylori management increases individual adherence to treatment, retest, and awareness, and there are also improved adherence to gastroscopy, publicity, and personal hygiene recommendations; further efforts are required to enhance the individual adherence rate for related disease prevention.

Risk factors associated with intraoperative persistent hypotension in pancreaticoduodenectomy.

BACKGROUND: Intraoperative persistent hypotension (IPH) during pancreaticoduodenectomy (PD) is linked to adverse postoperative outcomes, yet its risk factors remain unclear. AIM: To clarify the risk factors associated with IPH during PD, ensuring patient safety in the perioperative period. METHODS: A retrospective analysis of patient records from January 2018 to December 2022 at the First Affiliated Hospital of Nanjing Medical University identified factors associated with IPH in PD. These factors included age, gender, body mass index, American Society of Anesthesiologists classification, comorbidities, medication history, operation duration, fluid balance, blood loss, urine output, and blood gas parameters. IPH was defined as sustained mean arterial pressure < 65 mmHg, requiring prolonged deoxyepinephrine infusion for > 30 min despite additional deoxyepinephrine and fluid treatments. RESULTS: Among 1596 PD patients, 661 (41.42%) experienced IPH. Multivariate logistic regression identified key risk factors: increased age [odds ratio (OR): 1.20 per decade, 95% confidence interval (CI): 1.08-1.33] (P < 0.001), longer surgery duration (OR: 1.15 per additional hour, 95%CI: 1.05-1.26) (P < 0.01), and greater blood loss (OR: 1.18 per 250-mL increment, 95%CI: 1.06-1.32) (P < 0.01). A novel finding was the association of arterial blood Ca2+ < 1.05 mmol/L with IPH (OR: 2.03, 95%CI: 1.65-2.50) (P < 0.001). CONCLUSION: IPH during PD is independently associated with older age, prolonged surgery, increased blood loss, and lower plasma Ca2+.

Advanced Strategies for Strengthening the Immune Activation Effect of Traditional Antitumor Therapies.

The utilization of traditional therapies (TTS), such as chemotherapy, reactive oxygen species-based therapy, and thermotherapy, to induce immunogenic cell death (ICD) in tumor cells has emerged as a promising strategy for the activation of the antitumor immune response. However, the limited effectiveness of most TTS in inducing the ICD effect of tumors hinders their applications in combination with immunotherapy. To address this challenge, various intelligent strategies have been proposed to strengthen the immune activation effect of these TTS, and then achieve synergistic antitumor efficacy with immunotherapy. These strategies primarily focus on augmenting the tumor ICD effect or facilitating the antigen (released by the ICD tumor cells) presentation process during TTS, and they are systematically summarized in this review. Finally, the existing bottlenecks and prospects of TTS in the application of tumor immune regulation are also discussed.

An updated patent review of stimulator of interferon genes agonists (2021 - present).

INTRODUCTION: Stimulator of Interferon Genes (STING) is an innate immune sensor. Activation of STING triggers a downstream response that results in the expression of proinflammatory cytokines (TNF-α, IL-1ß) via nuclear factor kappa-B (NF-κB) or the expression of type I interferons (IFNs) via an interferon regulatory factor 3 (IRF3). IFNs can eventually result in promotion of the adaptive immune response including activation of tumor-specific CD8+ T cells to abolish the tumor. Consequently, activation of STING has been considered as a potential strategy for cancer treatment. AREAS COVERED: This article provides an overview on structures and pharmacological data of CDN-like and non-nucleotide STING agonists acting as anticancer agents (January 2021 to October 2023) from a medicinal chemistry perspective. The data in this review come from EPO, WIPO, RCSB PDB, CDDI. EXPERT OPINION: In recent years, several structurally diverse STING agonists have been identified. As an immune enhancer, they are used in the treatment of tumors, which has received extensive attention from scientific community and pharmaceutical companies. Despite the multiple challenges that have appeared, STING agonists may offer opportunities for immunotherapy.

Triterpenoids with α-glucosidase inhibitory and cytotoxic activities from the fruits of Schisandra chinensis.

An intensive phytochemical investigation into the fruits of Schisandra chinensis afforded 28 triterpenoids incorporating diverse backbones with methyl-migration, ring-expansion and ring-opening features. Among them, ten compounds (1-10) including three likely extracting artefacts (8-10) were described for the first time. Their structures were fully characterized by comprehensive spectroscopic analyses, with the absolute configurations established via electronic circular dichroism and Mosher's NMR techniques. Preliminary biological evaluations revealed that nine isolates showed inhibitory activity against the hyperglycemic target α-glycosidase and 12 compounds exerted cytotoxicity toward three female tumor cell lines (Hela (cervical), MDA-MB231 and MCF-7 (breast)). Compound 6 exhibited the most promising potency on all the three tested cancer cells, and further assessment demonstrated that it could induce significant cell apoptosis and cycle arrest, as well as suppress cell migration, by regulating relevant proteins in MDA-MB231 cells.

Palladium-Catalyzed Ligand-Controlled Switchable Hetero-(5 + 3)/Enantioselective [2σ+2σ] Cycloadditions of Bicyclobutanes with Vinyl Oxiranes.

For nearly 60 years, significant research efforts have been focused on developing strategies for the cycloaddition of bicyclobutanes (BCBs). However, higher-order cycloaddition and catalytic asymmetric cycloaddition of BCBs have been long-standing formidable challenges. Here, we report Pd-catalyzed ligand-controlled, tunable cycloadditions for the divergent synthesis of bridged bicyclic frameworks. The dppb ligand facilitates the formal (5+3) cycloaddition of BCBs and vinyl oxiranes, yielding valuable eight-membered ethers with bridged bicyclic scaffolds in 100% regioselectivity. The Cy-DPEphos ligand promotes selective hetero-[2σ+2σ] cycloadditions to access pharmacologically important 2-oxabicyclo[3.1.1]heptane (O-BCHeps). Furthermore, the corresponding catalytic asymmetric synthesis of O-BCHeps with 94-99% ee has been achieved using chiral (S)-DTBM-Segphos, representing the first catalytic asymmetric cross-dimerization of two strained rings. The obtained O-BCHeps are promising bioisosteres for ortho-substituted benzenes.