Enantioselective Transformations by "1 + x" Synergistic Catalysis with Chiral Primary Amines.

ConspectusSynergistic catalysis is a powerful tool that involves two or more distinctive catalytic systems to activate reaction partners simultaneously, thereby expanding the reactivity space of individual catalysis. As an established catalytic strategy, organocatalysis has found numerous applications in enantioselective transformations under rather mild conditions. Recently, the introduction of other catalytic systems has significantly expanded the reaction space of typical organocatalysis. In this regard, aminocatalysis is a prototypical example of synergistic catalysis. The combination of aminocatalyst and transition metal could be traced back to the early days of organocatalysis and has now been well explored as an enabling catalytic strategy. Particularly, the acid-base properties of aminocatalysis can be significantly expanded to include usually electrophiles generated in situ via metal-catalyzed cycles. Later on, aminocatalyst has also been exploited in synergistically combining with photochemical and electrochemical processes to facilitate redox transformations. However, synergistically combining one type of aminocatalyst with many different catalytic systems remains a great challenge. One of the most daunting challenges is the compatibility of aminocatalysts in coexistence with other catalytic species. As nucleophilic species, aminocatalysts may also bind with metal, which leads to mutual inhibition or even quenching of the individual catalytic activity. In addition, oxidative stability of aminocatalyst is also a non-neglectable issue, which causes difficulties in exploring oxidative enamine transformations.In 2007, we developed a vicinal diamine type of chiral primary aminocatalysts. This class of primary aminocatalysts was developed and evolved as functional and mechanistic mimics to the natural aldolase and has been widely applied in a number of enamine/iminium ion-based transformations. By following a "1 + x" synergistic strategy, the chiral primary amine catalysts were found to work synergistically or cooperatively with a number of transition metal catalysts, such as Pd, Rh, Ag, Co, and Cu, or other organocatalysts, such as B(C6F5)3, ketone, selenium, and iodide. Photocatalysis and electrochemical processes can also be incorporated to work together with the chiral primary amine catalysts. The 1 + x catalytic strategy enabled us to execute unexploited transformations by fine-tuning the acid-base and redox properties of the enamine intermediates and to achieve effective reaction and stereocontrol beyond the reach individually. During these efforts, an unprecedented excited-state chemistry of enamine was uncovered to make possible an effective deracemization process. In this Account, we describe our recent efforts since 2015 in exploring synergistic chiral primary amine catalysis, and the content is categorized according to the type of synergistic partner such that in each section the developed synergistic catalysis, reaction scopes, and mechanistic features are presented and discussed.

ZBP1-mediated apoptosis and inflammation exacerbate steatotic liver ischemia-reperfusion injury.

There is increasing need to expand availability of donor liver grafts, including steatotic livers. However, the current use of steatotic grafts in liver transplantation is less acceptable due to their higher susceptibility to ischemia-reperfusion (I/R) injury. To investigate the mechanism underlying the susceptibility of steatotic liver to I/R injury, we detected cell death markers and inflammation in clinical donor livers and animal models. We found that caspase-8-mediated hepatic apoptosis is activated in steatotic liver I/R. However, ablation of caspase-8 only slightly mitigated steatotic liver I/R injury without affecting inflammation. We further demonstrated that RIPK1 kinase induces both caspase-8-mediated apoptosis and cell death-independent inflammation. Inhibition of RIPK1 kinase significantly protects against steatotic liver I/R injury by alleviating both hepatic apoptosis and inflammation. Additionally, we found that RIPK1 activation is induced by Z-DNA binding protein 1 (ZBP1) but not the canonical TNFα pathway during steatotic liver I/R. Deletion of ZBP1 substantially decreases the steatotic liver I/R injury. Mechanistically, ZBP1 is amplified by palmitic acid-activated JNK pathway in steatotic livers. Upon I/R, excessive reactive oxygen species trigger ZBP1 activation by inducing its aggregation independent of the Z-nucleic acids sensing action in steatotic livers, leading to the kinase activation of RIPK1 and the subsequent aggravation of liver injury. Thus, ZBP1-mediated RIPK1-driven apoptosis and inflammation exacerbate steatotic liver I/R injury, which could be targeted to protect steatotic donor livers during transplantation.

Extracting double-quantum coherence in two-dimensional electronic spectroscopy under pump-probe geometry.

Two-dimensional electronic spectroscopy (2DES) can be implemented with different geometries, e.g., BOXCARS, collinear, and pump-probe geometries. The pump-probe geometry has the advantage of overlapping only two beams and reducing phase cycling steps. However, its applications are typically limited to observing the dynamics with single-quantum coherence and population, leaving the challenge to measure the dynamics of the double-quantum (2Q) coherence, which reflects the many-body interactions. We demonstrate an experimental technique in 2DES under pump-probe geometry with a designed pulse sequence and the signal processing method to extract 2Q coherence. In the designed pulse sequence, with the probe pulse arriving earlier than the pump pulses, our measured signal includes the 2Q signal as well as the zero-quantum signal. With phase cycling and data processing using causality enforcement, we extract the 2Q signal. The proposal is demonstrated with rubidium atoms. We observe the collective resonances of two-body dipole-dipole interactions in both the D1 and D2 lines.

Cross-phase modulation in two-dimensional spectroscopy.

Developing from transient absorption (TA) spectroscopy, two-dimensional (2D) spectroscopy with pump-probe geometry has emerged as a versatile approach for alleviating the difficulty in implementing 2D spectroscopy with other geometries. However, the presence of cross-phase modulation (XPM) in TA spectroscopy introduces significant spectral distortions, particularly when the pump and probe pulses overlap. We demonstrate that this phenomenon is extended to the 2D spectroscopy with pump-probe geometry and the XPM is induced by the interference of the two pump pulses. We present the oscillatory behavior of XPM in the 2D spectrum and its displacement with respect to the waiting time delay through both experimental measurements and numerical simulations. Additionally, we explore the influence of probe pulse chirp on XPM and discover that by compressing the chirp, the impact of XPM on the desired signal can be reduced.

Influence of Rotational Speed on Isothermal Piston Compression System.

An isothermal piston is a device that can achieve near-isothermal compression by enhancing the heat transfer area with a porous media. However, flow resistance between the porous media and the liquid is introduced, which cannot be neglected at a high operational speed. Thus, the influence of rotational speed on the isothermal piston compression system is analyzed in this study. A flow resistance mathematical model is established based on the face-centered cubic structure hypothesis. The energy conservation rate and efficiency of the isothermal piston are defined. The effect of rotational speed on resistance is discussed, and a comprehensive energy conservation performance assessment of the isothermal piston is analyzed. The results show that the increasing rate of the resistance work increases significantly proportional to the rotational speed, and the proportion of resistance work in the total work increases gradually and sharply. The total work including compression and resistance cannot be larger than the compression work under adiabatic conditions. The maximum rotational speed is 650 rpm.

A new terrein dimer and a new meroterpene from the mangrove endophytic fungus Lichtheimia sp.

A new terrein dimer named lichtheicol A (1) and a new meroterpene named lichtheiterpene A (2), were isolated from the mangrove endophytic fungus Lichtheimia sp. J2B1, together with 10 known compounds (3-12). The planar structures and absolute configurations of 1 and 2 were established by a combination of extensive spectroscopic data analyses and electronic circular dichroism (ECD) calculations. Compounds 4 and 5 exhibited marked inhibitory effects against butyrylcholinesterase (BuChE) with IC50 values of 0.71 and 0.53 µM, respectively.

Intramolecular redox cyclization reaction access to cinnolines from 2-nitrobenzyl alcohol and benzylamine via intermediate 2-nitrosobenzaldehyde.

A transition-metal-free intramolecular redox cyclization reaction for the synthesis of cinnolines has been developed from 2-nitrobenzyl alcohol and benzylamine. Mechanistic investigations disclosed the involvement of a key intramolecular redox reaction, followed by condensation, azo isomerization to hydrazone, cyclization, and aromatization to form the desired products. Notably, the formation of intermediate 2-nitrosobenzaldehyde and (E)-2-(2-benzylidenehydrazineyl) benzaldehyde plays an important role in this transformation.

Enantiodetection of Chiral Molecules via Two-Dimensional Spectroscopy.

Enantiodetection of chiral molecules is important to chemical reaction control and biological function designs. Traditional optical methods of enantiodetection rely on the weak magnetic-dipole or electric-quadrupole interactions, and in turn suffer from the weak signal and low sensitivity. We propose a new optical enantiodetection method to determine the enantiomeric excess via two-dimensional (2D) spectroscopy of the chiral mixture driven by three electromagnetic fields. The quantities of left- and right-handed chiral molecules are reflected by the intensities of different peaks on the 2D spectrum, separated by the chirality-dependent frequency shifts resulting from the relative strong electric-dipole interactions between the chiral molecules and the driving fields. Thus, the enantiomeric excess can be determined via the intensity ratio of the peaks for the two enantiomers.

A new species of freshwater crab of the genus Nanhaipotamon Bott, 1968 (Crustacea, Decapoda, Brachyura, Potamidae) from Longhai, Fujian Province, China.

A new species of freshwater crab of the genus Nanhaipotamon Bott, 1968 is described from Xiaye Village, Chengxiang Town, Longhai County, Zhangzhou City, Fujian Province, China. The new species is distinguished from congeners by the combination of characters of its carapace, third maxilliped, unequal chelipeds, triangular male abdomen and unique male first gonopod. Molecular evidence derived from partial mitochondrial 16S rRNA and COI genes also support the species as new.

lncRNA MCF2L-AS1/miR-105/ IL-1ß Axis Regulates Colorectal Cancer Cell Oxaliplatin Resistance.

BACKGROUND: Interactions between non-coding RNAs and mRNAs have been shown to play key roles in colorectal cancer (CRC) resistance to chemotherapeutic drugs, but the regulatory network of these ncRNA/mRNA interactions in the context of CRC cell resistance to oxaliplatin has yet to be fully defined. METHODS: MCF2L-AS1, miR-105, and IL-1ß expression levels were measured in cells and serum samples via qPCR, while ELISAs were additionally used to quantify IL-1ß levels in these samples. Interactions between MCF2L-AS1, miR-105, and IL-1ß were detected through pull-down, RNA immunoprecipitation, and luciferase reporter assays. Cellular viability and OXA IC50 values were established through MTT assays, while in vivo OXA resistance was assessed using a tumor xenograft model system. RESULTS: MCF2L-AS1 levels were significantly elevated in CRC patients that did not respond to chemotherapy and in CRC/OXA cells relative to responders and chemosensitive CRC cells. From a mechanistic perspective, miR-105 was identified as a MCF2L-AS1 target, with this miRNA, in turn, suppressing the expression of IL-1ß. Knocking down MCF2L-AS1 or overexpressing miR-105 was sufficient to alleviate CRC/OXA cell chemoresistance, while overexpressing IL-1ß reversed this effect. CONCLUSION: The MCF2L-AS1/miR-105/IL-1ß regulatory axis regulates the resistance of CRC cells to OXA treatment.

Design and Development of Hybrid Hydrogels for Biomedical Applications: Recent Trends in Anticancer Drug Delivery and Tissue Engineering.

The applications of hydrogels in biomedical field has been since multiple decades. Discoveries in biology and chemistry render this platform endowed with much engineering potentials and growing continuously. Novel approaches in constructing these materials have led to the production of complex hybrid hydrogels systems that can incorporate both natural and synthetic polymers and other functional moieties for mediated cell response, tunable release kinetic profiles, thus they are used and research for diverse biomedical applications. Recent advancement in this field has established promising techniques for the development of biorelevant materials for construction of hybrid hydrogels with potential applications in the delivery of cancer therapeutics, drug discovery, and re-generative medicines. In this review, recent trends in advanced hybrid hydrogels systems incorporating nano/microstructures, their synthesis, and their potential applications in tissue engineering and anticancer drug delivery has been discussed. Examples of some new approaches including click reactions implementation, 3D printing, and photopatterning for the development of these materials has been briefly discussed. In addition, the application of biomolecules and motifs for desired outcomes, and tailoring of their transport and kinetic behavior for achieving desired outcomes in hybrid nanogels has also been reviewed.

Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide.

Carbonyls and amines are yin and yang in organocatalysis as they mutually activate and transform each other. These intrinsically reacting partners tend to condense with each other, thus depleting their individual activity when used together as cocatalysts. Though widely established in many prominent catalytic strategies, aminocatalysis and carbonyl catalysis do not coexist well, and, as such, a cooperative amine/carbonyl dual catalysis remains essentially unknown. Here we report a cooperative primary amine and ketone dual catalytic approach for the asymmetric α-hydroxylation of ß-ketocarbonyls with H2O2. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H2O2 via an oxaziridine intermediate derived from an in-situ-generated ketimine. Ultimately, this enamine-oxaziridine coupling facilitated the highly controlled α-hydroxylation of several ß-ketocarbonyls in excellent yield and enantioselectivity. Notably, late-stage hydroxylation for peptidyl amide or chiral esters can also be achieved with high stereoselectivity. In addition to its operational simplicity and mild conditions, this cooperative amine/ketone catalytic approach also provides a new strategy for the catalytic activation of H2O2 and expands the domain of typical amine and carbonyl catalysis to include this challenging transformation.

Modified procedure for prolapse and hemorrhoids: Lower recurrence, higher satisfaction.

BACKGROUND: Hemorrhoidal prolapse is a common benign disease with a high incidence. The treatment procedure for prolapse and hemorrhoids (PPH) remains an operative method used for internal hemorrhoid prolapse. Although it is related to less pos-operative pain, faster recovery and shorter hospital stays, the postoperative recurrence rate is higher than that of the Milligan-Morgan hemorrhoidectomy (MMH). We have considered that recurrence could be due to shortage of the pulling-up effect. This issue may be overcome by using lower purse-string sutures [modified-PPH (M-PPH)]. AIM: To compare the therapeutic effects and the patients' satisfaction after M-PPH, PPH and MMH. METHODS: This retrospective cohort study included 1163 patients (M-PPH, 461; original PPH, 321; MMH, 381) with severe hemorrhoids (stage III/IV) who were admitted to The 2nd Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University from 2012 to 2014. Early postoperative complications, efficacy, postoperative anal dysfunction and patient satisfaction were compared among the three groups. Established criteria were used to assess short- and long-term postoperative complications. A visual analog scale was used to evaluate postoperative pain. Follow-up was conducted 5 years postoperatively. RESULT: Length of hospital stay and operating time were significantly longer in the MMH group (8.05 ± 2.50 d, 19.98 ± 4.21 min; P < 0.0001) than in other groups. The incidence of postoperative anastomotic bleeding was significantly lower after M-PPH than after PPH or MMH (1.9%, 5.1% and 3.7%; n = 9, 16 and 14; respectively). There was a significantly higher rate of sensation of rectal tenesmus after M-PPH than after MMH or PPH (15%, 8% and 10%; n = 69, 30 and 32; respectively). There was a significantly lower rate of recurrence after M-PPH than after PPH (8.7% and 18.8%, n = 40 and 61; P < 0.0001). The incidence of postoperative anal incontinence differed significantly only between the MMH and M-PPH groups (1.3% and 4.3%, n = 5 and 20; P = 0.04). Patient satisfaction was significantly greater after M-PPH than after other surgeries. CONCLUSION: M-PPH has many advantages for severe hemorrhoids (Goligher stage III/IV), with a low rate of anastomotic bleeding and recurrence and a very high rate of patient satisfaction.

Highly multiplexed quantifications of 299 somatic mutations in colorectal cancer patients by automated MALDI-TOF mass spectrometry.

BACKGROUND: Detection of somatic mutations in tumor tissues helps to understand tumor biology and guide treatment selection. Methods such as quantitative PCR can analyze a few mutations with high efficiency, while next generation sequencing (NGS) based methods can analyze hundreds to thousands of mutations. However, there is a lack of cost-effective method for quantitatively analyzing tens to a few hundred mutations of potential biological and clinical significance. METHODS: Through a comprehensive database and literature review we selected 299 mutations associated with colorectal cancer. We then designed a highly multiplexed assay panel (8-wells covering 299 mutations in 109 genes) based on an automated MADLI-TOF mass spectrometry (MS) platform. The multiplex panel was tested with a total of 319 freshly frozen tissues and 92 FFPE samples from 229 colorectal cancer patients, with 13 samples also analyzed by a targeted NGS method covering 532 genes. RESULTS: Multiplex somatic mutation panel based on MALDI-TOF MS detected and quantified at least one somatic mutation in 142 patients, with KRAS, TP53 and APC being the most frequently mutated genes. Extensive validation by both capillary sequencing and targeted NGS demonstrated high accuracy of the multiplex MS assay. Out of 35 mutations tested with plasmid constructs, sensitivities of 5 and 10% mutant allele frequency were achieved for 19 and 16 mutations, respectively. CONCLUSIONS: Automated MALDI-TOF MS offers an efficient and cost-effective platform for highly multiplexed quantitation of 299 somatic mutations, which may be useful in studying the biological and clinical significance of somatic mutations with large numbers of cancer tissues.

Targeting Tumor Immunosuppressive Microenvironment for the Prevention of Hepatic Cancer: Applications of Traditional Chinese Medicines in Targeted Delivery.

Traditional Chinese Medicine (TCM) is one of the ancient and most accepted alternative medicinal systems in the world for the treatment of health ailments. World Health Organization recognizes TCM as one of the primary healthcare practices followed across the globe. TCM utilizes a holistic approach for the diagnosis and treatment of cancers. The tumor microenvironment (TME) surrounds cancer cells and plays pivotal roles in tumor development, growth, progression, and therapy resistance. TME is a hypoxic and acidic environment that includes immune cells, pericytes, fibroblasts, endothelial cells, various cytokines, growth factors, and extracellular matrix components. Targeting TME using targeted drug delivery and nanoparticles is an attractive strategy for the treatment of solid tumors and recently has received significant research attention under precise medicine concept. TME plays a pivotal role in the overall survival and metastasis of a tumor by stimulating cell proliferation, preventing the tumor clearance by the immune cells, enhancing the oncogenic potential of the cancer cells, and promoting tumor invasion. Hepatocellular Carcinoma (HCC) is one of the major causes of cancer-associated deaths affecting millions of individuals worldwide each year. TCM herbs contain several bioactive phytoconstituents with a broad range of biological, physiological, and immunological effects on the system. Several TCM herbs and their monomers have shown inhibitory effects in HCC by controlling the TME. This study reviews the fundamentals and applications of targeting strategies for immunosuppressing TME to treat cancers. This study focuses on TME targeting strategies using TCM herbs and the molecular mechanisms of several TCM herbs and their monomers on controlling TME.

Surface Engineered Metal-Organic Frameworks (MOFs) Based Novel Hybrid Systems for Effective Wound Healing: A Review of Recent Developments.

Wounds present serious medical complications and their healing requires strategies that promote angiogenesis, deposition of collagen as well as re-epithelialization of wounds. Currently used conventional wound healing strategies have become less effective due to various issues associated with them. Thus, novel strategies are needed to be developed for early and effective healing of wounds. Metal-organic frameworks (MOFs), formed by linking of metal ions through organic bridging ligands, are highly tunable hybrid materials and have attracted more considerable scientific attention due to their charming and prominent properties, such as abundant pore structures and multiple functionalities. Surface engineering of MOFs with unique ligands can overcome issues associated with conventional wound healing methods, thus resulting in early and effective wound healing. This review has been undertaken to elaborate wound healing, and the use of surface engineered MOFs for effective and rapid wound healing. The process of wound healing will be discussed followed by a detailed review of recent literature for summarizing applications of surface engineered MOFs for wound healing. MOFs wound healing will be discussed in terms of their use as antibacterial agents, therapeutic delivery vehicles, and dressing systems in wound healing.

Recent Advances in Biomaterials for the Treatment of Bone Defects.

Bone defects or fractures generally heal in the absence of major interventions due to the high regenerative capacity of bone tissue. However, in situations of severe/large bone defects, these orchestrated regeneration mechanisms are impaired. With advances in modern medicine, natural and synthetic bio-scaffolds from bioceramics and polymers that support bone growth have emerged and gained intense research interest. In particular, scaffolds that recapitulate the molecular cues of extracellular signals, particularly growth factors, offer potential as therapeutic bone biomaterials. The current challenges for these therapies include the ability to engineer materials that mimic the biological and mechanical properties of the real bone tissue matrix, whilst simultaneously supporting bone vascularization. In this review, we discuss the very recent innovative strategies in bone biomaterial technology, including those of endogenous biomaterials and cell/drug delivery systems that promote bone regeneration. We present our understanding of their current value and efficacy, and the future perspectives for bone regenerative medicine.

Role of Treg/Th17 Imbalance, Microbiota and miRNAs in Pancreatic Cancer: Therapeutic Options.

Pancreatic cancer is one of the most lethal kinds of cancer; numerous patients die from it every year all over the word. Fewer than 5% of people with pancreatic cancer survive death and recover. Recent evidence suggests that inflammation parameters, such as Th17 cells and Tregs, affect the progression and even the diagnosis and treatment of pancreatic cancer. In the inflammation process, T lymphocytes play an essential role in inflammation intensity, and related cytokines modulate immune responses in the tumor microenvironment. Their function is to establish a balance between destructive inflammation and defense against tumor cells via immune system, and Treg/Th17 imbalance is a common problem in this cancer. The role of microbiota in the development of some cancers is clear; microbiota may also be involved in the pancreatic cancer development. All risk factors for pancreatic cancer, such as chronic pancreatitis-related to microbiota, influence the acute or chronic immune response. Some evidence has been presented regarding the role of the immune response in carcinogenesis. In addition, miRNAs are very important in suppressing and stimulating the growth of cancer cells, and a variety of them have been identified. Some miRNAs are abnormally expressed in many cancers and have main roles as post-transcriptional regulators. They show oncogenic or tumor-suppressive functions by binding to marked mRNAs. In this review, we highlight recent findings regarding the role of Treg/Th17 imbalance, microbiota functions, and miRNAs performance in pancreatic cancer. We also present the evidence regarding therapeutic options.

The roles of tumor-associated macrophages in tumor angiogenesis and metastasis.

Tumor associated macrophages (TAMs) are the most frequent immune cells within tumor microenvironment (TME). There is growing evidence that TAMs are involved in tumor progression via multiple mechanisms. TAMs create an immunosuppressive TME by producing growth factors, chemokines, and cytokines which modulate recruitment of immune cells and inhibit anti-tumor responses. They also serve as angiogenesis promoting cells by production of pro-angiogenic factors and matrix metalloproteinases (MMPs) and vascular constructing which guarantee supplying oxygen and nutrients to solid tumor cells. Furthermore, TAMs play important functions in tumor metastasis through contributing to invasion, extravasation, survival, intravasation, and colonization of tumor cells. In this review, we summarized macrophage classification, TAMs polarization, and mechanisms underlying TAM-promoting angiogenesis and metastasis.

Metabolic Syndrome, as Defined Based on Parameters Including Visceral Fat Area, Predicts Complications After Surgery for Rectal Cancer.

BACKGROUND/OBJECTIVES: Metabolic syndrome (MetS) has become a major public health problem. However, few studies have examined the impact of MetS on the postoperative complications of colorectal cancer and the conclusions remain controversial. The present study aimed to investigate whether MetS, as defined based on visceral fat area (VFA) instead of BMI or waist circumference, would predict complications after surgery for rectal cancer. SUBJECTS/METHODS: We conducted a retrospective study of patients who underwent surgery for rectal cancer at our department between January 2013 and August 2018. Univariate and multivariate analyses evaluating the risk factors for postoperative complications were performed. A receiver operating characteristic curve analysis was used to determine the gender-specific cut-off values for VFA. RESULTS: A total of 381 patients were included in the study. The optimal cut-off values for VFA were 117.9 cm2 for men and 76.9 cm2 for women, and 153 patients were diagnosed as having MetS. The rate of postoperative complication was significantly higher in the MetS group than that in the non-MetS group (34.6% versus 15.8%, P < 0.001). The multivariate logistic regression analysis demonstrated that MetS (OR 3.712, P < 0.001), NRS 2002 scores ≥ 3 (OR 2.563, P = 0.001), and tumor located at the lower 1/3 (OR 3.290, P = 0.001) were independent risk factors for complications after surgery for rectal cancer. CONCLUSION: Metabolic syndrome, as defined based on parameters including visceral fat area, was an independent risk factor for complications after surgery for rectal cancer.