Total Synthesis of the Flavonoid Natural Product Houttuynoid A

Perplexing Polyphenolics: The Isolations, Syntheses, Reappraisals, and Bioactivities of Flavonoids, Isoflavonoids, and Neoflavonoids from 2016 to 2022

Flavonoids, isoflavonoids, neoflavonoids, and their various subcategories are polyphenolics-an extensive class of natural products. These compounds are bioactive and display multiple activities, including anticancer, antibacterial, antiviral, antioxidant, and neuroprotective activities. Thus, these compounds can serve as leads for therapeutic agents or targets for complex synthesis; they are coveted and routinely isolated, characterized, biologically evaluated, and synthesized. However, data regarding the compounds' sources, isolation procedures, structural novelties, bioactivities, and synthetic schemes are often dispersed and complex, a dilemma this review aims to address. To serve as an easily accessible guide for researchers wanting to apprise themselves of the latest advancements in this subfield, this review summarizes seventy-six (76) articles published between 2016 and 2022 that detail the isolation and characterization of two hundred and forty-nine (249) novel compounds, the total and semisyntheses of thirteen (13) compounds, and reappraisals of the structures of twenty (20) previously reported compounds and their bioactivities. This article also discusses new synthetic methods and enzymes capable of producing or modifying flavonoids, isoflavonoids, or neoflavonoids.

Total Synthesis of Lineaflavones A, C, D, and Analogues

The first total synthesis of lineaflavones A, C, D, and their analogues has been accomplished. The key synthetic steps include aldol/oxa-Michael/dehydration sequence reactions to assemble the tricyclic core, Claisen rearrangement and Schenck ene reaction to construct the key intermediate, and selective substitution or elimination of tertiary allylic alcohol to obtain natural compounds. In addition, we also explored five new routes to synthesize fifty-three natural product analogues, which can contribute to a systematic structure-activity relationship during biological evaluation.

A structure-specific small molecule inhibits a miRNA-200 family member precursor and reverses a type 2 diabetes phenotype

MicroRNA families are ubiquitous in the human transcriptome, yet targeting of individual members is challenging because of sequence homology. Many secondary structures of the precursors to these miRNAs (pri- and pre-miRNAs), however, are quite different. Here, we demonstrate both in vitro and in cellulis that design of structure-specific small molecules can inhibit a particular miRNA family member to modulate a disease pathway. The miR-200 family consists of five miRNAs, miR-200a, -200b, -200c, -141, and -429, and is associated with type 2 diabetes (T2D). We designed a small molecule that potently and selectively targets pre-miR-200c's structure and reverses a pro-apoptotic effect in a pancreatic β cell model. In contrast, an oligonucleotide targeting the RNA's sequence inhibited all family members. Global proteomics and RNA sequencing analyses further demonstrate selectivity for miR-200c. Collectively, these studies establish that miR-200c plays an important role in T2D, and small molecules targeting RNA structure can be an important complement to oligonucleotides.

NHC-catalyzed enantioselective C2-functionalization of 3-hydroxychromenones via α,β-unsaturated acyl azoliums

A novel synthetic method for enantioselective C2-functionalization of 3-hydroxychromenones promoted by N-heterocyclic carbenes via the formation of α,β-unsaturated acyl azolium intermediates, which occurs with Coates-Claisen rearrangement is established. This synthetic strategy enabled the rapid assembly of enantiomerically enriched δ-hydroxychromenone-derived esters/amides under mild conditions with good to excellent yields and broad substrate scope.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.

Synthesis of 2-Substituted Benzo[b]furans/furo-Pyridines Catalyzed by NiCl2

The first Ni-catalyzed tandem synthesis of 2-substituted benzo[b]furans/furo-pyridines from 2-halophenols and 1-alkynes was explored under Cu-free and phosphine-free conditions. The protocol was carried out with NiCl2/5-nitro-1, 10-phenanthroline in DMA (N,N-dimethylacetamide) at 120 °C. It was found to be simple, cost effective, and have a wide substrate scope. Additionally, the method is compatible with heteroaryl substrates, resulting in the formation of 2-substituted benzo[b]furans/furo-pyridines in reasonable to good yields.

Maternal intelligence quotient and motor development in early childhood: The mediating role of mother's education

AIM

To examine the association between maternal intelligence quotient (IQ) and early childhood motor development and whether maternal education mediates this relationship.

METHODS

Data were collected prospectively in the Ma'anshan Birth Cohort study. Maternal IQ was assessed using the Wechsler Adult Intelligence Scale-Revised by China (WAIS-RC). Information on baseline characteristics and maternal education was obtained from questionnaires and medical records. The study outcome was motor development evaluated at 18 months by the Third Edition of Ages and Stages Questionnaire. Logistic regression analyses and mediation analyses were used.

RESULTS

Of 2739 valid subjects (84% follow-up), the rate of developmental delay was 3.1% in the gross motor domain and 6.2% in the fine motor domain. The mean value for maternal IQ was 96.2 (standard deviation 10.6). About 40.3% of the mothers had secondary education or less, while 59.7% had a college education. Mothers with higher IQ had a significantly higher educational level and had children with better motor development. Maternal education significantly mediated the association between maternal IQ and fine motor development. There was a direct effect of maternal IQ on gross motor development, but the mediation effect of maternal education was not found.

CONCLUSIONS

Maternal IQ was associated with motor development. Maternal education played an important role in reducing the disparities in fine motor development among children of different maternal IQs.

Asymmetric Synthesis of Chiral Flavan-3-Ols

Flavan-3-ols are a series of natural products widely present in plants and show versatile biological activities. The structures of such compounds are characterized by owing two adjacent chiral centers and three rings. Their interesting structures and promising biological activities have driven increasing research developments toward the preparation of enantioenriched flavan-3-ols. This review summarizes the recent approaches for the asymmetric synthesis of chiral flavan-3-ols from two strategies in the construction of chiral centers. The key steps in the synthetic protocol involve Sharpless asymmetric dihydroxylation, Shi asymmetric epoxidation and Sharpless asymmetric epoxidation.