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The stereochemistry of the lipophilic side chain of (+)-rakicidin F had not been determined until recently. Using our lithiation-borylation methodology ("assembly line synthesis") we were able to efficiently prepare the all-syn isomer as well as the C-21 epimer of the side chain, and comparison with the natural product suggested that the natural product had all-syn stereochemistry. Completion of the total synthesis using a macrolactamization of the northern amide enabled us to confirm Wang and Chen's stereochemical findings for the structure of (+)-rakicidin F.

The identification of the beneficial pharmacokinetic properties of aza-spirocycles has led to the routine incorporation of these highly rigid and three-dimensional structures in pharmaceuticals. Herein, we report an operationally simple synthesis of spirocyclic dihydropyridines via an electrophile-induced dearomative semi-pinacol rearrangement of 4-(1′-hydroxycyclobutyl)pyridines. The various points for diversification of the spirocyclization precursors, as well as the synthetic utility of the amine and ketone functionalities in the products, provide the potential to rapidly assemble medicinally relevant spirocycles.

Benzoxazolyl linked meta- and para-substituted new chemical entities (5a–5h) featuring thiazolidinedione, rhodanine, hydantoin, and thiohydantoin moieties were synthesized and characterized by 1H NMR, 13C NMR, FT-IR, and HRMS spectral studies. In addition, all compounds were screened for α-glucosidase inhibitory activity and further supported by molecular docking studies carried out at the active site of α-glucosidase (PDB code: 3TOP) in comparison to acarbose used as a standard drug. Out of eight tested compounds, 5d was found as the most active inhibitor of α-glucosidase (IC50 = 9.48 ± 0.36 µM), having rhodanine moiety substituted at meta-position of the phenyl ring.

Dysoxylactam A is a 17-membered macrocyclic lipid which has been found to dramatically reverse multidrug resistance in cancer cells. Three previous syntheses have been reported in 15-17 steps. Using iterative lithiation-borylation reactions as the key C−C bond forming and stereocontrolling steps, we now describe an 11-step synthesis of dysoxylactam A. The complete sequence only required a total of five chromatographic purifications and used minimal protecting groups making it both rapid and efficient.

A highly diastereoselective, visible-light-induced [3 + 2] cycloaddition between N-sulfonyl cyclopropylamines and electron-deficient olefins is reported. The reactions proceed via the oxidation of a sulfonamide aza-anion by an organic photocatalyst to generate a nitrogen-centered radical. Strain-induced ring opening and intermolecular addition to the olefin generate an intermediate carbon-centered radical that is reduced to an anion prior to 5-exo cyclization. This enables a highly diastereoselective construction of trans-cyclopentanes possessing synthetically useful functional groups.

A visible-light photoinduced fragmentation borylation of O-phthalimido cycloalkanols with bis(catecholato)diboron is described. Structurally diverse keto and formyloxy alkyl boronic esters are shown to be conveniently prepared by radical-mediated ring opening of cyclic alcohols and hemiacetals, respectively. The reactions proceed under mild conditions in the absence of additives or photocatalysts, display excellent functional group tolerance, and are shown to allow cleavage of 4-, 5-, 6-, and 7-membered ring substrates. The mechanism proceeds via sequential homolytic N–O and C–C bond cleavages, the latter of which involves β-scission of an alkoxy radical, generating a carbonyl and an alkyl radical that is trapped by the diboron reagent. Spectroscopic studies suggest direct photoexcitation of either the phthalimide or diboron substrates with blue light can initiate a radical chain mechanism.

A 12-step asymmetric synthesis of thromboxane B2 (TxB2) from 2,5-dimethoxytetrahydrofuran is described. The synthesis employs our organocatalytic aldol reaction of succinaldehyde to give a key bicyclic enal intermediate. From here, the synthetic strategy involves a conjugate addition of an alkenyl side chain to the bicyclic enal, Baeyer–Villiger oxidation, and a highly Z-selective Wittig olefination of a hemiacetal. Key to success was minimizing redox operations and the manipulation of functional groups in the correct order.

A novel series of N-methyl/benzyl-substituted benzimidazolyl-linked para-substituted benzyl-based compounds containing 2,4-thiazolidinediones, dimethyl malonate (DMM), and diethyl malonate (DEM) 17–27 were designed, docked, synthesized, and evaluated for their antidiabetic activity studies. Structures of all the synthesized compounds were confirmed through 1H NMR, 13C NMR, FTIR, and mass spectrometry. Four targeted compounds (17–18 and 22–23) showed good inhibitory potential in the range of 4.10 ± 0.01 to 9.12 ± 0.06 µM. Furthermore, synthesized compounds 17–27 were evaluated for their antioxidant potential and compared with standard ascorbic acid and results showed that compound 18 (EC50 = 0.176 ± 0.002 mM) being the most active. Compounds 17–18 and 22–23 exhibited prominent antidiabetic as well as antioxidant activity. Compound 18 was considered a promising candidate for this series. The designed molecules were docked into α-glucosidase protein (PDB Code. 3TOP) to develop a correlation with the α-glucosidase inhibition studies and were also additionally docked into PPARγ proteins (PDB ID: 2PRG) with rosiglitazone (standard drug) to study their PPARγ binding affinity in comparison with rosiglitazone and to classify these compounds for their PPARγ agonistic behavior.

A simple, rapid, accurate and precise RP-HPLC method was developed for the determination of stigmasterol in botanical extract of Ficus deltoidea. Separation was achieved with acetonitrile and acetic acid in water (75:25% v/v) in isocratic mode at 210 nm. Single sharp peak of standard stigmasterol was detected at retention time 3.17 min which overlay with the peak of plant extract at 3.14 min. The calibration curve was found to be linear in a concentration range of 2–10 μg/ml with correlation coefficient of 0.998. The LOD and LOQ were found to be 1.50 μg/ml and 4.55 μg/ml respectively. Accuracy and precision was determined with overall recovery of 99.6–100.1% for stigmasterol and RSD values in both intra-day and inter-day repeatability assay lesser than 0.340%, respectively. The robustness study also indicated that there is no influence of minor changes in detecting wavelength and flow rate of mobile phase on the response.

The three-component coupling of benzylamines, boronic esters, and 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione (PTAD) is reported. The boronate complex formed from an ortho-lithiated benzylamine and a boronic ester undergoes a stereospecific 1,2-metalate rearrangement/anti-S N 2′ elimination in the presence of an N-activator to provide a dearomatized tertiary boronic ester. Interception of this dearomatized intermediate with a dienophile leads to stereopredictable cycloaddition reactions to generate highly complex three-dimensional boron-containing molecular structures. When enantioenriched α-methyl-substituted benzylamines are employed, the corresponding cycloaddition adducts are formed with excellent enantiospecificities.

The Matteson reaction involves treatment of a chiral boronic ester with (dichloromethyl)lithium in the presence of ZnCl2 which leads to an α–chloroboronic ester with very high diastereoselectivity. The origin of selectivity has now been investigated using modern computational analysis. The explanation for selectivity was previously based on steric repulsions in the transition state but the new study has identified a novel Cl··H electrostatic interaction which is only present in one of the two possible transition states. It is believed that this attractive interaction is critical in controlling the stereochemical outcome of the process. Furthermore, this more complete model can now be used to rationalize the disparity in reactivity (C–migration vs O–migration) occasionally observed in diastereomeric boron ate complexes, and why substrates devoid of the key hydrogen bond react with low stereocontrol.

Bicyclo[1.1.1]pentanes (BCPs) have found application as bioisosteres of aromatic rings in drug development. However, catalytic construction of this motif with adjacent stereocenters with high enantioselectivity from readily available starting materials still constitutes a significant synthetic challenge. Herein we report a direct stereoselective synthesis of α-chiral allylic BCPs by 1,3-difunctionalization of [1.1.1]propellane with Grignard reagents and allyl carbonates using iridium catalysis. This mild protocol proceeds via initial organometallic addition to [1.1.1]propellane followed by asymmetric allylic substitution, providing the products with high enantioselectivities over a broad range of substrates. Further derivatization of the products demonstrates the applicability of this method to the preparation of structurally diverse libraries of chiral BCP derivatives.

The synthesis of the chiral sulfide isothiocineole from limonene and elemental sulfur on multi-gram scale and its alkylation to make >50 g of the corresponding benzylsulfonium salt are described. The application of this salt to the sulfur ylide-mediated asymmetric epoxidation of aldehydes and the asymmetric aziridination of imines on a >5 g scale is demonstrated. Irish Research Council Science Foundation Ireland University of Bristol Marie-Curie Action COFUND

Furan- and indole-derived boronate complexes react with alkyl iodides under radical (photoredox) or polar (SN2) conditions to generate three-component alkylation products with high efficiency and complete stereospecificity. The methodology allows the incorporation of versatile functional groups such as nitriles, ketones, esters, sulfones, and amides, providing rapid access to complex chiral heteroaromatic molecules in enantioenriched form. Interestingly, while indolyl boronate complexes react directly with alkyl halides in a polar pathway, furyl boronates require photoredox catalysis. Careful mechanistic analysis revealed that the boronate complex not only serves as a substrate in the reaction but also acts as a reductive quencher for the excited state of the photocatalyst.

N-Benzyl cytisine undergoes an efficient C(6)-N(7) cleavage via directed C(6) lithiation, borylation and oxidation to provide a "privileged" heterocyclic core unit comprising a highly functionalised, cis-3,5-disubstituted piperidine in enantiomerically pure form. The potential offered by this unit as a means to explore chemical space has been evaluated and methods have been defined (and illustrated) that allow for selective manipulation of N(1), C(3'), and the pyridone N. The pyridone core can also be diversified via bromination (at C(3'') and C(5'')) which is complementary to direct C-H activation based on Ir-catalyzed borylation to provide access to C(4''). The use of a boronate-based 1,2-migration as an alternative trigger to mediate C(6)-N(7) cleavage of cytisine was evaluated but failed. However, the stability of the intermediate boronate opens a new pathway for the elaboration of cytisine itself using both Matteson homologation and Zweifel olefination.

Drug resistant bacteria pose a major health concern and affect a large section of global population. Antibacterial drug discovery has stagnated owing to multiple factors including unattractive returns for major pharmaceutical companies. Thus, discovery of effective antibacterial drugs against drug-resistant bacteria is an urgent unmet need affecting healthcare systems globally. In this study, fluorine-containing 2,3-diarylquinolines (4a-l) and non-fluorinated analog 4m were synthesized utilizing environmentally benign chemistry of arenediazonium salts and arynes for regioselective installation of aryl groups at C-2 and C-3 positions, respectively. In vitro antibacterial evaluation against various Gram-negative and Gram-positive bacteria revealed inhibitory activity of majority of these compounds against Gram-positive S. aureus ATCC 29213. Compounds 4e, 4i, 4j and 4l were most potent inhibitors with MIC values of 10.95−24.0 µM. None of the compounds inhibited Gram-negative bacteria. 4e, 4i and 4l also displayed low levels of cytotoxicity against Vero cells, therefore, offering high safety profiles. Importantly, 4e, 4i and 4l exhibited equipotent inhibition of Methicillin and Vancomycin-resistant S. aureus, rendering them potential hits for further development. Molecular docking studies with topoisomerase II DNA gyrase demonstrated significant interactions of these inhibitors with target protein, which provided valuable insights into their potent antibacterial activity.

The coupling of ortho- and para-phenols with secondary and tertiary boronic esters has been explored. In the case of para-substituted phenols, after reaction of a dilithio phenolate species with a boronic ester, treatment with Ph3BiF2 or Martin's sulfurane gave the coupled product with complete enantiospecificity. The methodology was applied to the synthesis of the broad spectrum antibacterial natural product (−)-4-(1,5-dimethylhex-4-enyl)-2-methyl phenol. For ortho-substituted phenols, initial incorporation of a benzotriazole on the phenol oxygen atom was required. Subsequent ortho-lithiation and borylation gave the coupled product, again with complete stereospecificity.

The veterinary drug Alfaprostol and prostaglandin PGF2α have been synthesized in just nine steps. The strategy involved the conjugate addition of an alkyne to a bicyclic enal, available in three steps by a proline-catalyzed aldol reaction of succinaldehyde. In the case of Alfaprostol, this resulted in the shortest synthesis reported to date. For PGF2α, this approach improved our previous route by making the 1,4-addition and ozonolysis more operationally simple.

A novel series of benzoxazolyl linked benzylidene based rhodanine and their cyclic analogs were synthesized, characterized and evaluated for their α-amyloglucosidase inhibitory activity. Out of eight target compounds, two compounds (4b and 5b) displayed potent inhibitory activity against α-amyloglucosidase with IC50 values in the range of 0.24 ± 0.01–0.94 ± 0.01 µM as compared to standard drug acarbose. Among all the tested compounds, compound 5b containing rhodanine at 3-position of phenyl was found to be the most active inhibitor of α-amyloglucosidase. Docking studies showed the existence of potential H-bonding interactions between synthesized compounds and α-glucosidase which might be responsible for good biological activity.

New nano-sized (1N) and single crystal (1) of 2[Co(NH3)5N3](H2I2O10)∙ 2H2O] complex salt was synthesized by sonochemical and classical method, and was characterized by elemental analysis, IR, UV/ Visible spectroscopy, X-ray powder diffraction. Morphology and particle size of 1N was determined by SEM and zeta-sizer. Single crystal X-ray analysis performed for 1 revealed a monoclinic C2/c space group. The crystal structure is built from layers-like regions of cations and anion-water that are connected via N-H...O hydrogen bonds. The nano-sized 2[Co(NH3)5N3](H2I2O10)∙2H2O] complex salt was examined towards the dye ability of cotton, wool and silk fabrics. A good variation in the color demonstrates that 1N can be used as a pigment for printing as well as a mordant dye.

The Zweifel olefination is a powerful method for the stereoselective synthesis of alkenes. The reaction proceeds in the absence of a transition-metal catalyst, instead taking place by iodination of vinyl boronate complexes. Pioneering studies into this reaction were reported in 1967 and this short review summarizes developments in the field over the past 50 years. An account of how the Zweifel olefination was modified to enable the coupling of robust and air-stable boronic esters is presented followed by a summary of current state of the art developments in the field, including stereodivergent olefination and alkynylation. Finally, selected applications of the Zweifel olefination in target-oriented synthesis are reviewed.1 Introduction2.1 Zweifel Olefination of Vinyl Boranes2.2 Zweifel Olefination of Vinyl Borinic Esters2.3 Extension to Boronic Esters3.1 Introduction of an Unsubstituted Vinyl Group3.2 Coupling of α-Substituted Vinyl Partners3.3 Syn Elimination4 Zweifel Olefination in Natural Product Synthesis5 Conclusions and Outlook

Replacement of wheat flour with varying levels of flaxseed flour (0–30%) on nutritional, functional and antioxidant properties of cookies was investigated. Cookies produced from composite flour mixes were significantly (p

A method for the conjunctive functionalization of vinyl boronate complexes with electrophiles is described. The overall process represents a three-component coupling between a vinyl boronic ester, carbon nucleophile and an electrophile, thus affording complex multifunctionalized products from simple starting materials. The diastereoselectivity (syn or anti) of this process is strongly dependent upon the nature of the electrophile.

To celebrate the 20th anniversary of the Bristol Synthesis Meeting, EurJOC invited the speakers of the past meetings to contribute an article to this Cluster Issue Unfortunately, this year's meeting had to be cancelled due to the ongoing pandemic of coronavirus disease 2019 (COVID‐19) Guest Editor Varinder Aggarwal, reflects on the rich history of the past 19 meetings

Celebrating the life of Stuart Warren.

A stereodivergent coupling reaction between vinyl halides and boronic esters is described. This coupling process proceeds without a transition‐metal catalyst, instead proceeding by electrophilic selenation or iodination of a vinyl boronate complex followed by stereospecific syn or anti elimination. Chiral, nonracemic boronic esters could be coupled with complete enantiospecificity. The process enables the highly stereoselective synthesis of either the E or Z alkene from a single isomer of a vinyl coupling partner.

The interleukin (IL)-20 subfamily of cytokines consists of IL-19, IL-20, IL-22, IL-24, and IL-26, and the expression of IL-20, IL-22, and IL-24 is reported to be higher in the colon of patients with ulcerative colitis. Although the receptors for these cytokines are highly expressed in the colon epithelium, their effects on epithelial renewal are not clearly understood. This study evaluated the effects of IL-20, IL-22, and IL-24 in epithelial renewal using the LS174T human colon cancer epithelial cell line. LS174T cells were treated with IL-20, IL-22, and IL-24 (25, 50, and 100 ng/mL) and a live-cell imaging system was used to evaluate the effects on cell proliferation. Following treatment, the signaling pathways contributing to cell proliferation were investigated through Western blotting in LS174T cells and downstream transcriptional changes through qRT-PCR in LS174T cells, and RNA-Seq in primary murine intestinal epithelial cells. Our results demonstrated that only IL-22 promoted LS174T cell proliferation, mediated via extracellular-signal-regulated kinase (ERK)1/2-mediated downstream regulation of p90RSK, c-Jun, and transcriptional changes of TRIM15 and STOM. IL-22 also promoted expression of ERK1/2-independent genes such as DDR2, LCN2, and LRG1, which are known to be involved in cell proliferation and migration. This study suggests that IL-22 induces cell proliferation in highly proliferative cells such as intestinal epithelial cells.

Soil properties are significantly influenced by the addition of biochar. Biochar improves soil quality as it increases the soil alkalinity, surface negative charge, nutrient retention capacity, porosity, organic carbon content and cation exchange capacity (CEC). The present research based on pot study was carried out in October 2015 to April 2016 with Prosopis juliflora biochar. We investigated the effect of different concentrations of biochar (1%, 5% and 10%) and polyaromatic hydrocarbons (50 mg/kg naphthalene and 100 mg/kg phenanthrene) on various physico-chemical parameters of sandy soil. Biochar application significantly helps to reduce the soil bulk density by 8.40%, 13.95% and 17.61%, respectively, as compared to control. Similarly, percent soil space was effectively decreased with increased biochar application rate from 8.4% to 17%. Porosity and water holding capacity were significantly increased with biochar application rate (0% < 1% p ≤ 0.05) results were observed in case of increase in pH and electrical conductivity values in biochar-amended and non-biochar amended soil samples. CEC and soil organic carbon values were significantly increased from 26.54 to 33.18% and 38.54 to 51.63%, respectively, in 10% biochar-amended soil as compared to biochar non-amended soil. However, biochar nourishes soil that could be safely applied in agriculture for improvement of soil health and crop yield.

An enantiospecific coupling between alkylboronic esters and lithiated aryl hydrazines is described. The reaction proceeds under transition-metal-free conditions and is promoted by acylation of a hydrazinyl arylboronate complex, which triggers a N–N bond cleavage with concomitant 1,2-metalate rearrangement. Judicious choice of the acylating agent enabled the synthesis of ortho- and para-substituted anilines with essentially complete enantiospecificity from a wide range of boronic ester substrates.

The inhibition of amyloid-β (Aβ) aggregation is a promising approach towards therapeutic intervention for Alzheimer’s disease (AD). Thirty eight tetrapeptides based upon Aβ39-42 C-terminus fragment of the parent Aβ peptide were synthesized. The sequential replacement/modification employing unnatural amino acids imparted scaffold diversity, augmented activity, enhanced blood brain barrier permeability and offered proteolytic stability to the synthetic peptides. Several peptides exhibited promising protection against Aβ aggregation-mediated-neurotoxicity in PC-12 cells at doses ranged between 10 μM and 0.1 μM, further confirmed by the thioflavin-T fluorescence assay. CD study illustrate that these peptides restrict the β-sheet formation, and the non-appearance of Aβ42 fibrillar structures in the electron microscopy confirm the inhibition of Aβ42 aggregation. HRMS and ANS fluorescence spectroscopic analysis provided additional mechanistic insights. Two selected lead peptides 5 and 16 depicted enhanced blood-brain penetration and stability against serum and proteolytic enzyme. Structural insights into ligand-Aβ interactions on the monomeric and proto-fibrillar units of Aβ were computationally studied. Promising inhibitory potential and short sequence of the lead peptides offers new avenues for the advancement of peptide-derived therapeutics for AD.

Re-investigation of the l-proline catalyzed double aldol cascade dimerization of succinaldehyde for the synthesis of a key bicyclic enal intermediate, pertinent in the field of stereoselective prostaglandin synthesis, is reported. The yield of this process has been more than doubled, from 14 % to a 29 % isolated yield on a multi-gram scale (32 % NMR yield), through conducting a detailed study of the reaction solvent, temperature, and concentration, as well as a catalyst screen. The synthetic utility of this enal intermediate has been further demonstrated through the total synthesis of Δ12-prostaglandin J3, a compound with known anti-leukemic properties.

Polypropionates are important structural motifs in nature and are commonly made by iterative aldol or crotylation methodologies. Herein, an alternative strategy is presented in which stereochemically predefined building blocks, bearing appropriate functionality, are coupled together using a lithiation-borylation methodology with complete stereocontrol. The building blocks comprise lithiated carbamates acting as donors, and boronic esters acting as acceptors. The acceptor building blocks contain β-hydroxyl groups masked as silyl groups to avoid elimination of the boronate intermediates. Subsequent oxidation of both the boron and silyl moieties can then deliver an array of polypropionate fragments with full stereochemical control, including the synthetically challenging anti-anti isomers.

A concise synthesis of stereodefined C-substituted morpholines, piperazines, azepines, and oxazepines in moderate to excellent yields (27% to 75%) is reported by reaction of 1,2- or 1,3-amino alcohol/1,2- or 1,3-diamine with an α-phenylvinylsulfonium salt. High levels of regio- and diastereoselectivity (from 2:1 to >20:1) are observed through judicious choice of base (Cs2CO3) and solvent (CH2Cl2). Reactions are performed at ambient temperature and open to air and do not require anhydrous solvent. The deprotection of the N-sulfonamide protecting groups (N-Ts and N-Ns) is also demonstrated. Factors affecting regio- and diastereocontrol are discussed.

Oxidative palladium-catalyzed reaction conditions have been developed to allow for regioselective and stereoselective coupling of allylic boronic esters with a range of carbon-, oxygen-, and nitrogen-based nucleophiles. Studies into the mechanism of the reaction have shown that the key transmetalation step occurs with retention of stereochemistry, since overall inversion is observed.

Boron-ate complexes derived from primary and secondary boronic esters and aryllithiums have been isolated, and the kinetics of their reactions with carbenium ions studied. The second-order rate constants have been used to derive nucleophilicity parameters for the boron-ate complexes, revealing that nucleophilicity increased with (i) electron-donating aromatics on boron, (ii) neopentyl glycol over pinacol boronic esters, and (iii) 12-crown-4 ether.

International audience; The iterative homologation of boronic esters using chiral lithiated benzoate esters and chloromethyllithium has been applied to the highly efficient syntheses of two natural products, (+)-kalkitoxin and (+)-hydroxyphthioceranic acid. The chiral lithiated benzoate esters (>99% ee) were generated from the corresponding stannanes, which themselves were prepared by Hoppe–Beak deprotonation of ethyl 2,4,6-triisopropyl-benzoate with s-BuLi in the presence of (+)- or (−)-sparteine and trapping with Me3SnCl followed by recrystallization. In addition, it was found that purification between several homologations could be avoided, substantially increasing both chemical and manpower efficiency. In the case of (+)-kalkitoxin, six iterative homologations were conducted on commercially available p-MeOC6H4CH2Bpin to build up the core of the molecule before the C–B bond was converted into the desired C–N bond, without purification of intermediates. In the case of (+)-hydroxyphthioceranic acid, 16 iterative homologations were conducted on p-MeOC6H4Bpin with only four intermediate purifications before oxidation of the C–B bond to the desired alcohol. The stereocontrolled and efficient syntheses of these complex molecules highlight the power of iterative chemical synthesis using boronic esters.

Allium schoenoprasum L. (family Amaryllidaceae), commonly known as chives has great culinary value besides being used as ethnomedicine. This review emphasises on phytochemistry and pharmacological activities of A. schoenoprasum, and discusses the future opportunities for systematic investigations. Scientific evaluation of chives validates its traditional claims and demonstrates diverse pharmacological potential including an anti-inflammatory, anticancer, antioxidant, anthelmintic and antihypertensive. Though phytochemical studies revealed the presence of sulphur and phenolic compounds, flavonoids, saponin and steroidal glycosides yet methodical research to identify bioactive compounds is required. This review confirms the medicinal importance of A. schoenoprasum and could stimulate future research on its unexplored aspects, especially identification of bioactive compounds and related mechanisms and safety, which might develop it as a drug.