Biomimetic Synthesis of Rhytidenone A and Mode of Action of Cytotoxic Rhytidenone F

The rhytidenone family comprises spirobisnaphthalene natural products isolated from the mangrove endophytic fungus Rhytidhysteron rufulum AS21B. The biomimetic synthesis of rhytidenone A was achieved by a Michael reaction/aldol/lactonization cascade in a single step from the proposed biosynthetic precursor rhytidenone F. Moreover, the mode of action of the highly cytotoxic rhytidenone F was investigated. The pulldown assay coupled with mass spectrometry analysis revealed the target protein PA28γ is covalently attached to rhytidenone F at the Cys92 residue. The interactions of rhytidenone F with PA28γ lead to the accumulation of p53, which is an essential tumor suppressor in humans. Consequently, the Fas-dependent signaling pathway is activated to initiate cellular apoptosis. These studies have identified the first small-molecule inhibitor targeting PA28γ, suggesting rhytidenone F may serve as a promising natural product lead for future anticancer drug development.     

“Lotus” Domain Formation by the Hydrolysis Reaction of Phospholipase D to Phospholipid Monolayer

Hydrolysis rection of L-α-dipalmitoylphosphatidylcholine(L-DPPC)monolayer with phospholipase D (PLD) has been investigated by Brewster angle microscopy (BAM) combined with the film balance.It has been found that the L-DPPC domains were changed into the “lotus“ structure by PLD.It suggests that the hydrolysis reaction is incomplete and the products together with the nonreacted materials undergo a molecular rearrangement at the interface.     

A Solvothermal Route to Cu2O Nanocubes and Cu Nanoparticles

IntroductionSynthesis of Cu2O and Cu nanostructures has beenactively researched for many decades because bothCu2O and Cu are important industrial materials on ac-count of their novel physical and chemical properties.In particular,Cu2O is a p-type metal ox…     

Divergent Biomimetic Total Syntheses of Ganocins A–C,Ganocochlearins C and D,and Cochlearol T

A divergent synthetic approach to six Ganoderma meroterpenoids, namely ganocins A–C, ganocochlearins C and D, and cochlearol T, has been developed for the first time. This synthetic route features a two-phase strategy which includes early-stage rapid construction of a common planar tricyclic intermediate followed by highly selective late-stage transformations into various Ganoderma meroterpenoids. Key to the strategy are a bioinspired intramolecular hetero-Diels–Alder reaction and Stahl-type oxidative aromatization, allowing efficient formation of the common tricyclic phenol intermediate. A nucleophilic dearomatization of the phenol unit, combined with a regioselective 1,4-reduction of the resulting dienone, enabled rapid access to ganocins B and C. Additionally, site-selective Mukaiyama hydration, followed by an intramolecular oxa-Michael addition/triflation cascade, served as a key strategic element in the chemical synthesis of ganocin A.     

A New Type of Biomimetic Model: Design, Synthesis and Characterization of Imidazolium Bis-Estrogen

Biomimeticmoleculessuchasartificialenzpoesandreceptorshavebeenattractinggrowingattention[1].Duetosteroidalplanar,largeandrigidhydrophobicbackbone,anditsnaturalchiralsource,steroid-basedartificialbiomimeticmodelssuchasthebis-androgenandthebis-bileacidhavebeenspeciallyfOcused..[2-5]inrecentyears-HerewerePOrtforthefirsttimeonthedesignandsynthesisofimidazoliumbis-estrogens4a'basanewtyPeofbiomimeticmodel,whichPOssessPOtentialmLiltiplebiomimeticfunctions.Theschemeisout1inedasfollows.Themode1s4a'…     

Ni-Catalyzed Cross-Coupling of 2-Iodoglycals and 2-Iodoribals with Grignard Reagents: A Route to 2-C-Glycosides and 2’-C-Nucleosides

The synthesis of 2-C-glycals and 2-C-ribals was achieved in good yields using a nickel-catalyzed cross-coupling between 2-iodoglycals and 2-iodoribal respectively and Grignard reagents. The prepared 2-C-glycals and ribals were then transformed into 2-C-2-deoxyglycosides, 2-C-diglycosides and 2’-C-2’-deoxynucleosides. The developed method was applied to the synthesis of a 2-chloroadenine 2’-deoxyribonucleoside – a structural analogue of cladribine (Mavenclad®, Leustatin®) and clofarabine (Clolar®, Evoltra®), two compounds used in the treatment of relapsing-remitting multiple sclerosis and hairy cell leukemia.     

Total Synthesis of Suberitines A–D Featuring Tunable Biomimetic Late-Stage Oxidative Dearomatization and Acetalization

Aaptaminoids are a unique family of marine alkaloids bearing a benzo[de][1,6]-naphthyridine core. This work describes the first total synthesis of suberitines A–D ( 1 – 4 ), four typical dimeric natural aaptaminoids, employing a step-saving bidirectional strategy. Key methods applied in the total synthesis include a cationic cascade to construct the bis-isoquinoline(s) with Hendrickson reagent-mediated Friedel-Crafts-type cyclization and eliminative aromatization, and a Bronsted acid-promoted Vilsmeier cyclization to generate the naphthyridine(s). The conditionally tunable PIDA-mediated oxidative dearomatization and subsequent methanolysis or hydrolysis successfully served as a powerful biomimetic tool to elaborate the essential oxygenated functionalities of suberitines A–D ( 1 – 4 ) in proper solvent-combinations at the final stage of total synthesis. The biomimetic proposal employed in the late-stage redox interchanges of related natural products was eventually supported by the isolation of synthetic intermediate 23 a as a natural product from the same natural source. Biological screening revealed that five of the synthetic samples including two natural suberitines and three full-skeleton natural product-like intermediates exhibited low micromolar inhibitory activities against the growth of cancer cell line K562.     

A facile pathway to 2-furfurylketones

2-(Chloromethyl)furan as an electrophile reacted with lithium trialkylalkyllylbo-rates,followcl by the oxidation with H_2O_2 under basic condition to afford 2-furfurylketonesin good yields.This provides a new method for the preparation of 2-furfurylkctoncs.     

“One-pot” cascade approach to 5,6-dihydroindolizines and indolizines from pyrrole-2-carbaldehydes and nitroethylenes

Simple and practical reactions of pyrrole-2-carbaldehydes with nitroethylenes provide either the 5,6-dihydroindolizines or the indolizines in one pot, depending on the reaction temperature. Additionally, a plausible mechanism for the entire sequence is proposed.     

In reply to “A query on the Mg2p of MgO”

Research on Chemical Intermediates -     

A One-pot Procedure to Prepare Ethynylferrocene and Iodoethynylferrocene

IntroductionFerrocene-containing compounds have been widely used as important probes to investigate the electron transfer/transport properties of the molecular materials1. Recently, this technique was employed in molectronics research, where the ferrocenes were incorporated on the ends of conjugated molecular wires, and the electron transfer/transport abilities of the molecular wires were conveniently studied by electrochemical method2. Ethynylferrocene and iodoethynylferrocene were two import…     

Discoveries and Challenges en Route to Swinhoeisterol A

In this work, a full account of the authors’ synthetic studies is reported that culminated in the first synthesis of 13(14→8),14(8→7)diabeo-steroid swinhoeisterol A as well as the related dankasterones A and B, 13(14→8)abeo-steroids, and periconiastone A, a 13(14→8)abeo-4,14-cyclo-steroid. Experiments are described in detail that provided further insight into the mechanism of the switchable radical framework reconstruction approach. By discussing failed strategies and tactics towards swinhoeisterol A, the successful route that also allowed an access to structurally closely related analogues, such as Δ²²-24-epi-swinhoeisterol A, is eventually presented.     

Simultaneous Removal of COS and H_2S at Low Temperatures over Nanoparticle a-FeOOH Based Catalysts

Catalysts using a-FeOOH nanoparticles as the active ingredient were tested by a microreactor-chromatography assessing apparatus at atmospheric pressure between 25 and 60C with a gas hourly space velocity of 10,000 h-1, while the removal performance of H2S with catalysts was investigated using the thermal gravimetric method. The results show that the catalysts are highly active for COS hydrolysis at low temperatures (<60C) and high gas hourly space velocity, and the highest activity can reach 100%. The catalyst is particularly stable for 12 h, and no deactivation is observed. Nanoparticle a-FeOOH prepared using hydrated iron sulfate shows higher COS hydrolysis activity, and the optimum calcination temperature for the catalyst is 260C. In addition, the catalysts can remove COS and H2S simultaneously, and 60C is favorable for the removal of H2S. The compensation effect exists in nanoparticle-based catalysts.     

Response to “About acceptance and rejection zones”

Desimoni and Brunetti raise some questions about the use of Eurachem/CITAC guide, because the Eurachem/CITAC guide does not discuss an ISO recommendation before performing a test, it should be decided whether it is to be a test for conformity or a test for non-conformity. In response, it is pointed out that although this recommendation is not discussed explicitly, it is of necessity covered by the decision rule that describes how the measurement uncertainty will be taken into consideration with regard to accepting or rejecting a product according to its specification and the result of a measurement. In addition, they propose the introduction of an ‘inconclusive’ zone. We do not think that this is necessary, since the Eurachem/CITAC guide takes the view that action on rejection should be covered by the ‘decision rule’ and this can make equivalent provision for confirmation or interpretation.     

A new synthetic approach to benzoporphyrins and Kröhnke type porphyrin-2-ylpyridines

The reaction of 2-formyl-5,10,15,20-tetraphenylporphyrin with aryl methyl ketones and ammonium acetate, in the presence of La(OTf)(3), affords benzoporphyrins and 2-(2,6-diarylpyridin-4-yl)porphyrins. This methodology was used to prepare, for the first time, a 2-(2,2':6',2'-terpyridin-4'-yl)porphyrin. The structures of two 2-(2,6-diarylpyridin-4-yl)porphyrins were confirmed by single-crystal X-ray diffraction.     

Sensitized Photooxidation of Ortho-Prenyl Phenol: Biomimetic Dihydrobenzofuran Synthesis and Total 1O2 Quenching†

The sensitized photooxidation of ortho-prenyl phenol is described with evidence that solvent aproticity favors the formation of a dihydrobenzofuran [2-(prop-1-en-2-yl)-2,3-dihydrobenzofuran], a moiety commonly found in natural products. Benzene solvent increased the total quenching rate constant (k_T) of singlet oxygen with prenyl phenol by ~10-fold compared to methanol. A mechanism is proposed with preferential addition of singlet oxygen to prenyl site due to hydrogen bonding with the phenol OH group, which causes a divergence away from the singlet oxygen ‘ene’ reaction toward the dihydrobenzofuran as the major product. The reaction is a mixed photooxidized system since an epoxide arises by a type I sensitized photooxidation.     

A novel chemical route to SiO_2 nanowires

A white substance was got by directly heating TiSi powder on Ti foil, under Ar+O2 atmosphere. ED, EDX, SEM and HRTEM studies reveal that the white substance consists of amorphous SiO2nanowires of smooth surface and uniform diameter (40-90 nm). X-ray-induced luminescent emission experiment shows that two broad peaks are at 430 and 570 nm. A one-dimensional growth mechanism, on the basis of the one-dimensional thermal flow during nanowire formation, is discussed.     

ZrOCl2 Catalysed Chemoselective Conversion of Aldehydes to geminal-Diacetates and Their Cleavage： A Mild and Efficient Method

ZrOCl2 was found to be an effective Lewis acid catalyst for the solventless chemoselective conversion of aldehydes into geminal-diacetates in high yields at room temperature. Regeneration of the aldehydes from the acetals was also achieved using the same catalyst in water. The beneficial effect of microwave irradiation on the reaction was also described. Other advantages are the very low loading of catalyst, high yields achieved even on a gram scale, and considerably shortened reaction time compared to the conventional method.     

A comparative study in structure and reactivity of “FeO_x-on-Pt” and “NiO_x-on-Pt” catalysts

Oxide nanostructures grown on noble metal surfaces are often highly active in many reactions,in which the oxide/metal interfaces play an important role.In the present work,we studied the surface structures of Fe Ox-on-Pt and Ni Ox-on-Pt catalysts and their activity to CO oxidation reactions using both model catalysts and supported nanocatalysts.Although the active Fe O1x structure is stabilized on the Pt surface in a reductive reaction atmosphere,it is prone to change to an Fe O2x structure in oxidative reaction gases and becomes deactivated.In contrast,a Ni O1x surface structure supported on Pt is stable in both reductive and oxidative CO oxidation atmospheres.Consequently,CO oxidation over the Ni O1x-on-Pt catalyst is further enhanced in the CO oxidation atmosphere with an excess of O2.The present results demonstrate that the stability of the active oxide surface phases depends on the stabilization effect of the substrate surface and is also related to whether the oxide exhibits a variable oxidation state.