Presence Of Rh2 Research Articles

Catalytic Asymmetric Syntheses of Alkylidenecyclopropanes from Allenoates with Donor-Acceptor and Diacceptor Diazo Reagents.

The first diastereo- and enantioselective cyclopropanation reactions of electron-deficient allenes with donor-acceptor and diacceptor diazo reagents are described. The desired enantioenriched alkylidenecyclopropanes (ACPs) were obtained in high yields with high diastereo- and enantioselectivities in the presence of Rh2 ((S)-TCPTAD)4 or Rh2 ((R)-BTPCP)4 catalysts (up to 95 % yield, >95 : 5 d.r. and 99 : 1 e.r.). This methodology gave a direct access to ACPs bearing multiple electron-deficient substituents and allows to further expand the availability of ACPs chemistry. Interestingly, during the examination of the scope of this reaction, the asymmetric intramolecular C-H insertion reaction into tert-butyl group was observed as a side reaction with up to 94 : 6 e.r.

Ginsenoside Rh2 Regulates the CFAP20DC-AS1/MicroRNA-3614-3p/BBX and TNFAIP3 Axis to Induce Apoptosis in Breast Cancer Cells.

While a number of coding genes have explained the anticancer activity of ginsenoside Rh2, little is known about noncoding RNAs. This study was performed to elucidate the regulatory activity of long noncoding RNA (lncRNA) CFAP20DC-AS1, which is known to be downregulated by Rh2. MiR-3614-3p, which potentially binds CFAP20DC-AS1, was screened using the LncBase Predicted program, and the binding was verified by assaying the luciferase activity of a luciferase/lncRNA recombinant plasmid construct. The competitive endogenous RNA (ceRNA) relationship of the two RNAs was further validated by quantitative PCR after deregulation of each RNA using siRNA. The effect of miRNA and target genes on the MCF-7 cancer cell growth was determined by monitoring proliferation and apoptosis in the presence of Rh2 after deregulating the corresponding gene. The miRNA decreased the luciferase activity of the luciferase/CFAP20DC-AS1 fusion vector, confirming the binding. SiRNA-based deregulation of CFAP20DC-AS1 attenuated the expression of miR-3614-3p and vice versa. In contrast to CFAP20DC-AS1, miR-3614-3p was upregulated by Rh2, inhibiting proliferation but stimulating apoptosis of the MCF-7 cells. Target genes of miR-3614-3p, BBX and TNFAIP3, were downregulated by Rh2 and the miRNA but upregulated by the lncRNA. Rh2 inhibits CFAP20DC-AS1, which obscures the association of the lncRNA with miR-3614-3p, resulting in the suppression of oncogenic BBX and TNFAIP3. Taken together, the Rh2/CFAP20DC-AS1/miR-3614-3p/target gene axis contributes to the antiproliferation activity of Rh2 in cancer cells.

Ginsenoside Rh2 upregulates long noncoding RNA STXBP5-AS1 to sponge microRNA-4425 in suppressing breast cancer cell proliferation

BackgroundGinsenoside Rh2, a major saponin derivative in ginseng extract, is recognized for its anticancer activities. Compared to coding genes, studies on long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) that are regulated by Rh2 in cancer cells, especially on competitive endogenous RNA (ceRNA) are sparse. MethodsLncRNAs whose promoter DNA methylation level was significantly altered by Rh2 were screened from methylation array data. The effect of STXBP5-AS1, miR-4425, and RNF217 on the proliferation and apoptosis of MCF-7 breast cancer cells was monitored in the presence of Rh2 after deregulating the corresponding gene. The ceRNA relationship between STXBP5-AS1 and miR-4425 was examined by measuring the luciferase activity of a recombinant luciferase/STXBP5-AS1 plasmid construct in the presence of mimic miR-4425. ResultsInhibition of STXBP5-AS1 decreased apoptosis but stimulated growth of the MCF-7 cells, suggesting tumor-suppressive activity of the lncRNA. MiR-4425 was identified to have a binding site on STXBP5-AS1 and proven to be downregulated by STXBP5-AS1 as well as by Rh2. In contrast to STXBP5-AS1, miR-4425 showed pro-proliferation activity by inducing a decrease in apoptosis but increased growth of the MCF-7 cells. MiR-4425 decreased luciferase activity from the luciferase/STXBP5-AS1 construct by 26%. Screening the target genes of miR-4425 and Rh2 revealed that Rh2, STXBP5-AS1, and miR-4425 consistently regulated tumor suppressor RNF217 at both the RNA and protein level. ConclusionLncRNA STXBP5-AS1 is upregulated by Rh2 via promoter hypomethylation and acts as a ceRNA, sponging the oncogenic miR-4425. Therefore, Rh2 controls the STXBP5-AS1/miR-4425/RNF217 axis to suppress breast cancer cell growth.

Rh(II)-catalyzed formal [3+3] cycloaddition of diazonaphthoquinones and propargyl alcohols: Synthesis of 2,3-dihydronaphtho-1,4-dioxin derivatives

A Rh(II)-catalyzed formal [3+3] cyclization of diazonaphthoquinones and propargyl alcohol is reported to afford 2,3-dihydro-1,4-benzodioxins. Various terminal propargyl alcohols react with diazonapthoquinone in the presence of Rh2(OAc)4 to give the corresponding dihydrodioxins in good to high yields. However, dihydrodioxins are not formed in the reaction of internal propargyl alcohols, and the O–H insertion product and 2,5-dihydrofurans are formed as the main product(s) depending on the terminal substituent. 2,3-Dihydro-1,4-benzodioxins are proposed to be formed via Rh(II)-catalyzed intermolecular oxonium ylide formation and subsequent 6-exo-dig cyclization with the internal alkynyl group.

Ginsenoside Rh2 activates α-catenin phosphorylation to inhibit lung cancer cell proliferation and invasion.

The efficacy of ginsenoside Rh2 (Rh2) in cancer therapy has been reported; however, its function in lung cancer remains unknown. To analyze the role of Rh2 in the inhibition of lung cancer cell proliferation in the present study, protein expression levels of E-cadherin, vimentin, β-catenin, Smo, Gli1, and α-catenin were assessed by western blotting, whilst mRNA expression levels of TCF7 FZD8, Smo, Gli1, Gli2, and Gli3 were determined by reverse transcription-quantitative PCR in the A549 cell line. Phosphorylation sites were detected by proteomic methods and cell proliferation was analyzed by MTT assay. The present study revealed that Rh2 treatment significantly inhibited cell proliferation. Western blotting indicated that the expression levels of E-cadherin were increased and vimentin was downregulated in Rh2-treated cells compared with control cells. Treatment of A549 cells with Rh2 suppressed phosphorylation of five distinct proteins and increased phosphorylation of nine proteins. Among them, the phosphorylation of α-catenin at S641 was significantly induced. Rh2 treatment suppressed the expression levels of key genes involved in Wnt (Wnt3, transcription factor 7 and frizzled class receptor 8) and hedgehog [smoothened, frizzled class receptor (Smo), GLI family zinc finger (Gli)1, Gli2, and Gli3] signaling. Immunoblotting results indicated that β-catenin, Smo and Gli1 protein expression levels were also suppressed by treatment with Rh2 compared with control treatment. Expression of α-catenin S641D, a phosphomimetic form of α-catenin, inhibited the accumulation of β-catenin and Gli1 and inhibited cell proliferation and invasion. Furthermore, knockdown of β-catenin (CTNNB1) or Gli1 with specific small interfering RNAs inhibited cell proliferation, whereas overexpression of these genes had an opposite effect. Additionally, overexpression of β-catenin or Gli1 activated cell proliferation, even in the presence of Rh2, suggesting that Rh2 affects A549 cell proliferation through inhibition of Wnt and hedgehog signaling by phosphorylation of α-catenin at S641. Together, these data suggested that Rh2 treatment may inhibit the proliferation of A549 lung cancer cells. Further exploration of the underlying mechanism by which Rh2 inhibits cell proliferation is warranted.

Rh‐Catalyzed Aminative Dearomatization of Naphthols with Hydroxylamine‐O‐Sulfonic Acid (HOSA)

An efficient Rh‐catalyzed aminative dearomatization of naphthols was achieved. In the presence of Rh2(esp)2 and HOSA as an inexpensive and readily available aminating reagent, a series of unprotected α‐amino‐β‐naphthalenones was afforded in good yields under mild reaction conditions. This reaction features good tolerance of functional groups and multi mmol‐scale reaction.

Rhodium-Catalyzed Intramolecular Cyclopropanation of α-Diazo β-Keto Nitriles Containing an Unsaturated Substituted Cycloalkyl Group

Several α-diazo β-keto nitriles bearing trans-2-allyl-, -vinyl-, or -phenylcycloalkyl groups were prepared and their intramolecular cyclopropanation reactions were examined. In the presence of Rh2(OAc)4 (1 mol%) as a catalyst, the allyl- and vinyl-substituted precursors were found to undergo cyclopropanation smoothly at ambient temperature to afford novel tricyclic α-keto cyclopropyl nitriles in 47–88% yields with diastereomeric ratios ranging from 79:21 to >99:1. On the other hand, the catalytic reactions of the phenyl-containing analogues did not give any cyclopropyl products, but instead provided functionalized hexa­hydrophenanthrene or tetrahydrocyclopentanaphthalene derivatives in quantitative yields.

Total synthesis of myriocin and mycestericin D employing Rh(II)-catalyzed C[sbnd]H amination followed by stereoselective alkylation

Total synthesis of myriocin and mycestericin D was achieved using the Du Bois Rh(II)-catalyzed CH amination of a sulfamate and subsequent alkylation as a key step. The reaction of a sulfamate with PhI(OAc)2 and MgO in the presence of Rh2(OAc)4 gave oxathiazinane N,O-acetal as the sole product in high yield. Alkylation of N,O-acetal using vinylmagnesium bromide in the presence of ZnCl2 proceeded stereoselectively to provide an oxathiazinane bearing a quaternary chiral center in high yield. Myriocin and mycestericin D were synthesized from a common synthetic intermediate. This route includes the first application of the Du Bois procedure for constructing a quaternary chiral center.

Two Distinct Cyclizations of 2-Propenyl-1-ethynyl Benzenes with Aryldiazo Esters Using Au and Rh/Au Catalysts Respectively

This work reports the development of two catalytic cyclizations of 2-propenyl-1-ethynylbenzenes with aryldiazo esters. Cationic gold catalyst produces 2-substituted 3-alkenyl-1H-indenes with substrates over a reasonable scope. Our mechanistic study suggests that arydiazo esters attack at the cyclopropyl moieties of gold carbene intermediates, followed by skeletal rearrangement of resulting intermediates. In the presence of Rh2(esp)2 additive, the same gold catalyst alters the chemoselectivity of these reactants to afford tetrahydro-1H-cyclopropa[b]naphthalenes with excellent stereoselectivity. Herein, Rh(II) catalyst catalyzed the reactions of the same 1,6-enynes with diazo species to form cyclopropenes initially, and a cationic Au(I) catalyst allows their subsequent reactions with the tethered alkenes. Preferable E-selectivity and synergistic effects of Au/Rh catalysts are rationalized in a postulated mechanism.

ChemInform Abstract: Chiral Lewis Acid‐Catalyzed Enantioselective Cycloadditions Between Indoles and Cyclic Carbonyl Ylides Derived from Diazodiketone or Diazoketoester Derivatives.

Asymmetric 1,3-dipolar cycloaddition reactions between N-methylindoles and several cyclic carbonyl ylides that were derived from diazodiketone or diazoketoester precursors in the presence of both achiral Rh and chiral lanthanoid metal catalysts are described. For the six-membered cyclic carbonyl ylides derived from 1-diazo-5-aryl-2,5-pentanedione precursors, the cycloaddition reactions were carried out using Rh2(OAc)4 (2 mol %) and the chiral Pybox-Ph2-Lu(OTf)3 complex (10 mol %) as catalysts, resulting in high enantioselectivities (83% to >98% ee (exo)) along with relatively good exo-selectivities (exo:endo = 65:35 to 94:6) and yields (63-85%). For the five-membered cyclic carbonyl ylide derived from 1-diazo-2,4-pentandione precursor, the cycloaddition reaction with 5-bromo-1-methylindole was carried out in the presence of Rh2(OAc)4 (2 mol %) and the chiral Pybox-Ph2-Er(OTf)3 complex (30 mol %) as catalysts, resulting in relatively good enantioselectivity (78% ee) and endo-selectivity (endo:exo = 81:19).

Stereoselective Total Synthesis of Myriocin Using Rhodium(II)‐Catalyzed C−H Amination Followed by Alkylation

AbstractThe stereoselective total synthesis of myriocin was achieved by using the Du Bois RhII‐catalyzed C−H amination of sulfamate 6, derived from diethyl l‐tartrate, and a subsequent alkylation. The reaction of sulfamate 6 with PhI(OAc)2 and MgO in the presence of Rh2(OAc)4 gave an oxathiazinane N,O‐acetal as the sole product in high yield. Alkylation of the N,O‐acetal with vinylmagnesium bromide in the presence of ZnCl2 proceeded stereoselectively to provide an oxathiazinane bearing a quaternary chiral center in high yield. This route includes the first application of the Du Bois procedure for the construction of a quaternary chiral center.

Chiral Lewis Acid-Catalyzed Enantioselective Cycloadditions between Indoles and Cyclic Carbonyl Ylides Derived from Diazodiketone or Diazoketoester Derivatives.

Asymmetric 1,3-dipolar cycloaddition reactions between N-methylindoles and several cyclic carbonyl ylides that were derived from diazodiketone or diazoketoester precursors in the presence of both achiral Rh and chiral lanthanoid metal catalysts are described. For the six-membered cyclic carbonyl ylides derived from 1-diazo-5-aryl-2,5-pentanedione precursors, the cycloaddition reactions were carried out using Rh2(OAc)4 (2 mol %) and the chiral Pybox-Ph2-Lu(OTf)3 complex (10 mol %) as catalysts, resulting in high enantioselectivities (83% to >98% ee (exo)) along with relatively good exo-selectivities (exo:endo = 65:35 to 94:6) and yields (63-85%). For the five-membered cyclic carbonyl ylide derived from 1-diazo-2,4-pentandione precursor, the cycloaddition reaction with 5-bromo-1-methylindole was carried out in the presence of Rh2(OAc)4 (2 mol %) and the chiral Pybox-Ph2-Er(OTf)3 complex (30 mol %) as catalysts, resulting in relatively good enantioselectivity (78% ee) and endo-selectivity (endo:exo = 81:19).

What factors cause the complete substrate-controlled selectivity in Rh2(Piv)4-catalyzed cycloadditions of 1,2,3-triazoles with isocyanates or isothiocyanates

DFT studies on Rh2(Piv)4-catalyzed cycloadditions of 1,2,3-triazoles with isocyanates or isothiocyanates show that 1, 2, 3-triazoles undergo ring opening → coordination of Rh2(Piv)4 → dissociation of N2 to give Rh2(Piv)4-azavinyl carbene, where Rh2(Piv)4 exerts a stabilizing effect on azavinyl carbene. The formed Rh2(Piv)4-azavinyl carbene prefers to nucleophilically cyclize with CN bond of isocyanatobenzene to give the imidazolone, rather than CO bond of isocyanatobenzene to give the oxazolimine. In comparison, Rh2(Piv)4-azavinyl carbene preferentially cyclize with CS bond of isothiocyanatobenzene to give the thiazole, instead of CN bond of isothiocyanatobenzene to give the thioimidazolone. The nucleophilic capacity follows CS > CN > CO trend, which is the key selective origin of these reactions. The presence of Rh2(Piv)4 would help to form the carbene and to stabilize it via donating its d-electron into the azavinyl carbene, which is another selective origin of these reactions.

Rhodium acetate/base-catalyzed N-silylation of indole derivatives with hydrosilanes

In the presence of Rh(2)(OAc)(4) (OAc = acetate) and TBA(2)WO(4) (TBA = tetra-n-butylammonium), the N-silylation of indole derivatives with hydrosilanes efficiently proceeded to give the corresponding N-silylated indoles in high yields. Pyrrole and carbazole were also N-silylated with the combined catalysts.

ChemInform Abstract: Diastereoselectivity Switch in Cooperatively Catalyzed Three‐Component Reactions of an Aryldiazoacetate, an Alcohol, and a β,γ‐Unsaturated α‐Keto Ester.

AbstractIn the presence of Rh2(OAc)4/AgBF4 the title reaction provides the erythro products with high diastereoselectivity.

Ginsenoside Rh2 induces ligand-independent Fas activation via lipid raft disruption

Lipid rafts are plasma membrane platforms mediating signal transduction pathways for cellular proliferation, differentiation and apoptosis. Here, we show that membrane fluidity was increased in HeLa cells following treatment with ginsenoside Rh2 (Rh2), as determined by cell staining with carboxy-laurdan (C-laurdan), a two-photon dye designed for measuring membrane hydrophobicity. In the presence of Rh2, caveolin-1 appeared in non-raft fractions after sucrose gradient ultracentrifugation. In addition, caveolin-1 and GM1, lipid raft landmarkers, were internalized within cells after exposure to Rh2, indicating that Rh2 might disrupt lipid rafts. Since cholesterol overloading, which fortifies lipid rafts, prevented an increase in Rh2-induced membrane fluidity, caveolin-1 internalization and apoptosis, lipid rafts appear to be essential for Rh2-induced apoptosis. Moreover, Rh2-induced Fas oligomerization was abolished following cholesterol overloading, and Rh2-induced apoptosis was inhibited following treatment with siRNA for Fas. This result suggests that Rh2 is a novel lipid raft disruptor leading to Fas oligomerization and apoptosis.

Rh‐Catalyzed Transannulation of Pyridotriazoles with Alkynes and Nitriles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Rh-catalyzed transannulation of pyridotriazoles with alkynes and nitriles.

Rh-catalyzed transannulation of pyridotriazoles with alkynes and nitriles.

Synthesis of New Enantiopure Fluorinated Phenylcyclopropanecarboxylates – Potential Chiral Dopants for Liquid‐Crystal Compositions

AbstractThe reaction of α‐fluorostyrene (1a) with methyl phenyldiazoacetate in the presence of Rh2(OAc)4 gave a 64:36 mixture of diastereomeric monofluorinated cyclopropanes 5a and 6a. When using chiral RhII catalysts Rh2(TBSP)4 (7) and Rh2(DOSP)4 (8), the products were obtained enantioselectively in up to >99 % ee for both (1R,2R)‐5a and (1R,2S)‐6a. The fluorocyclopropane derivatives are of interest as dopants to induce chirality in liquid‐crystal mixtures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Rh2(oac)4-catalyzed reactions of methyl diazoacetate with 1,3-oxazolidines and 1,3-oxathiolanes

Methoxycarbonylcarbene generated by catalytic decomposition of methyl diazoacetate in the presence of Rh2(OAc)4, is regioselectively inserted into the C(2)-O bond of 3-alkyl-2-phenyl-1,3-oxazolidines and into the C(2)-S bond of 2-phenyl-1,3-oxathiolane. Study by the competitive reaction method demonstrated that the relative reactivity toward the insertion of the methoxycarbonylcarbene fragment into the C-heteroatom bond increases in the series of 1,3-dioxolane, 1,3-oxazolidine, and 1,3-oxathiolane.