Search

We have achieved a divergent access to seven/five-membered rings based on a [1,6]-hydride shift/cyclization process from benzylidenemalonate with an o-alkoxymethyl group. Whereas Yb(OTf)3 afforded benzoxepines (with a seven-membered ring) selectively, indanes (with a five-membered ring) were the main products when Sc(OTf)3 was employed.

We have achieved a sequential hydride-shift-triggered double C(sp3)-H bond functionalization at a position adjacent to an oxygen atom and a benzylic/aliphatic position through the employment of substrates with a dialkyl group in the alkyl chain, which enabled the highly diastereoselective synthesis of fused tetrahydropyrans.

A K2CO3-promoted transition-metal-free C–N coupling reaction was developed. When a solution of 1-(2-aminophenyl)-8-iodo­naphthalenes in DMSO was treated with 2.5 equivalents of K2CO3 and 5.0 equivalents of MeI, intramolecular C–N coupling reaction proceeded smoothly even at low temperature (room temperature) to afford various heteroaromatic compounds in good chemical yields. Additional experiments suggested that this reaction might have proceeded through an unusual SNAr reaction between haloarenes and a bulky tertiary amine moiety.

Herein we report a diastereoselective synthesis of medium-sized carbocycle-fused piperidines via [1,n (n = 6, 7)]-[1,5]-sequential hydride shift triggered double C(sp3)-H bond functionalization. When cinnamylidene malonates having N,N-dibenzyl propylamine moiety were treated with 5 mol % of Yb(OTf)3, a [1,6]-[1,5]-sequential hydride shift/cyclization process proceeded to afford seven-membered carbocycle-fused piperidines with excellent diastereoselectivities. This sequential system was applicable to the synthesis of eight-membered carbocycle-fused piperidines by an unprecedented [1,7]-[1,5]-sequential hydride shift/cyclization process.

A Sc(OTf)3-catalyzed activation of a single C–F bond in a CF3 group is described. This reaction has two interesting features: (1) the synthesis of difluoromethylene compounds through Lewis acid-cat...

Heterologous expression of a unique biosynthetic gene cluster (BGC) comprising a highly reducing polyketide synthase and stand-alone thioesterase genes in Aspergillus oryzae enabled us to isolate a novel 34-membered polyene macrolide, phaeospelide A (1). This is the first isolation of a fungal polyene macrolide and the first demonstration of fungal aliphatic macrolide biosynthetic machinery. In addition, sequence similarity network analysis demonstrated the existence of a large number of BGCs for novel fungal macrolides.

A one-pot, highly diastereoselective synthesis of chroman derivatives with three contiguous stereogenic centers is described. In this reaction, three transformations (iminium formation/Morita-Bayli...

Developed herein is a diastereoselective synthesis of CF3-substituted spiroisochromans via C(sp3)-H bond functionalization involving sequential transformations ([1,5]-hydride shift/cyclization/elimination of MeOH/intramolecular Friedel-Crafts reaction).

We achieved a concise construction of seven- and eight-membered carbocycles via Lewis acid catalyzed C(sp3)–H bond functionalization. In these reactions, a quite rare [1,6 (or 7)]-hydride shift/cyclization process proceeded smoothly to afford seven- and eight-membered carbocycles with good chemical yields starting from substrates with high conformational freedom.

Highly stereoselective synthesis of tetralin-fused spirooxindoles with two contiguous stereogenic centers. In the present reaction, not only [1,5]-hydride shift/cyclization process, but also replacemnt of nitrogen atom to oxygen atom ocurred smoothly to give target structure with hydroxy grop in good chemical yields with good to excellent diastereoselectivities (up to d.r. = >20:1). Investigation of the reaction mechanism suggested that this “atom-replacement” event ocurred via the iminium cation intermediates.

We report herein a rapid access to 3-indolyl-1-trifluoromethyl-isobenzofurans via a [1,4]-hydride shift/cyclizatin/intermolecular nucleophilic addition reaction sequence. In this process, a Lewis acid promoted internal redox reaction ([1,4]-hydride shift/cyclization) followed by a Bronsted acid promoted intermolecular reaction (generation of cyclic oxonium cation/intermolecular Friedel–Crafts reaction) occurred to give various 3-indolyl-1-trifluoromethyl-isobenzofurans in good chemical yields.

We have achieved a sequential hydride-shift-triggered double C(sp

Through genome mining for fungal macrolide natural products, we discovered a characteristic family of putative macrolide biosynthetic gene clusters that contain a glycosylphosphatidylinositol-ethanolamine phosphate transferase (GPI-EPT) homologue. Through the heterologous expression of two clusters from Aspergillus kawachii and Colletotrichum incanum, new macrolides, including those with phosphoethanolamine or phosphocholine moieties, were formed. This study is the first demonstration of the tailoring steps catalyzed by GPI-EPT homologues in natural product biosynthesis, and it uncovers a new gene resource for phospholipid-resembling fungal macrolides.

A highly diastereoselective synthesis of tetralin-fused spirooxindole derivatives was described. Treatment of benzylidene oxindoles with a catalytic amount of Sc(OTf)3 in refluxing hexane afforded the target compounds in good chemical yields with excellent diastereoselectivities (up to >20:1). Detailed investigation of the reaction mechanism revealed that both interconversion of the two diastereomers and their solubility difference in reaction medium were the key to achieving excellent diastereoselectivities.

A novel skeletal rearrangement involving a [1,5]-alkylthio group transfer/cyclization sequence is described. Treatment of benzylidene malonates having a thioketal moiety at the homobenzyl position with a catalytic amount of Sc(OTf)3 afforded alkylthio group rearranged adducts in good chemical yields. Detailed investigation of the reaction mechanism revealed that an intramolecular conjugate addition/ring opening sequence (not through-space transfer) is the key to achieving this reaction.

Described herein is a chiral magnesium bisphosphate-catalyzed asymmetric double C(sp3)–H bond functionalization triggered by a sequential hydride shift/cyclization process. This reaction consists of stereoselective domino C(sp3)–H bond functionalization: (1) a highly enantio- and diastereoselective C(sp3)–H bond functionalization by chiral magnesium bisphosphate (first [1,5]-hydride shift), and (2) a highly diastereoselective C(sp3)–H bond functionalization by an achiral catalyst (Yb(OTf)3, second [1,5]-hydride shift).

We report a divergent synthesis of CF3-substituted fused skeletons based on precise control of the activation site through the selection of acid catalysts. When trifluoromethyl ketones with an ortho-phenethyl ether group were treated with a catalytic amount of Sc(OTf)3, a hydride shift triggered C(sp3)-H bond functionalization proceeded to give CF3-substituted isochromene derivatives by selective activation of the carbonyl group. In sharp contrast, CF3-substituted bicyclo[3.3.1]nonanes were obtained exclusively via the activation of ether oxygen initiated sequential reactions (nucleophilic attack of carbonyl oxygen, and intramolecular Friedel-Crafts reaction) under strong Bronsted acid catalysis (Tf2NH).

Described herein is the Bronsted acid-catalyzed double C(sp3)–H bond functionalization of alkyl phenethyl ether derivatives. In this process, a [1,5]-[1,5]-hydride shift occurred successively to afford tricyclic fused pyran derivatives in excellent chemical yields with excellent diastereoselectivities (up to >20 : 1). The key to achieve this reaction was the introduction of two methyl groups at the benzylic position, which was effective in both hydride shift processes: (1) the Thorpe–Ingold effect for the first hydride shift and (2) conformational control in the second hydride shift.

Described herein is the expeditious construction of multi-substituted indole skeletons via multiple hydrogen transfers. When ortho-amino ketoesters were treated with a catalytic amount of TiCl4 in the presence of 1.0 equivalent of dehydrating reagent, three types of hydrogen transfer processes ([1,5]-hydride shift, proton transfer, and [1,2]-hydride shift) occurred to give various 3-alkoxycarbonylindoles. Further study revealed that a [1,2]-alkyl shift instead of a [1,2]-hydride shift proceeded to afford 3-alkylindoles from the substrates with an amino group having tertiary carbons adjacent to a nitrogen atom.

A highly stereoselective synthesis of tetralin-fused spirooxindoles with two contiguous stereogenic centers was developed. In the present reaction, not only the [1,5]-hydride shift/cyclization process, but also the replacement of nitrogen atom by oxygen atom occurred smoothly to give target compounds with hydroxy group in good chemical yields with good to excellent diastereoselectivities (up to d.r. = >20:1). Investigation of the reaction mechanism suggested that this “atom replacement” event occurred via the iminium cation intermediates.

We report a highly diastereoselective synthesis of 1,3-disubstituted tetralin derivatives via Lewis acid catalyzed benzylic C(sp3)–H bond functionalization. The employment of Hf(OTf)4 as an acid catalyst was crucial in the reaction, and corresponding tetralins were obtained in good chemical yields with high to excellent diastereoselectivities (up to 13.3 : 1 d.r.).

We achieved a concise construction of 3-substituted quinolinone derivatives based on a ring recombination strategy. In this process, seven transformations involving two types of cyclization proceeded in one pot to afford various quinolinone derivatives in good to excellent chemical yields (up to 98%).

We achieved a concise construction of seven- and eight-membered carbocycles via Lewis acid catalyzed C(sp3)-H bond functionalization. In these reactions, a quite rare [1,6 (or 7)]-hydride shift/cyclization process proceeded smoothly to afford seven- and eight-membered carbocycles with good chemical yields starting from substrates with high conformational freedom.

Developed herein is a diastereoselective synthesis of CF

We report herein a highly efficient kinetic resolution of PHANOL by chiral phosphoric acid catalyzed asymmetric acylation. PHANOL enantiomers were well differentiated by the chiral environment of chiral phosphoric acid, and both the corresponding monoester and PHANOL were obtained with excellent enantioselectivities (98% ee and 92% ee, respectively). Detailed examination of the substrates suggests that the presence of two hydroxy groups in PHANOL was critical for both reactivity and enantioselectivity.

Reported herein is an enantiodivergent synthesis of chiral biaryls by a chiral phosphoric acid catalyzed asymmetric transfer hydrogenation reaction. Upon treatment of biaryl lactols with aromatic amines and a Hantzsch ester in the presence of chiral phosphoric acid, dynamic kinetic resolution (DKR) involving a reductive amination reaction proceeded smoothly to furnish both R and S isomers of chiral biaryls with excellent enantioselectivities by proper choice of hydroxyaniline derivative. This trend was observed in wide variety of substrates, and various chiral biphenyl and phenyl naphthyl adducts were synthesized with satisfactory enantioselectivities in enantiodivergent fashion. The enantiodivergent synthesis of synthetically challenging, chiral o-tetrasubstituted biaryls were also accomplished, and suggests high synthetic potential of the present method.

Highly diastereoselective synthesis of tricyclic fused-pyrans was achieved by Brønsted acid catalyzed double C(sp3)–H bond functionalization., Described herein is the Brønsted acid-catalyzed double C(sp3)–H bond functionalization of alkyl phenethyl ether derivatives. In this process, a [1,5]-[1,5]-hydride shift occurred successively to afford tricyclic fused pyran derivatives in excellent chemical yields with excellent diastereoselectivities (up to >20 : 1). The key to achieve this reaction was the introduction of two methyl groups at the benzylic position, which was effective in both hydride shift processes: (1) the Thorpe–Ingold effect for the first hydride shift and (2) conformational control in the second hydride shift.

Objectives: According to our previous work, aripiprazole exerted a protective effect on hydrogen peroxide (H2O2)-treated PC12 cells; haloperidol did not. Because aripiprazole has distinct affinities to a set of neurotransmitter receptor subtypes, this study aimed to clarify which subtype is responsible for rescuing cells from 0.25 mM H2O2 exposure. Methods: A set of compounds, which are more specific to each subset of G-protein coupled receptors, were examined for their ability to mimic the pharmacological effects of aripiprazole or haloperidol, including their Ki values. The viability of PC12 cells cultured with test compounds with or without H2O2 was assessed using WST-8 reagent. Results: Results from in vitro studies using PC12 cells showed that agonism at serotonin 5-HT2C-receptors based on the antagonism against 5-HT2B-receptors played a significant role in resistingH2O2-induced cell death. However, the use of a specific 5-HT2B-receptor agonist instead of a 5-HT2B-receptor antagonist completely negated the effect of a specific 5-HT2C-receptor agonist. Furthermore, unlike the dopamine D1-receptor specific antagonist, none of the agonists of dopamine D2-, D3-, and D4-receptors ameliorated the cytopathic effects of H2O2. Conclusion: Antagonism at 5-HT2B-receptors is fundamental for the protection of PC12 cells against the cytopathic effects caused by 0.25 mM H2O2. However, the role of negatively regulated cyclic adenosine monophosphate in this phenomenon requires further investigation.

We report a highly diastereoselective synthesis of 1,3-disubstituted tetralin derivatives via Lewis acid catalyzed benzylic C(sp

We previously showed that aripiprazole increases intracellular NADPH and glucose-6-phosphate dehydrogenase mRNA in PC12 cells. Aripiprazole presumably activates a system that concurrently detoxifies reactive oxygen species and replenishes NADPH. Nrf2, a master transcriptional regulator of redox homeostasis genes, also activates the pentose phosphate pathway, including NADPH production. Therefore, our aim was to determine whether aripiprazole activates Nrf2 in PC12 cells. Aripiprazole increased mRNA expression of Nrf2-dependent genes (NAD(P)H-quinone oxidoreductase-1, Nqo1; heme oxygenase-1, HO1; and glutamate-cysteine ligase catalytic subunit) and protein expression of Nqo1 and HO1 in these cells (p < 0.05). To maintain increased Nrf2 activity, it is necessary to inhibit Nrf2 degradation; this is done by causing Nrf2 to dissociate from Keap1 or β-TrCP. However, in aripiprazole-treated cells, the relative amount of Nrf2 anchored to Keap1 or β-TrCP was unaffected and Nrf2 in the nuclear fraction decreased (p < 0.05). Aripiprazole did not affect phosphorylation of Nrf2 at Ser40 and decreased the relative amount of acetylated Nrf2 (p < 0.05). The increase in Nqo1 and HO1 in aripiprazole-treated cells cannot be explained by the canonical Nrf2-degrading pathways. Further experiments are needed to determine the biochemical mechanisms underlying the aripiprazole-induced increase in these enzymes.

We report herein a highly enantioselective synthesis of multisubstituted biaryl chlorides/iodides by sequential halogenation reactions (desymmetrization/kinetic resolution sequence). The selectivity of biaryl chlorides/iodides obtained in the first asymmetric reaction (desymmetrization) could be enhanced by the kinetic resolution-type asymmetric bromination to afford the corresponding chiral biaryl chlorides/iodides in excellent selectivities (up to 99 % ee).

We previously reported that an optimal dose of lipopolysaccharide (LPS) markedly extends the lifespan of murine primary-cultured microglia by suppressing cell death pathways. In this study, we investigated the effects of LPS pretreatment on UV light-induced apoptosis of cells from the microglial cell line BV-2. More than half of BV-2 cells were apoptotic, and procaspase-3 was cleaved into its active form at 3 h of UV irradiation. In contrast, in BV-2 cells treated with LPS for 24 h, UV irradiation caused neither apoptosis nor procaspase-3 cleavage. LPS treatment arrested the cell cycle in G1 phase and upregulated cyclin-dependent kinase inhibitor p21Waf1/Cip1 and growth arrest and DNA damage-inducible (GADD) 45α in BV-2 cells. When p21Waf1/Cip1 and GADD45α were knocked down by small interfering RNA, procaspase-3 was cleaved into its active form to induce apoptosis. Our findings suggest that LPS inhibits UV-induced apoptosis in BV-2 cells through arrest of the cell cycle in G1 phase by upregulation of p21Waf1/Cip1 and GADD45α. Excessive activation of microglia may play a critical role in the exacerbation of neurodegeneration, therefore, normalizing the precise regulation of apoptosis may be a new strategy to prevent the deterioration caused by neurodegenerative disorders.

We describe herein a chiral phosphoric acid catalyzed Friedel–Crafts reaction of indoles with β-alkoxycarbonyl-β-disubstituted nitroalkenes. A wide variety of substrates participated in this reaction to afford indoles having all-carbon quaternary centers with excellent selectivities (up to 97% ee). Further investigation suggested that the olefin geometry and the employment of NH-indole derivatives are responsible for both reactivity and selectivity.

Described herein is the enantioselective synthesis of multisubstituted biaryl derivatives by chiral phosphoric acid catalyzed asymmetric bromination. Two asymmetric reactions (desymmetrization and kinetic resolution) proceeded successively to afford chiral biaryls in excellent enantioselectivities (up to 99% ee). Both experimental and computational studies suggested that this excellent selectivity could be achieved via a highly organized hydrogen bond network among a substrate, a catalyst (chiral phosphoric acid), and a brominating reagent (N-bromophthalimide).