General Synthesis of meso-1,4-Dialdehydes and Their Application in Ir-Catalyzed Asymmetric Tishchenko Reactions.

A practical synthesis of meso-1,4-dialdehydes based on the oxidative cleavage of cyclobutanediol derivatives using polymer-supported periodate was developed. The meso-1,4-dialdehydes were obtained in up to >99% yield and subsequently employed in Ir-catalyzed asymmetric Tishchenko reactions to give the corresponding chiral lactones, which are versatile synthetic intermediates, in good yield with moderate enantiomeric excess. The catalytically active species was identified by means of cold-spray ionization mass spectrometry and 1H NMR spectroscopy.

Axially Chiral Borinic Acid Catalysts: Design, Synthesis, and Application in Alkylative Desymmetrization of 1,2-Diols.

A novel chiral borinic acid (CBA), an organocatalyst possessing a binaphthyl skeleton, was designed and synthesized. The synthesis of CBA was achieved with a 72% yield in four steps starting with optically pure 1,1'-bi-2-naphthol. The asymmetric catalytic activity was investigated in the desymmetrization of meso-1,2-diol.

Accumulation of squalene in filamentous fungi Trichoderma virens PS1-7 in the presence of butenafine hydrochloride, squalene epoxidase inhibitor: biosynthesis of 13C-enriched squalene.

Squalene is a triterpenoid compound and widely used in various industries such as medicine and cosmetics due to its strong antioxidant and anticancer properties. The purpose of this study is to increase the accumulation of squalene in filamentous fungi using exogeneous butenafine hydrochloride, which is an inhibitor for squalene epoxidase. The detailed settings achieved that the filamentous fungi, Trichoderma virens PS1-7, produced squalene up to 429.93 ± 51.60 mg/L after culturing for 7 days in the medium consisting of potato infusion with glucose at pH 4.0, in the presence of 200 µm butenafine. On the other hand, no squalene accumulation was observed without butenafine. This result indicated that squalene was biosynthesized in the filamentous fungi PS1-7, which can be used as a novel source of squalene. In addition, we successfully obtained highly 13C-enriched squalene by using [U-13C6]-glucose as a carbon source replacing normal glucose.

Photoluminescent supramolecular gels derived from phenylenediamine hydrochlorides.

Supramolecular gels are promising as chemosensors, drug delivery systems and oil gelators. The present paper deals with photoluminescent supramolecular gels derived from phenylenediamine hydrochlorides. N-(3,5-Diaminobenzoyl)-L-alanine dodecyl ester dihydrochlorides (1L) underwent gelation in tetrahydrofuran (THF) and CHCl3, but not in C1-C4 alcohols, dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). Compound 1L emitted blue fluorescence in the sol state and green fluorescence in the gel state. A THF solution of 1L exhibited absorption and emission maxima at wavelengths 94-104 nm and 92-110 nm longer than those in other solvents, such as methanol and ethanol, that cause no gelation of 1L. Particles with hydrodynamic diameters around 13 nm were detected in a THF solution (c = 1.0 mM) of 1L. The gelation of 1L in THF and CHCl3, and the lack of gelation in MeOH were supported by molecular dynamics simulations and dynamic light scattering measurements. N-(3,5-Diaminobenzoyl)-L-alanine dodecyl ester (1L'), an HCl-free analogous compound of 1L, underwent no gelation in THF and CHCl3, indicating the necessity of the ammonium salt structure for gelation. The UV-vis absorption and photoluminescence spectroscopic peaks of 1L red-shifted upon aggregation, which was supported by TD-DFT calculations of monomeric and dimeric models of 1L.

Development of Cycloisomerization with Rearrangement of a Tosyl Group Using N-Tosyl-o-allenylaniline.

Sulfonyl indoles were synthesized by migratory cycloisomerization from the allene N-tosyl-o-allenylaniline. 3-Tosyl indoles or 4-tosyl indoles were selectively produced using a Pd catalyst or a Au catalyst, respectively.

Design and synthesis of 4-acetoxypentanamide derivatives of spliceostatin A and their biological evaluation towards prostate cancer treatment.

We designed and synthesized novel 4-acetoxypentanamide derivatives of spliceostatin A, whose 4-acetoxypentenamide moiety is reduced (7), isomerized (8), or substituted with methyl at the α-position (9). The results of biological evaluation against AR-V7 and the docking analysis of each derivative suggest that the geometry of the 4-acetoxypentenamide moiety of spliceostatin A is important for its biological activity.

Enantioselective Construction of Consecutive Tetrasubstituted Stereogenic Centers by Reaction of α-Substituted ß-Nitroacrylates with Oxazol-5-(4H)-ones Catalyzed by Cinchona Alkaloid Sulfonamide Catalysts.

The enantioselective reaction of α-substituted ß-nitroacrylates with oxazol-5-(4H)-ones (oxazolones) to construct consecutive tetrasubstituted stereogenic centers was accomplished. A cinchona alkaloid sulfonamide catalyst afforded products bearing vicinal chiral centers with excellent enantio- and diastereoselectivities. The obtained products were successively converted into various chiral compounds without loss of their enantiopurity. Furthermore, density functional theory (DFT) calculations were performed to elucidate the mechanism and origin of the observed stereoselectivity of the reaction.

Synthesis of a platinacycle: determination of the structure and examination of the photophysical properties based on DFT calculations.

Platinum-containing macrocycles (platinacycles) have gained attention due to their unique photoelectric properties. In the present study, a novel conjugated platinacycle was synthesized by the dehydrochlorination coupling reaction of a bipyridine dichloroplatinum(II) complex and a 3,6-diethynylcarbazol derivative. The structure of the platinacycle was confirmed by 1H/13C, 1H-1H COSY, HMQC, HMBC, DEPT NMR spectroscopies in conjunction with DFT calculations, IR spectroscopy and MALDI-TOF mass spectrometry. The platinacycle exhibited a UV-vis absorption around 540 nm assignable to ligand-ligand charge transfer, and birefringence in DMF, possibly due to alignment of molecules.

Direct Catalytic Enantioselective Reaction of α-Isocyanoacetonitriles with Ketimines Using Cinchona Alkaloid Amide-Cu(II) Catalysts.

The first enantioselective reaction of α-isocyanoacetonitriles was developed. The reaction of various α-isocyanoacetonitriles with ketimines using cinchona alkaloid amide-Cu(II) catalysts afforded imidazolines with consecutive tetrasubstituted stereogenic carbon centers in good yields and high diastereo- and enantioselectivities. The stereoselectivity of the reaction is explained on the basis of the control experiment and density functional theory (DFT) calculations. The products were subsequently converted into chiral compounds. This process highlights the possible use of α-isocyanoacetonitriles for asymmetric and organic syntheses.

Reagent-Controlled Regioselective Intramolecular [2+2] Cycloaddition between Vinylsilanes and Allenes.

This paper provides the first report of the intramolecular [2+2] cycloaddition of vinylsilane. The [2+2] cycloaddition of allenes is a useful reaction that can synthesize cyclobutanes. However, no previous works have attempted to control the regioselectivity between the two double bonds of allenes only by changing the reaction conditions, although there have been some reports of the regioselective [2+2] cycloaddition of allenes by changing the substrate. In this study, we have succeeded in controlling intramolecular [2+2] cycloaddition reactions at the proximal and distal positions of allenes simply by changing the reaction conditions. We found that the atomic radius of silicon is very important for perfect control of the reaction's sites. The structures of all key compounds were determined by the crystal sponge method which could identify the structures of liquid compounds.

Enantioselective Reaction of N-Unprotected Activated Ketimines with Phosphine Oxides Catalyzed by Chiral Imidazoline-Phosphoric Acids.

The first enantioselective hydrophosphonylation of ketimines with phosphine oxides was developed. The reaction of unprotected ketimines with phosphine oxides using a bis(imidazoline)-phosphoric acid catalyst gave chiral α-quaternary aminophosphorous compounds having a primary amino group in excellent yields and enantioselectivities. Based on experimental results and DFT calculation, transition states were proposed to explain the stereoselectivity of the reaction.

Dimethylacetamide-stabilized ruthenium nanoparticles for catalysing α-alkylations of amides with alcohols.

α-Alkylation reactions between amides and alcohols, with dimethylacetamide-stabilized Ru nanoparticles (NPs) as the catalyst, were investigated. The reactions proceeded with low catalyst loadings compared to metal complexes. Characterizations of the Ru NPs were performed by X-ray photoelectron spectroscopy, X-ray absorption fine structure spectroscopy, and various techniques. Control experiments revealed the reaction mechanisms, which proceeded via hydrogen autotransfer with alcohols.

DAST-mediated ring-opening of cyclopropyl silyl ethers in nitriles: facile synthesis of allylic amides via a Ritter-type process.

A diethylaminosulfur trifluoride (DAST)-mediated ring-opening reaction of cyclopropyl silyl ethers in nitriles produced allylic amides in moderate to good yields (up to 87%). Time course studies using ReactIR and O-isotopic labeling mechanistic studies suggested that the present reaction occurs via a Ritter-type process, leading to the formation of allylic amides.

N,N-Dimethylformamide-stabilized ruthenium nanoparticle catalyst for ß-alkylated dimer alcohol formation via Guerbet reaction of primary alcohols.

N,N-Dimethylformamide-stabilized Ru nanoparticles (NPs) provide a highly efficient catalyst for the Guerbet reaction of primary alcohols. DMF-modified Ru NPs were synthesized, and characterized by transition electron microscopy, and X-ray absorption spectroscopy, X-ray photoelectronspectroscopy, and Fourier-transform infrared spectroscopy. The Ru NP catalyst was highly durable during catalytic reactions under external additive/solvent-free conditions.

Using α- and ß-Epimerizations of cis-2,3-Bis(hydroxymethyl)-γ-butyrolactone for the Synthesis of Both Enantiomers of Enterolactone.

In the context of asymmetric synthesis, epimerization is usually problematic. Here, we describe the use of the epimerization of cis-2,3-bis(hydroxymethyl)-γ-butyrolactone for the synthesis of enterolactones with anti-carcinogenic, anti-inflammatory, anti-angiogenic, and antioxidant activity. Selective α- or ß-epimerization of a γ-butyrolactone was used to selectively synthesize both enantiomers of enterolactone. Theoretical and kinetic studies were performed to elucidate the epimerization mechanism.

Enantioselective Pictet-Spengler Reaction of Acyclic α-Ketoesters Using Chiral Imidazoline-Phosphoric Acid Catalysts.

The first enantioselective Pictet-Spengler reaction of acyclic α-ketoesters with tryptamines has been developed. Excellent yields and enantioselectivity were obtained for the reaction using chiral imidazoline-phosphoric acid catalysts. Density functional theory calculations suggested possible transition states that explain the origin of chiral induction. This process provides an efficient route for the synthesis of tetrahydro-ß-carboline derivatives.

Double isomerization/cycloisomerization/aromatization of 1-(allyloxy)-2-(cyclopropylmethyl)benzenes to give 2-ethyl-3-isopropylbenzofurans using a multitasking single rhodium catalyst.

Multitasking single-catalyst systems that allow multiple chemical transformations within a single reaction vessel are important for the development of eco-compatible chemistry. Here, we have developed a rhodium-catalyzed system that transforms 1-(allyloxy)-2-(cyclopropylmethyl)benzene derivatives to 2-ethyl-3-isopropylbenzofurans via double isomerization/cycloisomerization/aromatization.

Asymmetric synthesis of tetrasubstituted cyclic amines via aza-Henry reaction using cinchona alkaloid sulfonamide/zinc(II) catalysts.

The first enantioselective aza-Henry reaction of non-activated cyclic iminoesters, derived from cyclic amino acids, has been developed. Good yields and enantioselectivities were observed for the reaction using our original cinchona alkaloid sulfonamide/zinc(II) catalyst. The transition state was proposed to explain the stereoselectivity based on experiments and DFT calculations.

Iridium-Catalyzed Isomerization/Cycloisomerization/Aromatization of N-Allyl-N-sulfonyl-o-(λ1-silylethynyl)aniline Derivatives to Give Substituted Indole Derivatives.

We have developed a one-iridium-catalyst system that transforms N-allyl-N-sulfonyl-2-(silylalkynyl)aniline derivatives, which are 1,7-enynes in which both multiple bonds have a heteroatom, to the corresponding substituted indole derivatives via isomerization/cycloisomerization/aromatization. This strategy provides an atom-economical and straightforward synthetic approach to a series of valuable indoles having vinyl and silylmethyl groups at the 2- and 3-positions.

Cross ß-arylmethylation of alcohols catalysed by recyclable Ti-Pd alloys not requiring pre-activation.

Ti-Pd alloy catalysts were developed for the cross ß-arylmethylation between arylmethylalcohols and different primary alcohols via a hydrogen autotransfer mechanism. The alloy catalysts could be reused multiple times without the need for pre-activation. Analysis of the reaction solution by inductively coupled plasma atomic absorption spectroscopy indicated that only a minimal amount of Ti and no Pd was leached from the catalyst.