A Formal Total Synthesis of Taxol Aided by an Automated Synthesizer

A 36‐step synthesis was carried out in automated synthesizers to provide a synthetic key intermediate of taxol. A key step involved a microwave‐assisted alkylation reaction to construct the ABC ring system from an AC precursor. Subsequent formation of the D ring afforded baccatin III, a well‐known precursor of taxol.     

Shimalactone Biosynthesis Involves Spontaneous Double Bicyclo‐Ring Formation with 8π‐6π Electrocyclization

Shimalactones A and B are neuritogenic polyketides possessing characteristic oxabicyclo[2.2.1]heptane and bicyclo[4.2.0]octadiene ring systems that are produced by the marine fungus Emericella variecolor GF10. We identified a candidate biosynthetic gene cluster and conducted heterologous expression analysis. Expression of ShmA polyketide synthase in Aspergillus oryzae resulted in the production of preshimalactone. Aspergillus oryzae and Saccharomyces cerevisiae transformants expressing ShmA and ShmB produced shimalactones A and B, thus suggesting that the double bicyclo‐ring formation reactions proceed non‐enzymatically from preshimalactone epoxide. DFT calculations strongly support the idea that oxabicyclo‐ring formation and 8π‐6π electrocyclization proceed spontaneously after opening of the preshimalactone epoxide ring through protonation. We confirmed the formation of preshimalactone epoxide in vitro, followed by its non‐enzymatic conversion to shimalactones in the dark.     

Detection of H2O2 released from TiO2 photocatalyst to air.

H2O2 generated and released from TiO2 photocatalysts to the gas phase was detected. A flow-through cell packed with TiO2-coated glass beads was irradiated with UV light, and the gas flowing out of the cell was flushed through a collecting solution containing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulforic acid) diammonium salt (ABTS) and peroxidase. Oxidative coloration of ABTS was observed only in the absence of catalase, indicating the presence of H2O2 in the gas. The quantum yield of the H2O2 generation was estimated to be > 1 x 10(-7). The detected amount of H2O2 decreased as the TiO2 thickness decreased. H2O2 was not detected when dry air or nitrogen was used.     

Rhodium-complex-catalyzed addition reactions of chloroacetyl chlorides to alkynes

The addition reaction of chloroacetyl chloride derivatives with terminal alkynes was found to be catalyzed by Rh(acac)(CO)(AsPh(3)) to afford (Z)-1,4-dichloro-3-buten-2-one derivatives, which displayed diverse reactivities in synthetic elaboration.     

Imidazole‐type thermal latent curing agents with high miscibility for one‐component epoxy thermosetting resins

Epoxy resins are important thermosetting resins widely employed in industrial fields. Although the epoxy–imidazole curing system has attracted attention because of its reactivity, solidification of a liquid epoxy resin containing imidazoles proceeds gradually even at room temperature. This makes it difficult to use them for one‐component epoxy resin materials. Though powder‐type latent curing agents have been used for one‐component epoxy resin materials, they are difficult to apply for fabrication of fine industrial products due to their poor miscibility. To overcome this situation and to improve the shelf life of epoxy–imidazole compositions, we have developed a liquid‐type thermal latent curing agent 1 , generating an imidazole with a thermal trigger via a retro‐Michael addition reaction. The latent curing agent 1 has superior miscibility toward epoxy resins; in addition, it was confirmed that the epoxy resin composition has both high reactivity at 150 °C, and long‐term storage stability at room temperature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2680–2688     

π‐Electron Systems That Form Planar and Interlocked Anion Complexes and Their Ion‐Pairing Assemblies

Interactions between designed charged species are important for the ordered arrangements of π‐electron systems in assembled structures. As precursors of π‐electron anion units, new arylethynyl‐substituted dipyrrolyldiketone boron complexes, which showed anion‐responsive behavior, were synthesized. They formed a variety of receptor–anion complexes ([1+1] and [2+1] types) in solution, and the stabilities of these complexes were discussed in terms of their thermodynamic parameters. Solid‐state ion‐pairing assemblies of [1+1]‐ and [2+1]‐type complexes with countercations were also revealed by single‐crystal X‐ray analysis. In particular, a totally charge‐segregated assembly was constructed based on negatively and positively charged layers fabricated from [2+1]‐type receptor–anion complexes and tetrabutylammonium cations, respectively. Furthermore, the [1+1]‐type anion complex of the receptor possessing long alkyl chains exhibited mesophases based on columnar assembled structures with contributions from charge‐by‐charge and charge‐segregated arrangements, which exhibited charge‐carrier transporting properties.     

One-Pot, Three-Component Coupling Approach to the Synthesis of α-Iminocarboxamides

A one-pot, three-component coupling was accomplished via the nucleophilic addition of an alkylsamarium(III) species to isocyanides and the subsequent addition of the resultant imidoyl samarium(III) species to isocyanates under mild conditions for the formation of α-iminocarboxamides. The developed sequential C-C bond-forming procedure enabled the rapid synthesis of the α-iminocarboxamides in good to excellent yields from readily available starting materials.     

Identification of mutaprodenafil in a dietary supplement and its subsequent synthesis

We isolated a new illegal sildenafil analogue named mutaprodenafil from a dietary supplement for erectile dysfunction (ED) and proposed that it is an aildenafil derivative containing an imidazole moiety. We subsequently synthesized mutaprodenafil from a thioaildenafil and authenticated its structure.     

An iterative approach to the synthesis of thiophene-based organic dyes

We developed an iterative synthetic method for oligo-aryl compounds using an organosilicon-based palladium-catalyzed cross-coupling reaction. Aryl compounds containing a benzyloxy(diisopropyl)silyl group (masked Si group) had sufficient chemical stability, and the unmasking step proceeded in a high yield under mild conditions. Both of the key unmasking/coupling steps required no strict anhydrous or degassed conditions. The developed procedure was used for the synthesis of thiophene-based organic dyes for dye-sensitized solar cells.