Divergent total synthesis of penaresidin B and its straight side chain analogue

The divergent synthesis of penaresidin B and its straight side chain analogue was accomplished by constructing an azetidine ring via S_N2 type cyclization of protected 2,3-syn-3,4-syn-4-amino-1,3-dihydroxyhept-6-en-2-yl mesylate and late-stage introduction of an alkyl side chain via olefin cross-metathesis of 4-allylazetidine with readily available terminal alkenes. This synthetic route would be useful to synthesize penaresidin side chain analogues.     

Organic light-emitting transistors with a thin metal layer covering a diffraction grating

We fabricated organic light-emitting transistors (OLETs) characterized by an Ag layer deposited on a one-dimensional (1D) or two-dimensional (2D) diffraction grating that acts as a combined gate insulator with SiO₂. The Ag layer was entirely covered with an organic crystal. Upon photoexcitation that crystal showed narrow linewidth emissions (NLEs) parallel to the substrate plane. The narrowed lines were either redshifted or blueshifted with rotation of the crystal around a normal to its surface with respect to the grating wave vector. Strong emissions (～10⁴–10⁶ cd m^?2) accompanied by current-injected NLEs were observed from the 1D and 2D grating OLETs.     

Convergent Synthesis of (−)‐Quinocarcin Based on the Combination of Sonogashira Coupling and Gold(I)‐Catalyzed 6‐endo‐dig Hydroamination

The total synthesis of the pentacyclic tetrahydroisoquinoline alkaloid quinocarcin, which possesses intriguing structural and biological features, has been achieved through a gold(I)‐catalyzed regioselective hydroamination reaction. It is noteworthy that the regioselectivity of the intramolecular hydroamination of an unsymmetrical alkyne could be completely switched through substrate control. Other key features of this synthesis include the highly stereoselective synthesis of 2,5‐cis‐pyrrolidine through the intramolecular amination of the bromoallene and the Lewis acid mediated ring opening of dihydrobenzofuran.     

Single‐Molecule Visualization of the Activity of a Zn2+‐Dependent DNAzyme

We demonstrate the single‐molecule imaging of the catalytic reaction of a Zn²⁺‐dependent DNAzyme in a DNA origami nanostructure. The single‐molecule catalytic activity of the DNAzyme was examined in the designed nanostructure, a DNA frame. The DNAzyme and a substrate strand attached to two supported dsDNA molecules were assembled in the DNA frame in two different configurations. The reaction was monitored by observing the configurational changes of the incorporated DNA strands in the DNA frame. This configurational changes were clearly observed in accordance with the progress of the reaction. The separation processes of the dsDNA molecules, as induced by the cleavage by the DNAzyme, were directly visualized by high‐speed atomic force microscopy (AFM). This nanostructure‐based AFM imaging technique is suitable for the monitoring of various chemical and biochemical catalytic reactions at the single‐molecule level.