Formation of Supramolecular Nanostructures through in Situ Self-Assembly and Post-Assembly Modification of a Biocatalytically Constructed Dipeptide Hydrazide**

Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.     

Planarized Phenyldithienylboranes: Effects of the Bridging Moieties and π-Extension on the Photophysical Properties and Lewis Acidity

Two kinds of planarized phenyldithienylboranes, which contain (CH₃)₂C- or CH₂-bridging moieties, were synthesized. The difference of the bridging moieties affects their packing structures and photophysical properties. In particular, the (CH₃)₂C-bridged derivative exhibits a large Stokes shift, unusual for such planarized compounds, that results from a large structural relaxation in the excited state. A series of π-extended derivatives was synthesized, among which a p-(diphenylamino)phenyl-substituted derivative shows large solvatochromism in the fluorescence spectra, while maintaining high quantum yields even in polar solvents. The Lewis acidity of the phenyldithienylborane derivatives was also assessed by titration with pyridine. The Lewis acidity of the boron center is affected not only by the difference in the steric bulk of the bridging moieties, but also by the electronic effect of the substituents introduced at remote positions relative to the boron atom. These results demonstrate the characteristic features of planarized phenyldithienylboranes as building blocks for boron-based π-electron materials.     

Divergent and Chemoselective Transformations of Thioamides with Designed Carbene Equivalents

The reactions of thioamides with ortho-nitro-substituted iodonium ylides proceeded under mild conditions to give enaminones or thiazoles, depending on the iodonium ylide used. This protocol allowed the use of protic solvents, including aqueous solutions, and therefore coupling reactions with complex molecules such as peptides or steroids were possible. A mild and efficient method for the synthesis of various iodonium ylides was established. DFT calculations suggested that the halogen bonding between a thioamide and iodonium ylide was important in this chemoselective coupling reaction. The potential use of enaminones conjugated with pharmaceuticals as prodrugs was also demonstrated.     

Total Synthesis of Terpioside B

The first total synthesis of terpioside B ( 1 ) has been accomplished. Key steps include the stereoselective installments of a set of challenging 1,2-cis-glycosidic linkages. Thus, α(1,4)-linked d -galactoside was effectively constructed from a 1,2-anhydrogalactose donor and an unprotected 1,6-anhydrogalactose acceptor by using a boron-mediated aglycon delivery (BMAD) method. In addition, α-l -fucofuranosides were stereoselectively and simultaneously constructed by remote group-assisted 1,2-cis-α-stereoselective glycosylations.     

Anionic ring-opening polymerization behavior of trans-cyclohexene carbonate using metal tert-butoxides: Construction of living anionic ring-opening polymerization by lithium tert-butoxide

Anionic ring-opening polymerization (ROP) behavior of trans-cyclohexene carbonate (CHC) using metal alkoxides as initiators was investigated. As a result, lithium tert-butoxide-initiated ROP of CHC with a high-monomer concentration (10 M) at low temperature (−15 to −10°C) proceeded to afford a poly(trans-cyclohexene carbonate) (PCHC) without undesired side reactions such as mainly backbiting. The suppression of side reactions enables the control of the molecular weight (M_n = 2400–6100) of PCHC with low molar-mass dispersity values (M_w/M_n = 1.16–1.22). Furthermore, by increasing the feed ratio of the monomer to the initiator, the molecular weight increases proportionally, indicating a controllable polymerization. The results of a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis, a kinetic study, and a chain extension experiment suggested a living nature of this ROP using lithium tert-butoxide.     

A Strategy to Control the Reactivation of Frustrated Lewis Pairs from Shelf‐Stable Carbene Borane Complexes

N‐Phosphine oxide substituted imidazolylidenes (PoxIms) have been synthesized and fully characterized. These species can undergo significant changes to the spatial environment surrounding their carbene center through rotation of the phosphine oxide moiety. Either classical Lewis adducts (CLAs) or frustrated Lewis pairs (FLPs) are thus formed with B(C₆F₅)₃ depending on the orientation of the phosphine oxide group. A strategy to reactivate FLPs from CLAs by exploiting molecular motions that are responsive to external stimuli has therefore been developed. The reactivation conditions were successfully controlled by tuning the strain in the PoxIm–B(C₆F₅)₃ complexes so that reactivation only occurred above ambient temperature.     

Conformational and Intermolecular Interaction Dynamics of Photolyase/Cryptochrome Proteins Monitored by the Time‐Resolved Diffusion Technique

Cryptochrome (CRY), a blue light sensor protein, possesses a similar domain structure to photolyase (PHR) that, upon absorption of light, repairs DNA damage. In this review, we compare the reaction dynamics of these systems by monitoring the reaction kinetics of conformational change and intermolecular interaction change based on time‐dependent diffusion coefficient measurements obtained by using the pulsed laser‐induced transient grating technique. Using this method, time‐dependent biomolecular interactions, such as transient dissociation reactions in solution, have been successfully detected in real time. Conformational change in (6‐4) PHR has not been detected after the photoexcitation by monitoring the diffusion coefficient. However, the repaired DNA dissociates from PHR with a time constant of 50 μs, which must relate to a minor conformational change. However, CRY exhibits a considerable diffusion change with a time constant of 400 ms, which indicates that the protein–solvent interaction is changed by the conformational change. The C‐terminal domain of CRY is shown to be responsible for this change.     

Conductive liquid crystalline compounds having a piperazine structure

New conductive thermotropic liquid crystalline materials having a piperazine ring in the central core: 1-[4-(9-decenyloxy)phenyl]-4-alkylpiperazines (6) were synthesized. The mesomorphic behaviours of these compounds and their conductivity in the liquid crystal phase were measured. The principal features of these compounds are to exhibit a smectic B phase around room temperature (for example 6: Cr 50 SmB 81 I, °C) and to exhibit a large dark current (6d: 430 μA cm^?2, applied voltage 20 V, at 70°C) in the smectic B phase.     

Microwave-Accelerated Selective Acylation of (Hydroxyalkyl)phenols Using Acid Chlorides

Highly selective acylation of the alcoholic hydroxy group can be achieved with (hydroxyalkyl)phenols carrying both alcoholic and phenolic hydroxyls by the use of the most common acylating agents, acid chlorides, under microwave irradiation.