Masaki Nishijima

Herein, a comprehensive kinetic study is performed to compare the catalytic efficiency of 2-azaadamantane N-oxyl (AZADO) derivatives with that of 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) used as radical catalysts in the aerobic oxidation of l-menthol. Furthermore, the correlation between the catalytic activity and structural/electronic parameters of AZADOs and TEMPO is elucidated. The reaction rate constants achieved with several AZADO derivatives exhibit moderate relationships with spectroscopic parameters, such as the hyperfine coupling constant of the N atom (A_N) and NO stretching vibration frequency (ν_NO) observed in electron spin resonance and infrared spectra, respectively. The planarity C-(NO)-C angle (φ) at the N atom, determined by density functional theory (DFT) calculations, also strongly correlates with the A_N and ν_NO. Moreover, the bond order of NO, which strongly depends on the structural and electronic properties of NO radicals, correlates with radical activity; thus, the radical activity can be predicted by DFT calculations, thereby accelerating the synthesis of new AZADO derivatives without requiring alcohol oxidation experiments.

Near perfect head-to-head selectivity upon supramolecular [4+4] photocyclodimerisation of 2-anthracenecarboxylate were achieved through silicificated self-organised gemini surfactant bilayers in water at room temperature.

We synthesized N-benzoyl-protected peptide nucleic acid (PNA) monomers, which are robust under the condition for deprotecting 9-fluorenylmethoxycarbonyl (Fmoc) group by piperidine but are removable by aqueous ammonia and hence totally compatible with the Fmoc-solid phase synthesis. This new invention expands the range of available nucleobase sequences, allowing us to use acid-sensitive PNA oligomers and purine nucleotides (both of which are difficult to use in the conventional methods) in the preparation of PNA-DNA chimeras to avoid the drawbacks of traditional PNAs.

The synthesis and optical properties of 1,8‐diphenyl‐9,10‐bis(arylethynyl)phenanthrenes, which are distorted phenanthrenes, are reported. The presence of the two phenyl groups at the 1,8‐positions of phenanthrene significantly distorts the molecular geometries, as was evidenced by X‐ray crystallography. The congested substitution pattern in the K region results in a distorted aromatic framework, which leads to a redshift in the emission spectrum. These observations are in stark contrast to 9,10‐bis(phenylethynyl)phenanthrene with no phenyl groups at the 1,8‐positions. A large Stokes shift suggested extensive structural relaxation between the phenyl and arylethynyl units in the excited state, which was supported by theoretical calculations.

Intracellular delivery is crucial not only in achieving effective oligonucleotide therapeutics but also for a wide variety of therapeutic strategies. In this study to elucidate the effects of the number of incorporated arginine residues on cell membrane permeability, we designed a series of peptide ribonucleic acids (PRNAs) that alternatingly incorporated 4, 8, or 12 arginine residues (P_RR1-3) in the PRNA backbone for experimental verifications. Indeed, the cellular uptake efficiency and the aggregation properties turned out to be critical functions of the number of incorporated arginine residues. Thus, the optimized P_RR2 that incorporates 8 arginines showed the most efficient cellular uptake ability, much higher than that of octaarginine, without accompanying cytotoxicity or aggregation.

Chiral slipped 5,8:9',10'-cyclodimers were preferentially produced over classical 9,10:9',10'-cyclodimers upon supramolecular photocyclodimerization of 2-anthracenecarboxylate (AC) mediated by β-cyclodextrin (β-CD). This photochirogenic route to the slipped cyclodimers, exclusively head-to-tail (HT) and highly enantioselective, has long been overlooked in foregoing studies but is dominant in reality and is absolutely supramolecularly activated by 2:2 complexation of AC with β-CD. The intricate structural and photophysical aspects of this higher-order complexation-triggered process were comprehensively elucidated, while the absolute configurations of the slipped cyclodimers were unambiguously assigned by comparing the experimental versus theoretical circular dichroism spectra. In the 2:2 complex, two ACs packed in a dual -CD capsule are not fully overlapped with each other but only partially stacked in slipped anti- or syn-HT manner, and hence do not spontaneously cyclodimerize upon photoexcitation but emits long-lived excimer fluorescence at wavelengths slightly longer than the monomer fluorescence, indicating that the slipped excimer is neither extremely reactive nor completely relaxed in conformation and energy. Due to the slipped conformation of the AC pair in soft capsule, the subsequent photocyclodimerization becomes manipulable by various internal/external factors, such as temperature, pressure, added salt, and host modification, enabling us to exclusively obtain the slipped cyclodimers in high regio- and enantioselectivities. In this supramolecularly driven photochirogenesis, the dual β-CD capsule functions as a chiral organophotocatalyst to trigger and accelerate the nonclassical photochirogenic route to slipped cyclodimers by pre-organizing the conformation of encapsulated AC pair, formally mimicking catalytic antibody.

Proteins in solution are conventionally considered macromolecules. Dynamic microscopic structures in supersaturated protein solutions have received increasing attention in the study of protein crystallisation and the formation of misfolded aggregates. Here, we present a method for observing rotational dynamic structures that can detect the interaction of nanoscale lysozyme protein networks via diffracted X-ray tracking (DXT). Our DXT analysis demonstrated that the rearrangement behaviours of lysozyme networks or clusters, which are driven by local density and concentration fluctuations, generate force fields on the femtonewton to attonewton (fN – aN) scale. This quantitative parameter was previously observed in our experiments on supersaturated inorganic solutions. This commonality provides a way to clarify the solution structures of a variety of supersaturated solutions as well as to control nucleation and crystallisation in supersaturated solutions.

Molecularly imprinted cavities have functioned as a regioselective reaction field for the [4 + 4] photocyclodimerization of 2-anthracenecarboxylic acid (2-AC). Molecularly imprinted polymers were prepared by precipitation polymerization of N-methacryloyl-4-aminobenzamidine as a functional monomer to form a complex with template 2-AC and ethylene glycol dimethacrylate as a crosslinking monomer. The 2-AC-imprinted cavities thus constructed preferentially bound 2-AC with an affinity greater than that toward structurally related 9-anthracenecarboxylic acid, 2-aminoanthracene, and unsubstituted anthracene. Moreover, from the four possible regioisomeric cyclodimers, they mediated the [4 + 4] photocyclodimerization of 2-AC specifically to the anti-head-to-tail (anti-HT) isomer. This indicates that the imprinted cavities accommodate two 2-AC molecules in an anti-HT manner, thereby facilitating the subsequent regioselective photocyclodimerization.