Synthesis of a cyclic peptide/protein using the NEXT-A reaction followed by cyclization

By using the NEXT-A reaction, we introduced a non-natural amino acid at the N-terminus of a peptide/protein that contained a cysteine unit. The side chain of the introduced amino acid spontaneously reacted with the cysteine to afford a cyclic peptide/protein.     

Preparation of tannin gel by enzyme-mimetic reaction of condensed tannin without use of crosslinking agent

Preparation of tannin gels was attempted by means of enzyme-mimetic reaction of condensed tannin without use of crosslinking agent. The gelation of condensed tannin was performed in the presence of H₂O₂ catalyzed by hematin of a ferriprotoporphyrin complex in water. The compressive measurements of the gels obtained by the 30–50 wt% concentrations of the tannin using 0.20–0.50 ml of 30 w/v% H₂O₂ aq. were examined. There is a tendency for the compressive properties of the gels obtained from the higher concentrations of the tannin and the larger amounts of H₂O₂ to be superior. The obtained gel was characterized by means of IR spectroscopy. Moreover, the obtained tannin gel was compatibilized with natural rubber to form a composite material.     

Construction of Quaternary Carbon Center by Catalytic Asymmetric Alkylation of 3‐Arylpiperidin‐2‐ones Under Phase‐Transfer Conditions

A highly enantioselective synthesis of δ‐lactams having a chiral quaternary carbon center at the α‐position has been developed through an asymmetric alkylation of 3‐arylpiperidin‐2‐ones under phase‐transfer conditions. In this transformation, a 2,2‐diarylvinyl group on the δ‐lactam nitrogen atom plays a crucial role as a novel protecting group and an achiral auxiliary for improving both yield and enantioselectivity of the reaction.     

Photoinduced Endosomal Escape Mechanism: A View from Photochemical Internalization Mediated by CPP-Photosensitizer Conjugates

Endosomal escape in cell-penetrating peptide (CPP)-based drug/macromolecule delivery systems is frequently insufficient. The CPP-fused molecules tend to remain trapped inside endosomes and end up being degraded rather than delivered into the cytosol. One of the methods for endosomal escape of CPP-fused molecules is photochemical internalization (PCI), which is based on the use of light and a photosensitizer and relies on photoinduced endosomal membrane destabilization to release the cargo molecule. Currently, it remains unclear how this delivery strategy behaves after photostimulation. Recent findings, including our studies using CPP-cargo-photosensitizer conjugates, have shed light on the photoinduced endosomal escape mechanism. In this review, we discuss the structural design of CPP-photosensitizer and CPP-cargo-photosensitizer conjugates, and the PCI mechanism underlying their application.     

A guanine-substituted nitronyl nitroxide radical forming a one-dimensional ferromagnetic chain

A stable guanine-substituted nitronyl nitroxide radical 1 has been synthesized and characterized. The single-crystal structure analyses and magnetic susceptibility measurements exhibit a one-dimensional architecture of guanine base resulting from carbonyl-amino hydrogen bonds in the solid state, giving a 1D ferromagnetic chain of the radical moieties.     

Zwitterionic pi-radical involving EDT-TTF-imidazole and F4TCNQ: redox properties and self-assembled structure by hydrogen-bonds and multiple S...S interactions

The reaction between an imidazole-functionalized EDT-TTF and F(4)TCNQ produced a zwitterionic pi-radical, which formed a self-assembled structure by the cooperation of hydrogen-bonds and multiple S...S interactions and exhibited three-step oxidation processes and a high electrical conductivity as a single-component organic molecule.     

Synthesis and properties of 3-arylcyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-diones and related compounds: photo-induced autorecycling oxidation of some amines

Novel 3-phenyl- and 3-(4-nitrophenyl)cyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-diones and the corresponding imino derivatives 5a,b and 6a,b were synthesized in modest to moderate yields by the abnormal and normal aza-Wittig reaction of 2-(1,3-diazaazulen-2-ylimino)triphenylphosphorane with aryl isocyanates and subsequent heterocyclization reaction with a second isocyanate. The related cationic compound, 1-methyl-3-phenylcyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-dionylium tetrafluoroborate 7a, was also prepared. The electrochemical reduction of these compounds exhibited more positive reduction potentials as compared with those of the related compounds of 3,10-disubstituted cyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1H,3H)-dione systems. In a search of the oxidizing ability, compounds 5a, 6a, and 7a were demonstrated to oxidize some amines to give the corresponding imines in more than 100% yield under aerobic and photo-irradiation conditions, while even benzylamine was not oxidized under aerobic and thermal conditions at 100 °C. The oxidation reactions by cation 7a are more efficient than that by 5a and 6a. Quenching of the fluorescence of 5a was observed, and thus, the oxidation reaction by 5a probably proceeds via electron-transfer from amine to the excited singlet state of 5a. In the case of cation 7a, the oxidation reaction is proposed to proceed via formation of an amine-adduct of 7a and subsequent photo-induced radical cleavage reaction.     

Quinolizinium hexafluorophosphate

The crystal structure of the title compound, C₉H₈N⁺·PF₆⁻, was measured at 145 K. The cationic part of the compound has crystallographically imposed 2/m symmetry with N/C disorder.     

Spin-polarization in a 3-terminal conductor induced by Rashba spin–orbit coupling

We investigate numerically the spin polarization of the current in the presence of Rashba spin–orbit interaction (RSOI) in a 3-terminal conductor. We use equation-of-motion method to simulate the time evolution of the wave packet and focus on single-channel transport. A T-shaped conductor with uniform RSOI proposed by Kiselev and Kim and a Y-shaped conductor with nonuniform RSOI are considered. In the T-shaped conductor, the strength of RSOI is assumed to be uniform. We have found that the spin polarization becomes nearly 100% with little loss of conductance for sufficiently strong spin–orbit coupling. This is due to the spin-dependent group velocity of electrons at the junction which causes the spin separation. In the Y-shaped conductor, the strength of RSOI is modulated perpendicular to the charge current. A spatial gradient of effective magnetic field due to the nonuniform RSOI causes the Stern–Gerlach type spin separation. The direction of the polarization is perpendicular to the current and parallel to the spatial gradient. Again almost 100% spin polarization can be realized by this spin separation.     

Synthetic study of manzamine B: synthesis of the tricyclic central core by an asymmetric Diels-Alder and RCM strategy

Tricyclic core of manzamine B was successfully synthesized through asymmetric Diels-Alder reaction and RCM strategy. Cr-salen-F complex was found to be the most effective catalyst in DA reaction of aminodienes with heterocyclic dienophiles to give up to 97% ee. In the construction of 11-membered ring by RCM, first-Grubbs cat. gave better stereoselectivity.