Convenient primary amidation of N-protected phenylglycine and dipeptides without racemization or epimerization

Primary amidation of N-protected phenylglycine and dipeptide proceeded easily to afford the corresponding amides in 57–95% yields with 99% ee and 81–99% de, respectively. The procedure is very easy to avoid racemization and epimerization of the products in the reactions by keeping exactly the reaction temperature at −15 °C when the activation of carboxylic acids, followed by the reaction of the mixed carbonic carboxylic anhydride with NH₄Cl.     

Creation of Circularly Polarized Luminescence from an Achiral Polyfluorene Derivative through Complexation with Helix‐Forming Polysaccharides: Importance of the meta‐Linkage Chain for Helix Formation

A circularly polarized luminescence (CPL) material has been created by polymer–polymer complexation between a helix‐forming polysaccharide, schizophyllan (SPG), and a meta‐phenylene‐linked polyfluorene derivative (mPFS). Computational modeling revealed that mPFS can adopt a helical structure although a conventional polyfluorene derivative with a para‐phenylene linkage tends to enjoy a rigid rodlike conformation. Our detailed experimental examination showed that mPFS forms a chiral nanowire complex through cohelix formation with SPG. We have found, as expected, that this cohelical complex emits highly efficient CPL even in an aqueous solution. The appearance of the high CPL property is due to 1) a high quantum yield of the fluorene unit and 2) immobilization of the helically twisted conformation of mPFS in an isolated manner through cohelix formation with SPG. One can propose, therefore, that the SPG/mPFS complex acts as a new high‐performance CPL material with a solvent‐dispersible nanowire structure.     

The Source of “Fairy Rings”: 2‐Azahypoxanthine and its Metabolite Found in a Novel Purine Metabolic Pathway in Plants

Rings or arcs of fungus‐stimulated plant growth occur worldwide; these are commonly referred to as “fairy rings”. In 2010, we discovered 2‐azahypoxanthine (AHX), a compound responsible for the fairy‐ring phenomenon caused by fungus; AHX stimulated the growth of all the plants tested. Herein, we reveal the isolation and structure determination of a common metabolite of AHX in plants, 2‐aza‐8‐oxohypoxanthine (AOH). AHX is chemically synthesized from 5‐aminoimidazole‐4‐carboxamide (AICA), and AHX can be converted into AOH by xanthine oxidase. AICA is one of the members of the purine metabolic pathway in animals, plants, and microorganisms. However, further metabolism of AICA remains elusive. Based on these results and facts, we hypothesized that plants themselves produce AHX and AOH through a pathway similar to the chemical synthesis. Herein, we demonstrate the existence of endogenous AHX and AOH and a novel purine pathway to produce them in plants.     

Shrinking Behavior of Surfactant‐Grafted Thermosensitive Gels and the Mechanism of Rapid Shrinking

Surfactant‐grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm‐co‐S180A) gels prepared using a chemical cross‐linker (bis‐PNS gels) exhibited rapid shrinking, as did PNS gels prepared by γ‐ray irradiation (γ‐PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main‐chain structure. The shrinking kinetics of the bis‐PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis‐PNS gel.