Synthesis of adamantane derivatives—XXX: Synthesis of some adamantane spiro heterocycles by utilizing ionic- and cycloadditions

Synthesis and some reactions of adamantane spiro heterocycles such as aziridine, oxaziridine, azetidine and 1,2-diazetidine derivatives have been described.The 1,3-dipolar cycloadditions of methyleneadmantane (2) and adamantylidenecyanoacrylate (14) have also been reported as a facile route to some 5-membered adamantane spiro heterocycles.     

Anomalous magnetotransport phenomena in θ-(BEDT-TTF)2I3

Anomalous magnetotransport phenomena have been observed in θ-(BEDT-TTF)₂I₃ crystals at temperatures below 15 K. The magnetoresistance M : (1) is a linear function of the magnetic field H, (2) is not affected by the angle between the electric current and the magnetic field, (3) but depends on the magnetic field orientation with respect to the crystal axis. Magnetoresistance is expressed as M = (aH²_a + bH²_b + cH²_c)₀^-3/2/H in terms of H = (H_a, H_b, H_c), the zero field resistivity ₀, and parameters a, b, and c which are independent of temperature and magnetic field. We have found that b a > c. Magnetoresistance up to 40 is observed for H = 7T along the b-axis at T = 1.5K.     

A structure-biological activity study based on cluster analysis and the nonlinear mapping method of pattern recognition

Cluster analysis is used in a study of structure—activity relationships of biologically active compounds. A hierarchal clustering technique was applied to 29 typical antibiotics using 27 antibacterial activities. These antibiotics were of various types; penicillins, cephalosporins, aminoglycosides, macrolides, tetracyclines, and peptides. The result was obtained as a branching tree diagram. The technique allowed the antibiotics to be distributed into 6 clusters, each cluster mostly consisting of compounds with a similar structure. Nonlinear mapping was used to display the 27-dimensional data structure of the antibiotics. The nonlinear map was compared with the clusters obtained by cluster analysis.     

A novel synthesis of benzofuran and related compounds. III. The vilsmeier reaction of phenoxyacetaldehyde diethyl acetals

A novel synthesis of 2-benzofurancarbaldehydes by the Vilsmeier reaction of phenoxyacetaldehyde diethyl acetals is described.     

Regulating Higher‐Order Organization through the Synergy of Two Self‐Sorted Assemblies

The extracellular matrix (ECM) is the natural fibrous scaffold that regulates cell behavior in a hierarchical manner. By mimicking the dynamic and reciprocal interactions between ECM and cells, higher‐order molecular self‐assembly (SA), mediated through the dynamic growth of scaffold‐like nanostructures assembled by different molecular components, was developed. Designed and synthesized were two self‐sorted coumarin‐based gelators, a peptide molecule and a benzoate molecule, which self‐assemble into nanofibers and nanobelts, respectively, with different dynamic profiles. Upon the dynamic growth of the fibrous scaffold assembled from peptide gelators, nanobelts assembled from benzoate gelators transform into a layer‐by‐layer nanosheet, reaching ninefold increase in height. By using light and an enzyme, the spatial–temporal growth of the scaffold can be modified, leading to in situ height regulation of the higher‐order architecture.     

NMR characterization of α- and β-mannopyranurono-2,6-lactones

Determining the stereochemistry at the anomeric position of glycosides is imperative in chemical synthesis. As for 1,2-cis-β-glycosides such as β-mannosides, ¹³C-¹H coupling constants, ¹J_CHs, are conventionally used when glycosides are in an ordinary chair conformation. In this work, we searched for appropriate criteria to determine the stereochemistry of products in a recently developed glycosylation reaction using 2,6-lactones. As a result, we found that α-glycosides exhibited vicinal coupling constants of around 3.0?Hz?at the anomeric proton, as well as a long-range coupling between protons at C-1 and C-5, whereas β-glycosides had coupling constants of 1.2?Hz?at most. These figures are expected to be useful for future assignments. In addition, the observations obtained from this study revealed the conformation of glycosides with a 2,6-lactone moiety.