Azocalix[4]arene Strapped Calix[4]pyrrole: A Confirmable Fluoride Sensor

A new chromogenic fluoride sensor based on 1,3-di-<i>p</i>-nitrophenylazocalix[4]arene-calix[4]pyrrole (<b>1</b>) was designed and synthesized. The color of the solution of probe <b>1</b> changed upon the addition of any F^–, CH₃CO₂^–, PhCO₂^–, and H₂PO₄^– ions. However, from these ions the highly specific sensing of F^– is achieved by the addition of Ca²⁺ which leads to a color change from light sky blue (of <b>1·F</b>^<b>–</b>) back to the original light orange color of <b>1</b>

Tautomeric-Dependent Lactam Cycloaddition with Nitrile Oxide: Facile Synthesis of 1,2,4-Oxadiazole[4,5‑<i>a</i>]indolone Derivatives

A concise, metal-free, and gram-scale strategy to convert indoline-2,3-diones to 1,2,4-oxadiazole­[4,5-<i>a</i>]­indolones through an improved [3 + 2] cycloaddition of α-ketone-lactam with nitrile oxides has been developed. The lactim form of the resonance structure of isatin in protic solvents is the key active dipolarophile that shows chemo- and regioselectivity under experimental and theoretical conditions. This strategy conveniently enabled the assembly of several 1,2,4-oxadiazole­[4,5-<i>a</i>]­indolines with a broad range of functional groups. Compounds <b>3a</b> and <b>4b</b> exhibit cytotoxicity in the NCI/ADR-RES, SKOV3, and OVCAR8 cell lines

Ultrastrong, Transparent Polytruxillamides Derived from Microbial Photodimers

Ultrastrong and transparent bioplastics are generated from fermented microbial monomers. An exotic aromatic amino acid, 4-aminocinnamic acid, was prepared from a biomass using recombinant bacteria, and quantitatively photodimerized, and diacid and diamino monomers that were both characterized by a rigid α-truxillate structure were generated. These two monomers were polycondensed to create the polyamides with a phenylene­cyclobutane repeating backbone such as poly­{(4,4′-diyl-α-truxillic acid dimethyl ester) 4,4′-diacetamido-α-truxillamide} which was processed into amorphous fibers and plastic films having high transparency. In spite of noncrystalline structure, mechanical strength of the fiber is 407 MPa at maximum higher than those of other transparent plastics and borosilicate glasses, presumably due to the tentative molecular spring function of the phenylene­cyclobutanyl backbone