Rational Design of a Uranyl Metal–Organic Framework for the Capture and Colorimetric Detection of Organic Dyes

A new uranyl containing metal–organic framework, RPL-1 : [(UO₂)₂(C₂₈H₁₈O₈)] ^. H₂O (RPL for Radiochemical Processing Laboratory), was prepared, structurally characterized, and the solid-state photoluminescence properties explored. Single crystal X-ray diffraction data reveals the structure of RPL - 1 consists of two crystallographically unique three dimensional, interpenetrating nets with a 4,3-connected tbo topology. Each net contains large pores with an average width of 22.8 Å and is formed from monomeric, hexagonal bipyramidal uranyl nodes that are linked via 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (TCPB) ligands. The thermal and photophysical properties of RPL-1 were investigated using thermogravimetric analysis and absorbance, fluorescence, and lifetime spectroscopies. The material displays excellent thermal stability and temperature dependent uranyl and TCPB luminescence. The framework is stable in aqueous media and due to the large void space (constituting 76 % of the unit cell by volume) can sequester organic dyes, the uptake of which induces a visible change to the color of the material.     

Trifluorosulfonylation Cascade in Allenols: Stereocontrolled Synthesis of Bis(triflyl)enones

Herein, we report investigations embodying the first example of reversal of the native regioselectivity in the reaction of allenols with electrophiles. The effortlessness of C−C bond formation, mild reaction conditions, neither catalysts nor light irradiation, and exquisite selectivity, both in terms of functional-group tolerance and chemo-, site-, and stereo-selectivity, converts this trifluorosulfonylation-rearrangement sequence into an appealing protocol for the preparation of novel functionalized enones. The synthetic utility of this method has been validated by the conversion of the initially prepared bis(triflyl)enones into a variety of bis(triflyl)-functionalized molecules such as 1,3-dienes, allylic alcohols, pyrroles, pyrazoles, and chromenes. Besides, DFT calculations have provided a reliable understanding of observed selectivity.     

Photoredox/Cobalt Dual-Catalyzed Decarboxylative Elimination of Carboxylic Acids: Development and Mechanistic Insight

Recently, dual-catalytic strategies towards the decarboxylative elimination of carboxylic acids have gained attention. Our lab previously reported a photoredox/cobaloxime dual catalytic method that allows the synthesis of enamides and enecarbamates directly from N-acyl amino acids and avoids the use of any stoichiometric reagents. Further development, detailed herein, has improved upon this transformation's utility and further experimentation has provided new insights into the reaction mechanism. These new developments and insights are anticipated to aid in the expansion of photoredox/cobalt dual-catalytic systems.     

Structural Characterization of O‐ and C‐Glycosylating Variants of the Landomycin Glycosyltransferase LanGT2

The structures of the O‐glycosyltransferase LanGT2 and the engineered, C? C bond‐forming variant LanGT2S8Ac show how the replacement of a single loop can change the functionality of the enzyme. Crystal structures of the enzymes in complex with a nonhydrolyzable nucleotide‐sugar analogue revealed that there is a conformational transition to create the binding sites for the aglycon substrate. This induced‐fit transition was explored by molecular docking experiments with various aglycon substrates.     

Asymmetric [3+2] Annulation Approach to 3‐Pyrrolines: Concise Total Syntheses of (−)‐Supinidine, (−)‐Isoretronecanol,and (+)‐Elacomine

An asymmetric [3+2] annulation reaction to form 3‐pyrroline products is reported. Upon treatment with lithium diisopropylamide, readily available ethyl 4‐bromocrotonate is deprotonated and trapped with Ellman imines selectively at the α‐position to yield enantiopure 3‐pyrroline products. This new method is compatible with aryl, alkyl, and vinyl imines. The efficacy of the method is showcased by short asymmetric total syntheses of (−)‐supinidine, (−)‐isoretronecanol, and (+)‐elacomine. This novel annulation approach also works for an aldehyde, thus providing access to a 2,5‐dihydrofuran product in a single step from simple precursors. By modifying the structure of the carbanion nucleophile, an asymmetric vinylogous aza‐Darzens reaction can be realized.     

Exceptional time response,stability and selectivity in doubly-activated phenyl selenium-based glutathione-selective platform

A phenyl-selenium-substituted coumarin probe was synthesized for the purpose of achieving highly selective and extremely rapid detection of glutathione (GSH) over cysteine (Cys)/homocysteine (Hcy) without background fluorescence. The fluorescence intensity of the probe with GSH shows a ∼100-fold fluorescent enhancement compared with the signal generated for other closely related amino acids, including Cys and Hcy. Importantly, the substitution reaction with the sulfhydryl group of GSH at the 4-position of the probe, which is doubly-activated by two carbonyl groups, occurs extremely fast, showing subsecond maximum fluorescence intensity attainment; equilibrium was reached within 100 ms (UV-vis). The probe selectivity for GSH was confirmed in Hep3B cells by confocal microscopy imaging.     

Dicyclohexylammonium bromoacetate: a low molecular mass organogelator with a one‐dimensional secondary ammonium monocarboxylate (SAM) synthon

The asymmetric unit of the title salt, C₁₂H₂₄N⁺·C₂H₂BrO₂⁻, contains a dicyclohexylammonium cation connected to a bromoacetate anion by means of an N—H...O hydrogen bond. In the crystal, the ion pairs assemble via N—H...O interactions, forming zigzag infinite chains parallel to the c axis with the (...H—N—H...O—C—O...)_n motif that is considered to be a prerequisite for ensuring gelation properties of secondary ammonium monocarboxylate salts. The title salt was characterized by FT–IR, X‐ray powder diffraction (XRPD), TG–DTA and ¹H NMR spectroscopy in solution. Gelation experiments revealed that dicyclohexylammonium bromoacetate forms molecular gels with dimethylformamide and dimethyl sulfoxide. Scanning electron microscopy (SEM) was used to reveal morphological features of dried gels.     

Selective glycoprotein detection through covalent templating and allosteric click-imprinting

Many glycoproteins are intimately linked to the onset and progression of numerous heritable or acquired diseases of humans, including cancer. Indeed the recognition of specific glycoproteins remains a significant challenge in analytical method and diagnostic development. Herein, a hierarchical bottom-up route exploiting reversible covalent interactions with boronic acids and so-called click chemistry for the fabrication of glycoprotein selective surfaces that surmount current antibody constraints is described. The self-assembled and imprinted surfaces, containing specific glycoprotein molecular recognition nanocavities, confer high binding affinities, nanomolar sensitivity, exceptional glycoprotein specificity and selectivity with as high as 30 fold selectivity for prostate specific antigen (PSA) over other glycoproteins. This synthetic, robust and highly selective recognition platform can be used in complex biological media and be recycled multiple times with no performance decrement.