Intramolecular Aminolactonization for Synthesis of Furoindolin-2-One

Propellanes are polycyclic compounds in which tricyclic systems share one carbon–carbon single bond. Propellane frameworks that consist of larger sized rings are found in a variety of natural products. As an approach to the stereoselective synthesis of the propellane framework, one of the efficient methods is forming several rings in a single operation. Lapidilectine B (1) is composed of a propellane framework and was synthesized through the oxidative cyclization of trisubstituted alkenes. When the alkene with an ester moiety was treated with N-iodosuccinimide (NIS), iodocyclization proceeded to give the cyclic carbamate. On the other hand, when PhI(OAc)2 was allowed to react in the carboxyl form, a furoindolin-2-one structure corresponding to the A-B-C ring of lapidilectine B (1) was produced. Furthermore, when Pd(OAc)2 catalyst was used for cyclization under oxidative conditions, the product yield was improved.

Dimethyl 4,5-dichlorophthalate

While endeavoring to synthesize new chlorinated ligands for ruthenium-based metathesis catalysts, the title compound dimethyl 4,5-dichlorophthalate, C10H8Cl2O4, was prepared from commercially available 4,5-dichlorophthalic acid in ∼77% yield. The title molecule, which also finds utility as a precursor molecule for the synthesis of drugs used in the treatment of Alzheimer's disease, shows one carbonyl-containing methyl ester moiety lying nearly co-planar with the chlorine-derivatized aromatic ring while the second methyl ester shows a significant deviation of 101.05 (12)° from the least-squares plane of the aromatic ring. Within the crystal, structural integrity is maintained by the concerted effects of electrostatic interactions involving the electron-deficient carbonyl carbon atom and the electron-rich aromatic ring along the a-axis direction and C—H...O hydrogen bonds between neighboring molecules parallel to b.

Evaluating cepharanthine analogues as natural drugs against SARS-CoV-2

Cepharanthine is a natural of plant origin, and recently demonstrated to have anti-SARS-CoV-2 activity. In order to evaluate the other natural analogues as a potential COVID-19 drug, a total of 24 compounds resembling cepharanthine were extracted from the KNApSAcK database, and their binding affinities to supposed target proteins, namely, spike protein and main protease of SARS-CoV-2, NPC1, and TPC2, were predicted via molecular docking simulations. Selected analogues were further evaluated by a cell-based SARS-CoV-2 infection assay, and the efficacies of cepharanthine (IC50 1.90 uM) and tetrandrine (IC50 10.37 uM) were demonstrated. From a comparison of the docking conformations of these compounds, the diphenyl ester moiety of the molecules was suggested for a putative pharmacophore of the cepharanthine-analogues.

Optical and Thermal Investigations of New Schiff Base/Ester Systems in Pure and Mixed States

New mesomorphic series, 4-hexadecyloxy phenyl-imino-4′-(3-methoxyphenyl)-4″-alkoxybenzoates (An), were prepared and investigated with different thermal and mesomorphic techniques. The synthesized homologous series constitutes four members that differ from each other in the terminal length of flexible chain (n) attached to phenyl ester moiety, which varies between n = 6, 8, 10, and 12 carbons. A lateral CH3O group is attached to the central benzene ring in the meta position with respect to the ester moiety. Molecular structures of all newly prepared homologues were elucidated via FT-IR, 1H and 13C NMR spectroscopy. Mesomorphic and thermal properties were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and the mesophases identified by polarized optical microscopy (POM). DSC and POM examinations revealed that all members of the present series (An) exhibit a purely enantiotropic nematic (N) phase. Comparative evaluations and binary phase diagrams were established between the present homologues and their corresponding shorter one (Bn). The examination revealed that, the length of the flexible alkoxy chain incorporated into the phenylimino moiety is highly effective on the temperature range and stability of the mesophase observed. With respect to the binary mixtures An/Bn, the exhibited N phase showed to cover the whole composition range with eutectic behavior.

The Comparison of Plasma and Cerebrospinal Fluid R(−)- and S(+)-Flurbiprofen Concentration After Intravenous Injection of Flurbiprofen Axetil in Human Subjects

Background: Flurbiprofen axetil is a prodrug that releases the active substance through enzymatic removal of the ester moiety. It is formulated through encapsulation in a lipid microsphere carrier, and widely used to treat perioperative pain. Here, we studied the distribution of R (−)- and S (+)-flurbiprofen in human plasma and cerebrospinal fluid (CSF) after intravenous injection of flurbiprofen axetil.Methods: A total of 70 adult patients undergoing elective lower limb surgery under spinal anesthesia were given a single intravenous injection of 100-mg flurbiprofen axetil. The patients were randomly assigned to 10 groups for plasma and CSF sampling at 10 time points (5–50 min) after subarachnoid puncture and before actual spinal anesthesia. R (−)- and S (+)-flurbiprofen and CSF/plasma ratio were determined by liquid chromatography–tandem mass spectrometry.Results: R (−)-flurbiprofen concentration ranged from 2.01 to 10.9 μg/mL in plasma and 1.46–34.4 ng/mL in CSF. S (+)-flurbiprofen concentration ranged from 1.18 to 10.8 μg/mL in plasma and from 2.53 to 47 ng/mL in CSF. In comparison to S (+)-flurbiprofen, R (−)-flurbiprofen concentration was significantly higher in plasma at all time points (p < 0.05) except at 30 or 40 min, and lower in CSF at all time points (p < 0.05) except at 10, 15 and 40 min. Analysis after correcting drug concentration for body mass index also revealed higher plasma and lower CSF R (−)-flurbiprofen concentration. In comparison to S (+)-flurbiprofen, AUC0–50 for R (−)-flurbiprofen was larger in plasma and smaller in CSF (p < 0.05 for both), and accordingly smaller CSF/plasma AUC0–50 ratio (p < 0.05). There was a positive correlation between R (−)-flurbiprofen concentration and S (+)-flurbiprofen concentration in plasma (r = 0.725, p < 0.001) as well as in CSF (r = 0.718, p < 0.001), and a negative correlation between plasma and CSF concentration of S (+)-flurbiprofen (r = −0.250, p = 0.037), but not R (−)-flurbiprofen.Conclusion: Distribution of R (−)- and S (+)-flurbiprofen in plasma and CSF differed significantly. Penetration of R (−)-flurbiprofen into the CNS was lower than S (+)-flurbiprofen.

Electrically programmable adhesive hydrogels for climbing robots

Although there have been notable advances in adhesive materials, the ability to program attaching and detaching behavior in these materials remains a challenge. Here, we report a borate ester polymer hydrogel that can rapidly switch between adhesive and nonadhesive states in response to a mild electrical stimulus (voltages between 3.0 and 4.5 V). This behavior is achieved by controlling the exposure and shielding of the catechol group through water electrolysis–induced reversible cleavage and reformation of the borate ester moiety. By switching the electric field direction, the hydrogel can repeatedly attach to and detach from various surfaces with a response time as low as 1 s. This programmable attaching/detaching strategy provides an alternative approach for robot climbing. The hydrogel is simply pasted onto the moving parts of climbing robots without complicated engineering and morphological designs. Using our hydrogel as feet and wheels, the tethered walking robots and wheeled robots can climb on both vertical and inverted conductive substrates (i.e., moving upside down) such as stainless steel and copper. Our study establishes an effective route for the design of smart polymer adhesives that are applicable in intelligent devices and an electrochemical strategy to regulate the adhesion.

Synthesis of amides and esters containing furan rings under microwave-assisted conditions

In this work, we present a novel method for the synthesis of ester and amide derivatives containing furan rings (furfural derivatives) under mild synthetic conditions supported by microwave radiation. N-(Furan-2-ylmethyl)furan-2-carboxamide and furan-2-ylmethyl furan-2-carboxylate were produced using 2-furoic acid, furfurylamine, and furfuryl alcohol. The reactions were carried out in a microwave reactor in the presence of effective coupling reagents: DMT/NMM/TsO− or EDC. The reaction time, the solvent, and the amounts of the substrates were optimized. After crystallization or flash chromatography, the final compounds were isolated with good or very good yields. Our method allows for the synthesis of N-blocked amides using N-blocked amino acids (Boc, Cbz, Fmoc) and amine. As well as compounds with a monoamide and ester moiety, products with diamides and diester bonds (N,N-bis(furan-2-ylmethyl)furan-2,5-dicarboxamide, bis(furan-2-ylmethyl) furan-2,5-dicarboxylate, and furan-3,4-diylbis(methylene) bis(furan-2-carboxylate)) were synthesized with moderate yields in the presence of DMT/NMM/TsO– or EDC, using 2,5-furandicarboxylic acid and 3,4-bis(hydroxymethyl)furan as substrates.

Activator-induced quencher-detachment-based turn-on probe with a cationic substrate moiety for acetylcholinestera

We report a choline ester-grafted turn-on fluorescence probe to detect acetylcholinesterase (AChE) in living cells. AChE-mediated hydrolysis of the choline ester moiety producing carboxylate initiates the activation of Cy5 fluorophore...