Tertiary-butoxycarbonyl (Boc) – A strategic group for N-protection/deprotection in the synthesis of various natural/unnatural N-unprotected aminoacid cyanomethyl esters

A number of cyanomethyl esters of natural/unnatural aminoacids with un-protected amino functionality were synthesized because of their synthetic and medicinal importance. Critical N-Boc deprotection methods in the presence of labile (hydrolytic sensitivity) cyanomethyl functionality were screened thoroughly and it was found that readily available 4M HCl in 1,4-dioxane solution (2–4 equiv); acetonitrile, 0?°C, 2–4?h was a suitable condition. This condition was generalized and successfully applied to a variety of alkyl, alkynyl, aryl, heteroaryl, benzyl, azido, spiro amino acid cyanomethylesters irrespective of the nature of the amine (primary or secondary) and the distance between the amine and ester group to achieve final deprotected amino esters with high yield, and purity compared to other commonly known N-protecting groups (Cbz, Fmoc, Ac, Bn, Bz etc.). It was also demonstrated that N-Boc protected aminoacid cyanomethylesters are stable enough to carry out further functionalization compared to N-unprotected counterparts.     

Galvanostatic Entrapment of Sulfite Oxidase into Ultrathin Polypyrrole Films for Improved Amperometric Biosensing of Sulfite

The entrapment of sulfite oxidase (SOx) into ultrathin polypyrrole (PPy) films of 27–135 nm thickness has been successfully used for amperometric biosensing of sulfite with considerably improved performance. Optimum galvanostatic entrapment was accomplished in an electrolyte‐free solution which contained 0.1 M pyrrole and 5 U/mL of SOx with a polymerization period of 120 seconds and an applied current density of 0.2 mA cm^?2. Evidence of the incorporation and retention of SOx in the ultrathin PPy film was obtained by scanning electron microscopy, cyclic voltammetry and amperometric measurements. Entrapment of the enzyme in a 54 nm thick PPy‐SOx film gave optimum amperometric response for sulfite and enabled the detection of as little as 0.9 μM of sulfite with a linear concentration range of 0.9 to 400 μM. The successful application of the biosensor to the determination of sulfite in beer and wine samples is reported. Comparison with a spectrophotometric method indicates that the biosensor was more superior for the determination of sulfite in red wine.     

Metal-Free Arylation of Benzothiophenes at C4 by Activation as their Benzothiophene S-Oxides

Benzothiophenes, activated by oxidation to the corresponding S-oxides, undergo C−H/C−H-type coupling with phenols to give C4 arylation products. While an electron-withdrawing group at C3 of the benzothiophene is important, the process operates without a directing group and a metal catalyst, thus rendering it compatible with sensitive functionalities—e.g. halides and formyl groups. Quantum chemical calculations suggest a formal stepwise mechanism involving heterolytic cleavage of an aryloxysulfur species to give a π-complex of the corresponding benzothiophene and a phenoxonium cation. Subsequent addition of the phenoxonium cation to the C4 position of the benzothiophene is favored over the addition to C3; Fukui functions predict that the major regioisomer is formed at the more electron-rich position between C3 and C4. Varied selective manipulation of the benzothiophene products showcase the synthetic utility of the metal-free arylation process.     

3D Printable Geopolymer Composites Reinforced with Carbon-Based Nanomaterials – A Review

Three-dimensional (3D) geopolymer printing (3DGP) technology is a rapidly evolving digital fabrication method used in the construction industry. This technology offers significant benefits over 3D concrete printing in terms of energy saving and reduced carbon emissions, thus promoting sustainability. 3DGP technology is still evolving, and researchers are striving to develop high-performance printable materials and different methods to improve its robustness and efficiency. Carbon-based nanomaterials (CBNs) with beneficial properties have a wide range of applications in various fields, including as concrete/geopolymer systems in construction. This paper comprehensively reviews the research progress on carbon-based nanomaterials (CBNs) used to develop extrusion-based 3D geopolymer printing (3DGP) technology, including dispersion techniques, mixing methods, and the materials′ performance. The rheological, mechanical, durability, and other characteristics of these materials are also examined. Furthermore, the existing research limitations and the prospects of using 3DGP technology to produce high-quality composite mixtures are critically evaluated.     

Prednisone/Cyclodextrin Inclusion Complexation: Phase Solubility,Thermodynamic, Physicochemical and Computational Analysis

Guest–host interaction of prednisone (PN) with cyclodextrins (CDs) have been investigated using phase solubility diagrams (PSD), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), scanning electron microscopy (SEM) and molecular mechanical modeling (MM). Estimates of the complex formation constant (K ₁₁) show that the tendency of PN to complex with CDs follows the order: β-CD>γ-CD>HP-β-CD>α-CD. At the same pH of 7.0, β-CD forms soluble 1:1 and insoluble 1:2 PN/CD complexes (B_S-type PSDs). The thermodynamic functions for 1:1 PN/β-CD estimated at pH = 7.0 (ΔG ₁₁^o=−20.8 kJ⋅mol⁻¹) show that complexation is driven by enthalpy (−30.7 kJ⋅mol⁻¹) but retarded by entropy (ΔS ₁₁^o=−33.1 J⋅mol⁻¹⋅K⁻¹) changes. The MM modeling study indicates the formation of different isomeric 1:1 complexes with CDs. PSD, DSC, XRPD, SEM and MM studies established the formation of inclusion complexes in solution and the solid state.     

Recent Insights Into the Biomedical Applications of Shape‐memory Polymers

Shape‐memory polymers (SMP) are versatile stimuli‐responsive materials that can switch, upon stimulation, from a temporary to a permanent shape. This advanced functionality makes SMP suitable and promising materials for diverse technological applications, including the fabrication of smart biomedical devices. In this paper, advances in the design of SMP are discussed, with emphasis on materials investigated for medical applications. Future directions necessary to bring SMP closer to their clinical application are also highlighted.

     

Prediction of flow and heat transfer in narrow rotating rectangular channels using Reynolds stress model

A computational study is performed on three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with aspect ratio (AR) of 10:1, oriented 120° from the direction of rotation. The Focus is on high rotation and high-density ratios effects on the heat transfer characteristics of the 120° orientation. The Reynolds stress model (RSM), which accounts for rotational effects are used to compute the turbulent flow and heat transfer in the rotating channel. The effects of rotation and coolant-to-wall density ratio on the fluid flow and heat transfer characteristics is reported on a range of rotation numbers and density ratios (0 < Ro < 0.25 and 0.07 < Δρ/ρ < 0.4). The computational results are in good agreement with experimental data within ±15%. The results show that the density ratio, rotation number and channel orientation significantly affect the flow field and heat transfer characteristics in the rotating rectangular channel. Flow reversal occurs at high rotation number and density ratio.     

The Internal Bremsstrahlung Accompanying the Electron Capture Decay of 57Co

The internal bremsstrahlung (IB) spectrum accompanying the electron capture decay of ⁵⁷Co have been measured. The measured spectrum was then analyzed into its constituting gamma lines. The proper corrections for the analyzed IB (EC) spectrum have been taken into account. A comparison between the present experimental results of the IB (EC) probability per electron capture and those calculated theoretically according to Martin and Glauber theory have been done. This comparison shows a good agreement throught the investigated range of energy (300 up to 650 keV).     

On completely hyperexpansive operators

We introduce and discuss a class of operators, to be referred to as the class of completely hyperexpansive operators, which is in some sense antithetical to the class of contractive subnormals. The new class is intimately related to the theory of negative definite functions on abelian semigroups. The known interplay between positive and negative definite functions from the theory of harmonic analysis on semigroups can be exploited to reveal some interesting connections between subnormals and completely hyperexpansive operators.

     

Internal Bremsstrahlung accompanying non-unique second-forbiddenβ-decay of36CL

The inner Bremsstrahlung spectrum (I.B.) associated wih the non-unique second forbidden-transition of³⁶Cl was measured using a single channel NaI (Tl) scintillation spectrometer. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to the KUB, Lewis and Ford, Nilsson, Ford and Martin and Chang and Falkoff. Also a comparison with those calculated according to Nilsson theory after applying the shape correction factor (M. KUB) was done. The measured spectrum is found to show fairly good agreement with M. KUB theory and its found to deviate therafter from all five theories.The authors would like to thank Prof. Dr. M. El-Nadi and Prof. Dr. O.E. Badawy for their suggestions, interest and encouragement.