Epimerization of Lupinine to Epilupinine and vice versa. Reexamination of the Structures of Lupinal and Epilupinal

Although the epimerization of lupinine ( 1 ) has been largely investigated, a previously not observed compound of formula C₁₀H₁₇NO was now isolated from the mixture of alkaloids that remains after the separation of epilupinine ( 2 ). It is insoluble in dry Et₂O but soluble in EtOH, from which it is recovered as an Et₂O‐soluble oil that slowly returns to the Et₂O‐insoluble solid form. For these characteristics and based on GC/MS, ¹H‐NMR, and IR data, it is considered as the inner salt 6 of the common enolic form 5 of lupinal ( 3 ) and epilupinal ( 4 ), with which it is in equilibrium when standing in solution (see Scheme 1). The oily form, but not the solid one, is able to improve the conversion of 1 to 2 , establishing the role of the aldehydes in the epimerization process. It was observed that also 2 can be converted to 1 . Finally, the solid lupinal described by Zaboev should be considered as being identical to the now isolated inner salt 6 , while the oily epilupinal of Wicky and Schumann is, indeed, a mixture of epilupinal ( 4 ) with a minor amount of lupinal ( 3 ), which, on standing, is converted to the inner salt 6 of the common enolic form 5 .     

On a class of finite linear spaces with few lines

A famous result of de Bruijn and Erdős (Indag. Math. 10 (1948) 421–423) states that a finite linear space has at least as many lines as points, with equality only if it is a projective plane or a near-pencil. This result led to the problem of characterizing finite linear spaces for which the difference between the number b of lines and the number v of points is assigned.

In this paper finite linear spaces with b−vm, m being the minimum number of lines on a point, are characterized.     

Chelating Phosphorus–An O,C, O-Coordinating Pincer-Type Ligand Coordinating PIII and PV Centres

The sequence of reactions of the phosphorus-containing aryllithium compound 5-t-Bu-1,3-[(P(O)(O-i-Pr)₂]₂C₆H₂Li (ArLi) with Ph₂PCl, KMnO₄, elemental sulfur and elemental selenium, respectively, gave the aryldiphenylphosphane chalcogenides 5-t-Bu-1,3-[(P(O)(O-i-Pr)₂]₂C₆H₂P(E)Ph₂ ( 1 , E=O; 2 , E=S; 3 , E=Se). Compound 1 partially hydrolysed giving [5-t-Bu-1-{(P(O)(O-i-Pr)₂}-3-{(P(O)(OH)₂}C₆H₂]P(O)Ph₂ ( 4 ). The reaction of ArLi with PhPCl₂ provided the benzoxaphosphaphosphole [1(P), 3(P)-P(O)(O-i-Pr)OPPh-6-t-Bu-4-P(O)(O-i-Pr)₂]C₆H₂P ( 5i ) as a mixture of the two diastereomers. The oxidation of 5i with elemental sulfur gave the benzoxaphosphaphosphole sulfide [1(P), 3(P)-P(O)(O-i-Pr)OP(S)Ph-6-t-Bu-4-P(O)(O-i-Pr)₂]C₆H₂ ( 5 ) as pair of enantiomers P1(R), P3(S)/P1(S), P3(R) of the diastereomer (RS/SR)- 5 ( 5b ). The aryldiphenylphosphane 5-t-Bu-1,3-[(P(O)(O-i-Pr)₂]₂C₆H₂PPh₂ ( 6 ) was obtained from the reaction of the corresponding aryldiphenylphosphane sulfide 2 with either sodium hydride, NaH, or disodium iron tetracarbonyl, Na₂Fe(CO)₄. The oxidation of the aryldiphenylphosphane 6 with elemental iodine and subsequent hydrolysis yielded the aryldiphenyldioxaphosphorane 9-t-Bu-2,6-(OH)-4,4-Ph₂-3,5-O₂-2,6-P₂-4λ⁵-P-[5.3.1.0]-undeca-1(10),7(11),8-triene ( 7 ). Both of its diastereomers, (RR/SS)- 7 ( 7a ) and (RS/SR)- 7 ( 7b ), were separated as their chloroform and i-propanol solvates, 7a ⋅2CHCl₃ and 7b ⋅i-PrOH, respectively. DFT calculations accompanied the experimental work.     

Cross‐linking of poly(methyl methacrylate) by oxozirconate and oxotitanate clusters

Radical polymerization of methyl methacrylate with 0.5‐2 mol% of the (meth)acrylate‐substituted oxozirconium and oxotitanium clusters Zr₆(OH)₄O₄(OMc)₁₂ (OMc = methacrylate), Zr₄O₂(OMc)₁₂, Ti₆O₄(OEt)₈(OMc)₈ and Ti₄O₂(OPrⁱ)₆(OAcr)₆ (OAcr = acrylate) results in an efficient cross‐linking of the organic polymers. The obtained inorganic‐organic hybrid polymers exhibit a higher thermal stability due to inhibited depolymerization reactions. Contrary to undoped poly(methyl methacrylate), the cluster cross‐linked polymers are insoluble but swell in organic solvents. The solvent uptake upon swelling decreases with an increasing amount of polymerized cluster. The impedance spectra of PMMA doped with various proportions of Zr₄O₂(OMc)₁₂ show that the capacitance of the polymers decreases with an increasing proportion of the cluster. The polymer doped with 2 mol% of Zr₄O₂(OMc)₁₂ shows an increase in conductivity to 0.9·10⁻⁷ S·cm⁻¹ at 74°C.     

Panchromatic Fluorescence Emission from Thienosquaraines Dyes: White Light Electrofluorochromic Devices

Electrofluorochromic devices (EFCDs) that allow the modulation of the light emitted by electroactive fluorophores are very attractive in the research field of optoelectronics. Here, the electrofluorochromic behaviour of a series of squaraine dyes was studied for the first time. In solutions, all compounds are photoluminescent with maxima located in the range 665–690 nm, characterized by quantum yields ranging from 30% to 4.1%. Squaraines were incorporated in a polymer gel used as an active layer in all-in-one gel switchable EFCDs. An aggregation induced quenching occurs in the gel phase, causing a significant decrease in the emission quantum yield in the device. However, the squaraines containing the thieno groups (thienosquaraines, TSQs) show a panchromatic emission and their electrofluorochromism allows the tuning of the fluorescence intensity from 500 nm to the near infrared. Indeed, the application of a potential difference to the device induces a reversible quenching of their emission that is significantly higher and occurs at shorter switching times for TSQs-based devices compared to the reference squaraine dye (DIBSQ). Interestingly, the TSQs fluorescence spectral profile becomes more structured under voltage, and this could be explained by the shift of the aggregates/monomer equilibrium toward the monomeric species, due to electrochemical oxidation, which causes the disassembling of aggregates. This effect may be used to modulate the colour of the fluorescence light emitted by a device and paves the way for conceiving new electrofluorochromic materials based on this mechanism.     

Zeolitic inorganic–organic polymer electrolytes: a material based on poly(ethylene glycol) 600, SnCl4 and K4Fe(CN)6

This report describes the synthesis of a new zeolitic inorganic–organic polymer electrolyte with the formula [Fe_xSn_y(CN)_zCl_v(C_2nH_4n+2O_n+1)K₁]. This material is based on poly(ethylene glycol) 600, SnCl₄ and K₄[Fe(CN)₆], and is obtained via a sol→gel transition. Mid and far Fourie than form infrared (FT‐IR) studies, analytical data and X‐ray Photoelectron spectroscopy (XPS) investigations allowed us to conclude that this material is a mixed inorganic–organic network in which Fe and Sn are bonded by CN bridges and tin atoms by PEG 600 bridges. Mid‐infrared (MIR) FT‐IR investigations demonstrated that the polyether chains assume a conformation of the TGT (T = trans, G = gauche) type. Micrographs of the compound obtained by scanning electron microscopy reveal that its morphology resembles a smooth gummy paste. The conductivity of the material at different temperatures was determined by impedance spectroscopy (IS). Results indicated that the material conducts ionically and that its conductivity is strongly influenced by segmental motion of the polymer network. Finally, this network shows a conductivity of ca. 3.7 × 10⁻⁵ S/cm at 25 °C. Copyright © 2000 John Wiley & Sons, Ltd.     

A New Butyrate Releaser Exerts a Protective Action against SARS-CoV-2 Infection in Human Intestine

Butyrate is a major gut microbiome metabolite that regulates several defense mechanisms against infectious diseases. Alterations in the gut microbiome, leading to reduced butyrate production, have been reported in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. A new butyrate releaser, useful for all the known applications of butyrate, presenting physiochemical characteristics suitable for easy oral administration, (N-(1-carbamoyl-2-phenyl-ethyl) butyramide (FBA), has been recently developed. We investigated the protective action of FBA against SARS-CoV-2 infection in the human small intestine and enterocytes. Relevant aspects of SARS-CoV-2 infection were assessed: infectivity, host functional receptor angiotensin-converting enzyme-2 (ACE2), transmembrane protease serine 2 (TMPRSS2), neuropilin-1 (NRP1), pro-inflammatory cytokines expression, genes involved in the antiviral response and the activation of Nf-kB nuclear factor (erythroid-derived 2-like) 2 (Nfr2) pathways. We found that FBA positively modulates the crucial aspects of the infection in small intestinal biopsies and human enterocytes, reducing the expression of ACE2, TMPRSS2 and NRP1, pro-inflammatory cytokines interleukin (IL)-15, monocyte chemoattractant protein-1 (MCP-1) and TNF-α, and regulating several genes involved in antiviral pathways. FBA was also able to reduce the number of SARS-CoV-2-infected cells, and ACE2, TMPRSS2 and NRP1 expression. Lastly, through the inhibition of Nf-kB and the up-regulation of Nfr2, it was also able to reduce the expression of pro-inflammatory cytokines IL-15, MCP-1 and TNF-α in human enterocytes. The new butyrate releaser, FBA, exerts a preventive action against SARS-CoV-2 infection. It could be considered as an innovative strategy to limit COVID-19.