Bleomycin modulates amyloid aggregation in β-amyloid and hIAPP

Aberrant misfolding and amyloid aggregation, which result in amyloid fibrils, are frequent and critical pathological incidents in various neurodegenerative disorders. Multiple drugs or inhibitors have been investigated to avert amyloid aggregation in individual peptides, exhibiting sequence-dependent inhibition mechanisms. Establishing or inventing inhibitors capable of preventing amyloid aggregation in a wide variety of amyloid peptides is quite a daunting task. Bleomycin (BLM), a complex glycopeptide, has been widely used as an antibiotic and antitumor drug due to its ability to inhibit DNA metabolism, and as an antineoplastic, especially for solid tumors. In this study, we investigated the dual inhibitory effects of BLM on Aβ aggregation, associated with Alzheimer''s disease and hIAPP, which is linked to type 2 diabetes, using both computational and experimental techniques. Combined results from drug repurposing and replica exchange molecular dynamics simulations demonstrate that BLM binds to the β-sheet region considered a hotspot for amyloid fibrils of Aβ and hIAPP. BLM was also found to be involved in β-sheet destabilization and, ultimately, in its reduction. Further, experimental validation through in vitro amyloid aggregation assays was obtained wherein the fibrillar load was decreased for the BLM-treated Aβ and hIAPP peptides in comparison to controls. For the first time, this study shows that BLM is a dual inhibitor of Aβ and hIAPP amyloid aggregation. In the future, the conformational optimization and processing of BLM may help develop various efficient sequence-dependent inhibitors against amyloid aggregation in various amyloid peptides.

Bleomycin acts as a dual inhibitor against both amyloid β and human islet amyloid polypeptide by binding to the β-sheet grooves considered as the amyloids hotspot.     

Oxygen Equilibrium Characteristics of Abnormal Hemoglobins: Hirose (α2β237Ser), L Ferrara (α247Glyβ2), Broussais (α290Asnβ2), and Dhofar (α2β258Arg)

The oxygen equilibrium characteristics of four structural variants of hemoglobin A were correlated with their amino acid substitutions.Hemoglobin Dhofar, in which the proline at E2(58)beta is replaced by arginine, had normal oxygen equilibrium characteristics.Hemoglobin L Ferrara. in which the aspartic acid at CD5(47)alpha is replaced by glycine, and hemoglobin Broussais, in which the lysine at FG2(90)alpha is replaced by asparagine, both showed a slightly elevated oxygen affinity; nevertheless both demonstrated a normal heme-heme interaction and a normal Bohr effect.Hemoglobin Hirose, in which the tryptophan at C3 (37)beta is replaced by serine, showed abnormalities of all oxygen equilibrium characteristics; i.e., increased oxygen affinity, diminished heme-heme interaction, and reduced Bohr effect.These results suggest that aspartic acid at CD5(47)alpha and lysine at FG2(90)alpha are involved in the function of the hemoglobin molecule, despite the fact that these positions are not located directly in the heme or the alpha-beta-contact regions.Tryptophan at C3(37)beta is located at contact between alpha(1)- and beta(2)-subunits. It is suggested that the substitution by serine might disturb the quarternary structure of the mutant hemoglobin molecule during transition from oxy-form to deoxy-form resulting in an alteration of the heme function.     

Catalyst-free chemoselective α-sulfenylation/β-thiolation for α,β-unsaturated carbonyl compounds

A novel, efficient, catalyst-free and product-controllable strategy has been developed for the chemoselective α-sulfenylation/β-thiolation of α,β-unsaturated carbonyl compounds. An aromatic sulfur group could be chemoselectively introduced at α- or β-position of carbonyls with different sulfur reagents under slightly changed reaction conditions. A series of desired products were obtained in moderate to excellent yields. Mechanistic studies revealed that B₂pin₂ played the key role in activating the transformation towards the β-thiolation of α,β-unsaturated carbonyl compounds. This transition-metal-catalyst-free method provides a convenient and efficient tool for the highly chemoselective preparation of α-thiolation or β-sulfenylation products of α,β-unsaturated carbonyl compounds.

This catalyst-free method provides a useful and efficient tool for the highly chemoselective preparation of α-thiolation or β-sulfenylation products of α,β-unsaturated carbonyl compounds.     

Electrophilic halogenations of propargyl alcohols: paths to α-haloenones, β-haloenones and mixed β,β-dihaloenones

The Meyer–Schuster rearrangement of propargyl alcohols or alkynols leading to α,β-unsaturated carbonyl compounds is well known. Yet, electrophilic halogenations of the same alkynols and their alkoxy, ester and halo derivatives are inconspicuous. This review on the halogenation reactions of propargyl alcohols and derivatives intends to give a perspective from its humble direct halogenation beginning to the present involving metal catalysis. The halogenation products of propargyl alcohols include α-fluoroenones, α-chloroenones, α-bromoenones and α-iodoenones, as well as β-haloenones and symmetrical and mixed β,β-dihaloenones. They are, in essence, tri and tetrasubstituted alkenes carrying halo-functionalization at the α- or β-carbon. This is a potential stepping stone for further construction towards challenging substituted alkenones via Pd-catalysed coupling reactions.

This review highlights the development of α-haloenone, β-haloenone and mixed β,β-dihaloenone formations from propargyl alcohols via direct electrophilic halogenations and metal catalysed-halonium interception rearrangements.     

Thermal stability and oxidation characteristics of α-pinene, β-pinene and α-pinene/β-pinene mixture

Turpentine is a renewable resource, has good combustion performance, and is considered to be a fuel or promising additive to diesel fuel. This is very important for the investigation of thermal stability and energy oxidation characteristics, because evaluation of energy or fuel quality assurance and use safety are necessary. The main components of turpentine are α-pinene and β-pinene, which have unsaturated double bonds and high chemical activity. By investigating their thermal stability and oxidation reaction characteristics, we know the chemical thermal properties and thermal explosion hazard of turpentine. In this present study, the thermal stability and oxidation characteristics of α-pinene, β-pinene and α-pinene/β-pinene mixture were investigated using a high sensitivity accelerating rate calorimeter (ARC) and C80 calorimeter. The important parameters of oxidation reaction and thermal stability were obtained from the temperature, pressure and exothermic behavior in chemical reaction. The results show that α-pinene and β-pinene are thermally stable without chemical reaction under a nitrogen atmosphere even when the temperature reaches 473 K. The initial exothermic temperature of the two pinenes and their mixture is 333–338 K, and the heat release (−ΔH) of their oxidation is 2745–2973 J g⁻¹. The oxidation activation energy (E_a) of α-pinene, β-pinene and α-pinene/β-pinene mixture is 116.25 kJ mol⁻¹, 121.85 kJ mol⁻¹, and 115.95 kJ mol⁻¹, respectively. There are three steps in the oxidation of pinenes: the first is the induction period of the oxidation reaction; the second is the main oxidation stage, and the pressure is reduced; the third is thermal decomposition to produce gas.

Turpentine is a renewable resource, has good combustion performance, and is considered to be a fuel or promising additive to diesel fuel.     

Inhibition of β-Lactamases by β-Lactam Antibiotics

The inhibitory properties of a selected number of beta-lactam antibiotics were studied, with the use of three distinct types of beta-lactamases. The three enzymes were found to be distinguishable on the basis of their susceptibility to inhibition. Not one of the potential inhibitors tested was found to be a potent inhibitor of all three enzymes, but nafcillin possessed the broadest inhibitory activity. The enzyme isolated from Enterobacter cloacae was found to be the most susceptible. In some cases, the degree of inhibition varied with the time of incubation, and, depending upon the time chosen, widely different observations could be made. It is suggested that, in studies such as these, every consideration should be given to the period of incubation and to the concentration of inhibitor employed. Mixtures of inhibitor and cephaloridine did not always act synergistically against growing bacteria, and a number of reasons for failure are suggested.     

Direct β-selectivity of α,β-unsaturated γ-butyrolactam for asymmetric conjugate additions in an organocatalytic manner

The β-selective asymmetric addition of γ-butyrolactam with cyclic imino esters catalyzed by a bifunctional chiral tertiary amine has been developed, which provides an efficient access to optically active β-position functionalized pyrrolidin-2-one derivatives in both high yield and enantioselectivity (up to 78% yield and 95 : 5 er). This is the first catalytic method to access chiral β-functionalized pyrrolidin-2-one via a direct organocatalytic approach.

The asymmetric addition of γ-butyrolactam with cyclic imino esters catalyzed by (DHQD)₂AQN has been developed, which provides an access to β-position functionalized pyrrolidin-2-one derivatives in high levels yield and enantioselectivity.

Metal-free organocatalytic asymmetric transformations have successfully captured considerable enthusiasm of chemists as powerful methods for the synthesis of various kinds of useful chiral compounds ranging from the preparation of biologically important molecules through to novel materials.¹ Chiral pyrrolidin-2-ones have been recognized as important structural motifs that are frequently encountered in a variety of biologically active natural and synthetic compounds.² In particular, the β-position functionalized pyrrolidin-2-one backbones, which can serve as key synthetic precursors for inhibitory neurotransmitters γ-aminobutyric acids (GABA),³ selective GABA_B receptor agonists⁴ as well as antidepressant rolipram analogues,⁵ have attracted a great deal of attention. Therefore, the development of highly efficient, environmentally friendly and convenient asymmetric synthetic methods to access these versatile frameworks is particularly appealing.As a direct precursor to pyrrolidin-2-one derivatives, recently, α,β-unsaturated γ-butyrolactam has emerged as the most attractive reactant in asymmetric organometallic or organocatalytic reactions for the synthesis of chiral γ-position functionalized pyrrolidin-2-ones (Scheme 1). These elegant developments have been achieved in the research area of catalytic asymmetric vinylogous aldol,⁶ Mannich,⁷ Michael⁸ and annulation reactions⁹ in the presence of either metal catalysts or organocatalysts (a, Scheme 1). These well-developed catalytic asymmetric methods have been related to the γ-functionalized α,β-unsaturated γ-butyrolactam to date. However, in sharp contrast, the approaches toward introducing C-3 chirality at the β-position of butyrolactam through a direct catalytic manner are underdeveloped (b, Scheme 1)¹⁰ in spite of the fact that β-selective chiral functionalization of butyrolactam can directly build up α,β-functionalized pyrrolidin-2-one frameworks.Open in a separate windowScheme 1Different reactive position of α,β-unsaturated γ-butyrolactam in catalytic asymmetric reactions.So far, only a few metal-catalytic enantioselective β-selective functionalized reactions have been reported. For examples, a rhodium/diene complex catalyzed efficient asymmetric β-selective arylation^10a and alkenylation^10b have been reported by Lin group (a, Scheme 2). Procter and co-workers reported an efficient Cu(i)–NHC-catalyzed asymmetric silylation of unsaturated lactams (b, Scheme 2).^10c Despite these creative works, considerable challenges still exist in the catalytic asymmetric β-selective functionalization of γ-butyrolactam. First, the scope of nucleophiles is limited to arylboronic acids, potassium alkenyltrifluoroborates and PhMe₂SiBpin reagents. Second, the catalytic system and activation mode is restricted to metal/chiral ligands. To our knowledge, an efficient catalytic method to access chiral β-functionalized pyrrolidin-2-one via a direct organocatalytic approach has not yet been established. Therefore, the development of organocatalytic asymmetric β-selective functionalization of γ-butyrolactam are highly desirable. In conjunction with our continuing efforts in building upon chiral precedents by using chiral tertiary amine catalytic system,¹¹ we rationalized that the activated α,β-unsaturated γ-butyrolactam might serve as a β-position electron-deficient electrophile. This γ-butyrolactam may react with a properly designed electron-rich nucleophile to conduct an expected β-selective functionalized reaction of γ-butyrolactam under a bifunctional organocatalytic fashion, while avoiding the direct γ-selective vinylogous addition reaction or β,γ-selective annulation as outlined in Scheme 2. Herein we report the β-selective asymmetric addition of γ-butyrolactam with cyclic imino esters¹² catalyzed by a bifunctional chiral tertiary amine, which provides an efficient and facile access to optically active β-position functionalized pyrrolidin-2-one derivatives with both high diastereoselectivity and enantioselectivity.Open in a separate windowScheme 2β-Selective functionalization of γ-butyrolactam via metal- (previous work) or organo- (this work) catalytic approach.To begin our initial investigation, several bifunctional organocatalysts¹³ were firstly screened to evaluate their ability to promote the β-selective asymmetric addition of γ-butyrolactam 2a with cyclic imino ester 3a in the presence of 15 mol% of catalyst loading at room temperature in CH₂Cl₂ (entries 1–6,

Equal synthesis of α- and β-globin chains in erythroid precursors in heterozygous β-thalassemia

In patients with heterozygous beta-thalassemia, the beta/alpha synthetic ratio in marrow erythroid cells incubated in vitro is 1, whereas in reticulocytes the ratio is 0.5. These ratios reflect the equal synthesis of the two chains on the polyribosomes of the bone marrow and unequal synthesis on the polyribosomes of the peripheral blood reticulocytes. alpha- and beta-chain synthesis is also equal in marrow cells in vivo. Equal synthesis is probably due both to a decrease in alpha-chain synthesis and an increase in beta-chain synthesis in bone marrow erythroid cells and may contribute to the absence of overt hemolysis due to excess alpha-globin chain accumulation in heterozygous beta-thalassemia.     

Hydrophilic and organophilic pervaporation of industrially important α,β and α,ω-diols

The distillation-based purification of α,β and α,ω-diols is energy and resource intensive, as well as time consuming. Pervaporation separation is considered to be a remarkable energy efficient membrane technology for purification of diols. Thus, as a core pervaporation process, hydrophilic polyvinyl alcohol (PVA) membranes for the removal of water from 1,2-hexanediol (1,2-HDO) and organophilic polydimethylsiloxane–polysulfone (PDMS–PSF) membranes for the removal of isopropanol from 1,5 pentanediol (1,5-PDO) were employed. For 1,2-HDO/water separation using a feed having a 1 : 4 weight ratio of 1,2-HDO/water, the membrane prepared using 4 vol% glutaraldehyde (GA4) showed the best performance, yielding a flux of 0.59 kg m⁻² h⁻¹ and a separation factor of 175 at 40 °C. In the organophilic pervaporation separation of the 1,5-PDO/IPA feed having a 9 : 1 weight ratio of components, the PDMS membrane prepared with a molar ratio of TEOS alkoxy groups to PDMS hydroxyl groups of 70 yielded a flux of 0.12 kg m⁻² h⁻¹ and separation factor of 17 638 at 40 °C. Long term stability analysis found that both hydrophilic (PVA) and organophilic (PDMS) membranes retained excellent pervaporation output over 18 days'' continuous exposure to the feed. Both the hydrophilic and organophilic membranes exhibited promising separation performance at elevated operating conditions, showing their great potential for purification of α,β and α,ω-diols.

The distillation-based purification of α,β and α,ω-diols is energy and resource intensive, as well as time consuming.     

Construction of a water-soluble and photostable rubropunctatin/β-cyclodextrin drug carrier

The purpose of the current study was to construct a β-cyclodextrin drug carrier for rubropunctatin to improve its water solubility and light stability for future cytotoxicity studies. The inclusion complexation behavior of rubropunctatin with β-cyclodextrin was investigated using FESEM, FT-IR and XRD. A molecular docking study was performed to elucidate the most probable inclusion structure. The inclusion complex could be completely dispersed in water and had a small size of 121.87 ± 2.13 nm (n = 3), a good PDI (0.320 ± 0.017), and an acceptable potential value of −27.7 ± 0.32 mV (n = 3). Furthermore, the stability of the rubropunctatin in water under light irradiation was found to be greatly enhanced after being encapsulated in cyclodextrin, and it exhibited a retention rate of over 70% vs. 10.17%. In addition, the cytotoxicity of the inclusion complex was evaluated by MTT assay and Annexin V-FITC/PI detection using cervical adenocarcinoma HeLa cells. The results showed that the inclusion complex had comparable toxicity compared to rubropunctatin solubilized with 0.4% DMSO. More importantly, the formation of the inclusion complex contributed greatly to the intensification of the bioavailability of rubropunctatin because the use of organic solvent was avoided.

The purpose of the current study was to construct a β-cyclodextrin drug carrier for rubropunctatin to improve its water solubility and light stability for future cytotoxicity studies.     

Nanoscopic insights into the surface conformation of neurotoxic amyloid β oligomers

Raman spectroscopy assisted by localized plasmon resonances generating effective hot spots at the gaps between intertwined silver nanowires is herein adopted to unravel characteristic molecular motifs on the surface of Aβ₄₂ misfolded oligomers that are critical in driving intermolecular interactions in neurodegeneration.

Unraveling characteristic structural determinants at the basis of Aβ₄₂ oligomers'' neurotoxicity by a sub-molecular SERS investigation of their surface.     

Direct access to multi-functionalized benzenes via [4 + 2] annulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes

An efficient [4 + 2] benzannulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes was achieved under metal-free reaction conditions selectively delivering a wide range of polyfunctional benzenes in high yields respectively (up to 94% yield).

An efficient [4 + 2] benzannulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes was achieved under metal-free reaction conditions selectively delivering a wide range of polyfunctional benzenes in high yields respectively (up to 94% yield).

Multi-substituted benzenes are privileged structural units ubiquitous in pharmaceuticals,¹ natural products² and advanced functional materials.³ Various excellent methodologies have been investigated for the construction of functionalized aromatics including nucleophilic or electrophilic substitution,⁴ transition metal-catalyzed coupling reactions⁵ and directed metalation.⁶ However, the widespread application of these strategies established thus far suffer from the limitations of functional groups introduced on the pre-existing benzene and regioselectivity issues. Among various synthetic methods, tandem benzannulation reactions arguably represent an attractive alternative to classical methods for rapid construction of polysubstituted benzenes in an atom-economical fashion.⁷ This protocol featuring an efficient transformation of acyclic building blocks into structurally valuable benzene skeletons. In this context, α-cyano-β-methylenones has been employed as substrates to format six-membered ring in tandem cyclization reactions due to the activation of the pronucleophile methyl group. In 2015, Tong and co-workers developed a phosphine-catalyzed addition/cycloaddition domino reactions of β′-acetoxy allenoate with 2-acyl-3-methyl-acrylonitriles to give 2-oxabicyclo[3.3.1]nonanes (Scheme 1a).⁸ Soon after that, the construction of benzonitrile derivatives and 1,3,5-trisubstituted benzenes via N-heterocyclic carbene catalysis has been reported by the groups of Wang and Ye independently (Scheme 1b).⁹ Then the synthesis of 1,3,5-trisubstituted benzenes by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-mediated annulation of α-cyano-β-methylenones and α,β-unsaturated carboxylic acids was also developed by Ye and co-workers (Scheme 1c).¹⁰ Shi et al. reported a base-promoted tandem cyclization reaction of α-cyano-β-methylenones and α,β-unsaturated enones, which have electron-withdrawing group (EWG), accessing to a wide range of benzonitriles in a different C–C bond formation process (Scheme 1d).¹¹ As part of our ongoing interest in harnessing enones for developing new methodologies for the construction of functionalized benzenes, we have recently demonstrated NHC-catalyzed convenient benzonitrile assembly in the presence of oxidant.^9a While the same reaction of enals and α-cyano-β-methylenones was conducted in the basic condition without NHC, a novel polyfunctionalized benzene product was obtained (Scheme 1e). The result inspired us to extend the synthetic potential of benzannulation strategy to access diverse benzonitriles, particularly from simpler, abundantly available starting materials.Open in a separate windowScheme 1α-Cyano-β-methylenones in cycloaddition domino reactions.At the outset, model reaction of 2-benzoyl-3-phenylbut-2-enenitrile 1a and cinnamaldehyde 2a was used to evaluate reaction parameters. Key results of condition optimization are summarized in 12 The configuration of products were assigned unambiguously by X-ray analysis of the product 3a. A quick solvent screening demonstrated that chloroform is the best choice to produce the benzannulation product 3a in a desirable yield (entries 10–13, †). Reducing the loading of the cinnamaldehyde or NaOH to 1.2 equivalence led to dramatical loss of the yield (entries 14 &15, EntryBaseSolventTime (h)Yield^b (%)1Cs₂CO₃Toluene24702Na₂CO₃Toluene24423K₂CO₃Toluene24384NaOHToluene12785NaOAcToluene24526KOHToluene12747K₃PO₄Toluene24588DBUToluene24339Et₃NToluene484610NaOHDCM1288 11 NaOH CHCI ₃ 12 94 12NaOHDCE128413NaOHH₂O48014^cNaOHCHCI₃128515^dNaOHCHCI₃128416^eNaOHCHCI₃1280Open in a separate window^aReaction conditions: 1a (0.1 mmol, 1.0 equiv.), 2a (0.15 mmol, 1.5 equiv.), base (0.2 mmol, 2.0 equiv.), and solvent (1 mL) for 12 h.^bIsolated yields.^c1a : 2a = 1 : 1.2.^dNaOH used 1.2 equiv.^e50 °C.Finally, the standard reaction conditions for the base-promoted synthesis of the multi-functionalized benzene derivatives identified as follows: 1.5 equivalence of NaOH and CHCl₃ as the solvent under an atmosphere of air for 12 hours at room temperature.With the optimized reaction conditions in hand, we explored the scope of the reaction. A series of enones were examined, variation of the electronic nature of the aromatic ring (R¹, including the substituted phenyl or thienyl) has little influence on the reaction efficiency (3b–f, 86–93% yields, Open in a separate window^aReaction conditions: 1a (0.1 mmol, 1.0 equiv.), 2a (0.15 mmol, 1.5 equiv.), NaOH (0.2 mmol, 2.0 equiv.), and CHCl₃ (1 mL) for 12 h.We next turned our attention to examine the scope of enals. Different substituents on the phenyl ring of cinnamaldehydes were tolerated even disregarding the position and properties, giving 4a–g in satisfying yields (82–92% yields, Open in a separate window^aReaction conditions: 1a (0.1 mmol, 1.0 equiv.), 2a (0.15 mmol, 1.5 equiv.), NaOH (0.2 mmol, 2.0 equiv.), and CHCl₃ (1 mL) for 12 h.To highlight the practicality of this mild and efficient method, the reaction of 2-benzoyl-3-phenylbut-2-enenitrile 1a at 4.0 mmol scale proceed well under the standard conditions to generate the desired product in 88% yield (Scheme 2).Open in a separate windowScheme 2Gram-Scale Synthesis of 3a.The formyl group could be easily reduced by using LiAlH₄ in THF at reflux, leading to the formation of the benzyl alcohol product 5 in 95% yield while keeping the CN group intact. Suzuki coupling of 3o with phenylboronic acid furnished derivative 6 in 90% yield¹³ (Scheme 3).Open in a separate windowScheme 3Synthetic transformation.To gain insight into the role of air in this reaction, a control experiment was designed and investigated (Scheme 4). When the reaction of 1a and 2a was carried out under an argon atmosphere, the desired product 3a was obtained in 10% yield and product 7 could be isolated in 82% yield. The results indicate that oxygen is necessary for the oxidation process and played a key role in this reaction.Open in a separate windowScheme 4Control experiment.A postulated reaction course is illustrated in Scheme 5. Briefly, α-deprotonation of enone 1a in the presence of bases, subsequent 1,4-addition of deprotonated enone I to enal 2a generates intermediate II, which undergoes an intramolecular aldol reaction to yield the adduct 7.¹⁴ Lastly, dehydration of 7 followed by spontaneous oxidative aromatization affords the polysubstituted benzonitrile 3a.Open in a separate windowScheme 5The proposed mechanism.     

Coordinated β-globin expression and α2-globin reduction in a multiplex lentiviral gene therapy vector for β-thalassemia

A primary challenge in lentiviral gene therapy of β-hemoglobinopathies is to maintain low vector copy numbers to avoid genotoxicity while being reliably therapeutic for all genotypes. We designed a high-titer lentiviral vector, LVβ-shα2, that allows coordinated expression of the therapeutic β^A-T87Q-globin gene and of an intron-embedded miR-30-based short hairpin RNA (shRNA) selectively targeting the α2-globin mRNA. Our approach was guided by the knowledge that moderate reduction of α-globin chain synthesis ameliorates disease severity in β-thalassemia. We demonstrate that LVβ-shα2 reduces α2-globin mRNA expression in erythroid cells while keeping α1-globin mRNA levels unchanged and β^A-T87Q-globin gene expression identical to the parent vector. Compared with the first β^A-T87Q-globin lentiviral vector that has received conditional marketing authorization, BB305, LVβ-shα2 shows 1.7-fold greater potency to improve α/β ratios. It may thus result in greater therapeutic efficacy and reliability for the most severe types of β-thalassemia and provide an improved benefit/risk ratio regardless of the β-thalassemia genotype.     

Optical and dielectric properties of NaCoPO4 in the three phases α, β and γ

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns. These compounds are crystallized in the orthorhombic, hexagonal and monoclinic system, in Pnma, P6₅ and P2₁/n space groups, respectively. The optical properties were measured by means of the UV-vis absorption spectrometry in order to deduce the absorption coefficient α and optical band gap E_g. The calculated values of the indirect band gaps (E_gi) for three samples were estimated at 4.71 eV, 4.63 eV and 3.8 for compounds α, β and γ, respectively. The Tauc model was used to determine the optical gap energy of the synthesized compounds. Then, the results of the dielectric proprieties measured by varying the frequency are described.

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns.     

Modulation of amyloid fibrillation of bovine β-lactoglobulin by selective methionine oxidation

Deposition of oxidation-modified proteins during normal aging and oxidative stress are directly associated with systemic amyloidoses. Methionine (Met) is believed to be one of the most readily oxidisable amino acid residues of protein. Bovine beta-lactoglobulin (β-lg), a model globular whey protein, has been presented as a subsequent paradigm for studies on protein aggregation and amyloid formation. Herein, we investigated the effect of t-butyl hydroperoxide (tBHP)-induced oxidation on structure, compactness and fibrillation propensity of β-lg at physiological pH. Notably, whey protein modification, specifically Met residues, plays an important role in the dairy industry during milk processing and lowering nutritional value and ultimately affecting their technological properties. Several bio-physical studies revealed enhanced structural flexibility and aggregation propensity of oxidised β-lg in a temperature dependent manner. A molecular docking study is used to predict possible interactions with tBHP and infers selective oxidation of methionine residues at 7, 24 and 107 positions. From our studies, it can be corroborated that specific orientations of Met residues directs the formation of a partially unfolded state susceptible to fibrillation with possible different cytotoxic effects. Our studies have greater implications in deciphering the underlying mechanism of different whey proteins encountering oxidative stress. Our findings are also important to elucidate the understanding of oxidation induced amyloid fibrillation of protein which may constitute a new route to pave the way for a modulatory role of oxidatively stressed proteins in neurological disorders.

This work reports selective methionine oxidation of β-lactoglobulin by tBHP reduces its thermal stability and enhances fibrillation propensity.     

Selection and Characterization of β-Lactam–β-Lactamase Inactivator-Resistant Mutants following PCR Mutagenesis of the TEM-1 β-Lactamase Gene

Mechanism-based inactivators of β-lactamases are used to overcome the resistance of clinical pathogens to β-lactam antibiotics. This strategy can itself be overcome by mutations of the β-lactamase that compromise the effectiveness of their inactivation. We used PCR mutagenesis of the TEM-1 β-lactamase gene and sequenced the genes of 20 mutants that grew in the presence of ampicillin-clavulanate. Eleven different mutant genes from these strains contained from 1 to 10 mutations. Each had a replacement of one of the four residues, Met69, Ser130, Arg244, and Asn276, whose substitutions by themselves had been shown to result in inhibitor resistance. None of the mutant enzymes with multiple amino acid substitutions generated in this study conferred higher levels of resistance to ampicillin alone or ampicillin with β-lactamase inactivators (clavulanate, sulbactam, or tazobactam) than the levels of resistance conferred by the corresponding single-mutant enzymes. Of the four enzymes with just a single mutation (Ser130Gly, Arg244Cys, Arg244Ser, or Asn276Asp), the Asn276Asp β-lactamase conferred a wild-type level of ampicillin resistance and the highest levels of resistance to ampicillin in the presence of inhibitors. Site-directed random mutagenesis of the Ser130 codon yielded no other mutant with replacement of Ser130 besides Ser130Gly that produced ampicillin-clavulanate resistance. Thus, despite PCR mutagenesis we found no new mutant TEM β-lactamase that conferred a level of resistance to ampicillin plus inactivators greater than that produced by the single-mutation enzymes that have already been reported in clinical isolates. Although this is reassuring, one must caution that other combinations of multiple mutations might still produce unexpected resistance.     

Metal-free hydrosulfonylation of α,β-unsaturated ketones: synthesis and application of γ-keto sulfones

γ-Keto sulfones are versatile building blocks and valuable intermediates in organic synthesis and pharmaceutical chemistry. Motivated by their excellent properties, we herein report a green, convenient, metal-free hydrosulfonylation method for a variety of ynones, vinyl ketones, and sodium sulfinates in the absence of stoichiometric oxidants. This operationally simple protocol provides straightforward and practical access to a wide range of γ-keto sulfones with broad functional group tolerance from easily available starting materials. Moreover, the β,γ-unsaturated keto sulfones could further react with 2,3-butadienoate to generate cyclopentenes in phosphine-mediated [3 + 2] cycloaddition.

The methodology features a convenient, mild, efficient, C–S sulfonylation approach without the use of any metal catalysts and stoichiometric oxidants.

As a useful common structural fragment in a broad number of pharmaceuticals¹ and functional materials,² keto sulfones are usually present in promising biologically active molecules such as Casodex,³VCAM-1 (ref. 4) and anti-HIV-1 (ref. 5) (Fig. 1). Furthermore, a valuable synthetic impression is associated with the role of reactive intermediates in various high-demand synthetic transformations,⁶ including total synthesis.⁷ Owing to their excellent properties, and efficient and practical synthesis methods keto sulfones are in high demand.Open in a separate windowFig. 1Representative biologically active γ-keto sulfones.In the past decades, a variety of protocols have been developed to construct β-keto sulfones.⁸ Whereas succinct synthetic routes toward structurally related γ-keto sulfones are scarce,⁹ traditionally, γ-keto sulfones were synthesized via the nucleophilic substitution of sodium sulfinates by 2-chlorovinyl ketones,¹⁰ the elimination of the bromo derivatives of saturated keto sulfones¹¹ and the oxidation of the corresponding sulfides or sulfoxides.¹² However, the principal drawback is that these procedures were strongly limited by multiple steps, narrow substrate scope, or poor stereoselectivity.Indeed, several streamlined strategies for the preparation of γ-keto sulfones involves addition reaction of alkenes or alkynes have been developed.¹³ Li''s group¹⁴ reported the synthesis of (E)-vinyl sulfones through Pd-catalyzed conjugate additions of alkynes with 1,2-bis(phenylsulfonyl)ethane. In 2013 Jiang and co-workers¹⁵ showed that a Pd-catalyzed sulfonylation of alkynoates with sodium sulfinates affords γ-keto sulfones (Scheme 1a). Li and coworkers¹⁶ reported that BPO triggered the hydrosulfonylation of chalcones with arylsulfonyl hydrazides producing γ-keto sulfones. Subsequently, Bi''s group¹⁷ developed a Ag₂CO₃-promoted sulfonylation of allyl/propargyl alcohols with sodium sulfinates for the preparation of γ-keto sulfones (Scheme 1b). Nevertheless, most cases still have to use large excess oxidants, noble metal catalysts, or require high temperatures. Accordingly, an efficient, mild and practical method to furnish γ-keto sulfones is worthwhile studying.Open in a separate windowScheme 1Methods for the synthesis of γ-keto sulfones.With growing demand for sustainable chemistry, an “ideal” reaction system for such transformations would be “metal-free” due to cost efficiency and possible advantages regarding toxicity, as well as selectivity. With this intent, we herein describe a simple and efficient acid-mediated sulfonylation of sodium sulfinates and α,β-unsaturated ketones for the selective synthesis of γ-keto sulfones (Scheme 1c). The significant advantages of this method are high efficiency, metal-free and mild reaction conditions, thus providing a potential application in natural product synthesis and medicinal chemistry.Further studies were commenced with the optimization of the conditions for the hydrosulfonylation of the ynone 1f with sodium benzosulfonate 2a (13e and acetyl chloride/H₂O,¹⁹ as used in the previous study, were completely ineffective due to several unknown complex products being formed (entry 1). Gratifyingly, the desired γ-keto sulfone 3fa was isolated in a 49% yield (E/Z = 90 : 10) as the major product for the reaction mediated by AcOH (entry 3). Encouraged by this initial result, we screened an array of acids. The results showed that 4-chlorobenzoic acid (PCBA) gave the best result, leading to the isolation of γ-keto sulfone 3fa in a yield of 80% (E/Z = 98 : 02) (entries 4–15). Solvent screening indicated that mesitylene could improve the yield to 85% (E/Z = 95 : 05) (entry 21). Further investigations on the reduced usage of PCBA to 2.0 equivalents, the yield of 3fa was slightly reduced (entry 22, 83% yield, E/Z = 95 : 05). The amounts of sodium benzosulfonate 2a and the reaction temperature have deleterious effects on the reaction yields (entries 23–27). Thus, the optimized reaction conditions were successfully established as 1f (1.0 equiv.), 2a (2.5 equiv.), PCBA (2.0 equiv.), and mesitylene (2.0 mL) at 30 °C in this process.Optimization of the reaction conditions^a

Enantioselective conjugate hydrosilylation of α,β-unsaturated ketones

Enantioselective conjugate hydrosilylation of β,β-disubstituted α,β-unsaturated ketones was realized. In the presence of a chiral picolinamide–sulfonate Lewis base catalyst, the reactions provided various chiral ketones bearing a chiral center at the β-position in up to quantitative yields with moderate enantioselectivities.

Enantioselective conjugate hydrosilylation of β,β-disubstituted α,β-unsaturated ketones was realized.

Chiral ketones are important intermediates for the synthesis of natural products or chiral drugs, and some themselves are useful chiral drugs.¹ Asymmetric conjugate reduction of α,β-unsaturated carbonyl compounds is an attractive and challenging transformation for the construction of chiral ketones. During the past few decades, many groups have devoted considerable efforts to this area and made great improvement, for instance, transition metal catalyzed asymmetric hydrogenation of α,β-unsaturated carbonyl compounds, including palladium,² iridium,³ copper,⁴ ruthenium,⁵ rhodium⁶ and cobalt.⁷ Besides, some organocatalyzed asymmetric conjugate transfer hydrogenations using Hantzsch ester⁸ or pinacolborane⁹ as the hydride source have also been reported. However, very few examples about chiral Lewis base catalyzed conjugate hydrosilylation of α,β-unsaturated carbonyl compounds have been reported and only chiral phosphine oxide Lewis base catalysts were used in these reactions (Scheme 1).¹⁰ Therefore, exploration of the application of other kinds of chiral Lewis base catalysts in this reaction is still highly desirable.Open in a separate windowScheme 1Enantioselective conjugate hydrosilylation of α,β-unsaturated ketones by chiral Lewis base catalysts.Recently, we developed a kind of easily accessible chiral picolinamide–sulfonate Lewis base catalysts and used them in asymmetric hydrosilylation of α-acyloxy-β-enamino esters,¹¹ one of them exhibiting excellent reactivity, diastereoselectivity and enantioselectivity. Herein we present the enantioselective conjugate hydrosilylation of β,β-disubstituted α,β-unsaturated ketones using this kind of Lewis base as catalysts, leading to various chiral ketones bearing a chiral center at β-position (Fig. 1).Open in a separate windowFig. 1Three typical chiral drugs containing chiral ketone moiety.First, various chiral Lewis base catalysts 2 were screened in the enantioselective hydrosilylation of (E)-1,3-diphenylbut-2-en-1-one 1a in acetonitrile at 0 °C. As shown in Fig. 2, l-piperazine-2-carboxylic acid derived N-formamide 2a,^12aR-(+)-tert-butylsulfinamide derived catalyst 2b^12b and picolinamide 2c^12c were found to be totally inactive for the reaction. Meanwhile picolinamide–tosylate catalyst 2d was highly active to afford the product with excellent yield in moderate ee value. Afterwards, several picolinamide–tosylate catalysts 2f–2h bearing electron-withdrawing group in 4-position of pyridine were employed in the reaction and 4-bromo picolinamide 2f delivered a slightly higher ee value. 5-Methoxy picolinamide 2i gave the product with the same ee value as that of 2d but in much lower yield. Lower enantioselectivities were observed with 4-phenyl picolinamide 2j and 3-methyl picolinamide 2k. When (R)-1-(2-aminonaphthalen-1-yl)naphthalen-2-ol derived catalyst 2l was used, no product was observed. When (1S,2R)-1-amino-2,3-dihydro-1H-inden-2-ol derived catalyst 2m gave the product in both poor yield and ee value. Moreover, two picolinamide–sulfonamide catalysts 2n and 2o were also used in the reaction and almost racemic products were obtained. Hence, 2f was determined as the optimal catalyst and was used through out our study.Open in a separate windowFig. 2Evaluation of the chiral Lewis base catalysts 2 in conjugate hydrosilylation of (E)-1,3-diphenylbut-2-en-1-one 1a. Unless otherwise specified, the reactions were carried out with 1a (0.1 mmol), trichlorosilane (0.2 mmol) and catalyst 2 (0.02 mmol) in 1 mL of acetonitrile at 0 °C for 24 hours. Isolated yield based on 1a. The ee values were determined by using chiral HPLC.Subsequently, the other reaction conditions were optimized. The results are summarized in Entry^aSolvent T (°C)Time [h]Yield^b [%]ee^c,d [%]1CH₃CN0247751 (R)2CH₃CH₂CN0248450 (R)3C₆H₅CN0248324 (R)4THF0249211 (R)51,4-Dioxane024635 (R)6CHCl₃0249225 (S)7CH₂Cl₂0249638ClCH₂CH₂Cl0249010 (R)9CCl₄0249535 (S)10Toluene0249555 (S)11Xylene024N.R.—12Mesitylene024N.R.—13C₆H₅CF₃0249531 (S)14Toluene−10489764 (S)15Toluene−20609265 (S)16Toluene−4072N.R.—Open in a separate window^aUnless otherwise specified, the reactions were carried out with 1a (0.1 mmol), trichlorosilane (0.2 mmol) and catalyst 2f (0.02 mmol) in 1 mL of solvent.^bIsolated yield based on 1a.^cThe ee values were determined by using chiral HPLC.^dThe absolute configuration of 3a was determined by comparison of the retention times of the two enantiomers on the stationary phase with those in the literatures.With the optimized conditions in hand, the scope and limitations of the reaction were explored. The results are summarized in Fig. 3. In the presence of 20 mol% of chiral Lewis base catalyst 2f and 2 equivalents of trichlorosilane, various α,β-unsaturated ketones were hydrosilylated. We first tested the effect of various 3-aryl groups of 1. 3-(4-Methoxy-phenyl) substrate 3e (Fig. 3) and 3-(naphthalen-2-yl) substrate 3i (Fig. 3) underwent the reaction to give the products with good yields in enantioselectivities close to 3a, while lower ee values were observed with 3b–3d, 3h, 3k and 3l (Fig. 3). No product was obtained with 3-(2-chloro-phenyl) substrate 3f and 3-(naphthalen-1-yl) substrate 3j, perhaps due to the high steric hindrance (Fig. 3). When 3-(2-methoxy-phenyl) substrate 3g was used, by prolonging the reaction time to 60 hours, the product was obtained with good yield but very poor enantioselection (Fig. 3). Trace amount of the product was detected with 3-(pyridin-2-yl) substrate 3m (Fig. 3). Next, some 3-phenyl-but-2-en-1-ones with different 1-aryl groups were also employed in the reaction. The 4-substituted or 3-substituted substrates delivered good yields of the products with similar or slightly lower enantioselectivities (Fig. 3), while much lower ee value was observed with 2-substituted substrate 3s (Fig. 3). For some other 3-alkyl chalcones, moderate to good yields and moderate ee values were obtained (Fig. 3), except for the bulkier tertiary butyl substituted 3w that gave trace amount of the product (Fig. 3). Reaction of 3y with two different 3,3-aryl groups afforded the product with moderate yield in very low enantioselectivity (Fig. 3). Finally, cyclic substrate 3z was subjected in the reaction and provided the product with excellent yield but in poor ee value (Fig. 3).Open in a separate windowFig. 3Substrate scope of the reaction. Unless otherwise specified, the reactions were carried out with 1 (0.1 mmol), trichlorosilane (0.2 mmol) and catalyst 2f (0.02 mmol) in 1 mL of toluene at −10 °C for 48 hours. Isolated yield based on 1. The ee values were determined by using chiral HPLC. The absolute configuration of 3a was determined by comparison of the retention times of the two enantiomers on the stationary phase with the literatures. The absolute configurations of other products were determined in analogy. ^aThe reaction time was 60 hours. ^bThe reaction time was 72 hours.Although detailed structural and mechanistic studies remain to be carried out, based on the absolute configuration of the product 3a, we propose a mechanism shown in Scheme 2. First, the nitrogen atom of the pyridine ring and the carbonyl oxygen atom of catalyst 2f are coordinated to Cl₃SiH to create an activated hydrosilylation species. Substrate 1a may approache the Cl₃SiH-catalyst complex to generate two transition states A and B. In transition state A, the N–H of catalyst 2f activates the carbonyl group of 1a through H-bonding. In addition, there could be π–π stackings between the two aromatic systems of the catalyst and the substrate. Then Si-face conjugate attack of the hydride to 1a generate (S)-product 3a. On the contrary, in transition state B through which (R)-product will be obtained, the carbonyl group of 1a can not be connected with the N–H of catalyst 2f. Thus the fact that (S)-enriched product 3a was obtained is consistent with the suggestion that the hydrosilylation predominantly proceeds through the pathway involving transition state A rather than transition state B.Open in a separate windowScheme 2A plausible reaction mechanism for hydrosilylation of 1a catalyzed by 2f.In conclusion, we have developed a facile, metal-free and mild enantioselective conjugate hydrosilylation of β,β-disubstituted α,β-unsaturated ketones. By using chiral picolinamide–sulfonate Lewis base as catalyst, the reactions provided various optically active ketones bearing a chiral center at β-position with moderate to good yields in moderate enantioselectivities. Comparing with the chiral phosphine oxide Lewis base catalysts, the chiral picolinamide–sulfonate is cheaper and easier accessible. The absolute configuration of one product was determined by comparison of the retention times of the two enantiomers on the stationary phase with those in the literature.     

Translation of β-Globin m-RNA in β-Thalassemia and the S and C Hemoglobinopathies

Genetic and biochemical evidence indicates that in beta-thalassemia there is impaired synthesis of the beta-globin chains of hemoglobin A. In patients heterozygous for the hemoglobinopathies, hemoglobin S and hemoglobin C, the mutant beta-chain is produced in smaller amounts than normal beta(A). Defective m-RNA translation has been suggested as a possible cause of decreased beta-globin polypeptide synthesis in thalassemia and the hemoglobinopathies. In the present study, the ribosomal assembly of beta-globin chains was examined in the peripheral, nucleated red blood cells and reticulocytes of patients with Cooley's anemia, thalassemia intermedia, sickle thalassemia, sickle cell anemia, hemoglobin C disease, and in hemolytic anemias not associated with a hemoglobinopathy. The translation times of beta(A), beta(S), and beta(C) did not differ significantly (average times; beta(A) = 75 sec, range 43-114, beta(S) = 69 sec, beta(C) = 92 sec). In thalassemia, no evidence was found for a delay in translation as the cause of the marked impairment of beta-globin synthesis. In several specimens of peripheral blood from thalassemic patients, the translation time of the beta-chain was even shorter than in nonthalassemic specimens (average time = 45 sec, range 35-59). The results suggest that the defect in beta-globin synthesis in beta-thalassemia is due to impaired initiation of beta-globin chain assembly or a quantitative deficiency in m-RNA.