A novel approach to the synthesis of optically pure non protein α-amino acids in both L and D configurations from L-serine

Efficient syntheses of (2R)-2-Boc-amino-3-phenylsulfonyl-l-propanol 3 and its enantiomer 9 from L-serine are described. The potential of these compounds in a novel general method for the synthesis of optically pure non protein α-amino acids in both the L and D configurations is exemplified by the preparation of N-Boc-L-and D-homophenylalanine, -norvaline and -norleucine.     

Hydro(solvo)thermal synthesis and structural characterization of three lanthanide–carboxylate coordination polymers based on BDC and/or EDTA

Three lanthanide coordination polymers, [Ln₄(BDC)₆(H₂O)₂] _n (Ln = Er, 1; Ln = Tm, 2; BDC = 1,2-benzenedicarboxylate) and {[Nd₂(BDC)(EDTA)(H₂O)₂] · 1.5H₂O} _n , 3, were prepared by hydrothermal synthesis and characterized by elemental analysis, IR spectra, as well as single-crystal X-ray diffraction. The isostructural coordination polymers 1 and 2 exhibit four different coordination modes, which are rarely found in one lanthanide complex. Complex 3 displays a 2-D wave-like network assembled by two polycarboxylate ligands.     

Diastereoselective synthesis of β- and γ2-muurolene: a carbocationic pathway from mono- to sesquiterpenes

The Lewis acid catalysed addition of the piperityl chlorides6 to isoprene yields adduct7, which undergoes a cis-stereoselective cyclisation to give the diastereoisomeric muurolene monohydrochlorides8. Treatment with potassium tert-butoxide affords β- and γ₂- muurolene 2.     

A novel metal-free synthesis of thiazole-substituted α-hydroxy carbonyl compounds and 2-alkenylthiazoles from thiazole N-oxides and olefins

A metal-free and highly atom-economic synthesis of thiazole-substituted α-hydroxy carbonyl compounds has been developed. Catalyzed by 5 mol% of p-toluenesulfonic acid (TsOH), a variety of thiazole-substituted α-hydroxy carbonyl compounds were obtained in moderate to good yields via 1,3-dipolar cycloaddition of thiazole N-oxides with olefins, followed by a ring-opening reaction. Furthermore, the corresponding 2-alkenylthiazoles could be produced in excellent yields from synthesized α-hydroxy carbonyl compounds through a one-pot, two-step dehydration process.     

Psiguamers A–C,three cytotoxic meroterpenoids bearing a methylated benzoylphloroglucinol framework from Psidium guajava and total synthesis of 1 and 2

Three sesquiterpene-based meroterpenoids psiguamers A–C (1–3) with new skeletons were isolated from Psidium guajava leaves. Compounds (±)-1 and (±)-2 were two pairs of humulene-derived meroterpenoids bearing a rare methylated benzoylphloroglucinol unit, while 3 was an unprecedented adduct of bicyclogermacrene and methylated benzoylphloroglucinol. Their structures were determined based on comprehensive analyses of spectroscopic data, calculated electronic circular dichroism (ECD) spectra, total synthesis, and X-ray crystallographic data. The biomimetic synthesis of (±)-1 and (±)-2 was achieved. Compound (+)-1 exhibited cytotoxic activities against five human tumor cell lines (HCT-116, HepG2, BGC-823, A549, and U251), with IC₅₀ values of 2.94, 9.01, 6.45, 5.42, and 5.33 μmol/L, respectively.     

Synthesis of novel optically pure quinolyl-β-amino alcohol derivatives from 2-amino thiophenol and chiral α-acetylenic ketones and their IBX-mediated oxidative cleavage to N-Boc quinolyl carboxamides

A methodology directed toward the stereoselective synthesis of novel quinolyl glycines is presented. This strategy is based on the cyclocondensation reaction between 2-amino thiophenol 4 and chiral acetylenic ketones of the type 3 containing a latent α-amino acid functionality. The initially formed benzo[b][1,4]thiazepine derivatives 5, readily undergo sulphur extrusion in refluxing toluene to yield the corresponding 2,4-disubstituted quinolines 6. Subsequent oxazolidine ring opening followed by in situ re-protection of the amino group afforded the corresponding quinolyl-β-amino alcohols 8a–8f in enantiomerically pure form and good overall yields. The derivatives 8 are in principle suitable precursors for the synthesis of novel optically pure quinolyl glycines through oxidation of the alcohol side chain. However, these amino alcohol derivatives 8, did not afford the expected quinolyl glycines 10 using numerous oxidising agents and reaction conditions. Instead, by reacting 8 with the mild oxidising reagent IBX 11, an oxidative CC cleavage leading to the N-Boc quinolyl carboxamides 12 took place.     

Copper-catalyzed synthesis of N-aryl acridones from 2-amino benzophenones and aryl boronic acids via sequential double oxidative C–N coupling

Pot-economic synthesis of N-aryl acridones was performed with 2-aminobenzophenones and aryl boronic acids as starting materials. Cu-catalyzed chelation-assisted oxidative C–N cross-coupling reactions were well merged with the following intra-molecular oxidative dehydrogenative C–H amination reactions under an air atmosphere. The use of reagent capsules can further resolve the compatibility problem of reagents and simplify the operational process, providing a more straightforward access to the target products.     

Retraction Note to: Nano Pt–TiO2 for an efficient one-pot photocatalytic synthesis of quinaldines from anilines and ethanol

Research on Chemical Intermediates - This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1007/s11164-020-04374-7     

Methodology fro the polyene and related antibiotics--enantiospecific synthesis of chiral structural units of amphotericin B from A common progenior: the C1–C13 polyol segment

The optically pure C₁–C₁₃ subunit of amphotericin B encompassing five asymmetric centers was synthesized from a readily available chiron derived from L-glutamic acid.     

A novel synthesis of aryl methyl sulfones and β-hydroxysulfones from sodium sulfinates and di-tert-butyl peroxide in H2O medium

A novel and convenient synthetic route for aryl methyl sulfones and β-hydroxysulfones was developed via the radical reaction between sodium sulfinates and di-tert-butyl peroxide (DTBP). Without any catalysts and additives, the synthetic process could be smoothly carried out to afford the target products in good to excellent yields in H₂O medium, demonstrating its promising application. In the present system, H₂O could act not only as a green solvent but also as a reactant.     

A novel synthesis of 3-((benzo[d]thiazol-2-ylamino)(phenyl)methyl)-4-hydroxy-1-methylquinolin-2(1H)-one via consecutive C–C and C–N bond formation in water

Research on Chemical Intermediates - A simple, efficient, and eco-friendly protocol has been developed for the synthesis of novel...     

A convenient CeCl3·7H2O/NaI-promoted synthesis of structurally novel and strained tricyclic β-lactams from hydrazines

A convenient synthetic protocol for structurally novel and strained highly derivatized tricyclic β-lactams has been developed. The synthesis involves CeCl₃·7H₂O/NaI catalyzed addition-condensation of mercaptoacetic acid and N-aroyl-N′-arylidenehydrazines followed by intramolecular cyclodehydration to afford bicyclic 5H-thiazolo[4,3-b][1,3,4]-oxadiazoles, which on treatment with acid chlorides in the presence of triethylamine furnish highly derivatized tricyclic 3H-azetidino[2,1-b]-thiazolo[3,4-d][1,3,4]-oxadiazol-6-ones in 80-93% yields. The process presents an excellent illustration of Ce(III)-catalyzed C-C, C-N and C-S bond formation in a one-pot procedure.     

Hydrothermal synthesis and structural characterization of novel α-Keggin unit-supported Cu(II)- and Mn(II)-bipyridine complexes from a <Emphasis Type="Italic">tri</Emphasis>-lacunary precursor

Blue [{Cu(2,2′-bipy)₂}₂{α-SiW₁₂O₄₀}] (bipy = bipyridyl) (1) and pale yellow [Mn(2,2′-bipy)₃]₂[α-SiW₁₂O₄₀] (2) have been synthesized hydrothermally and characterized by IR spectroscopy and single crystal X-ray structure analysis. In 1, the [α-SiW₁₂O₄₀]⁴⁻ ion acts as a bridge between the two [{Cu(2,2′-bipy)₂]²⁺ moieties via coordination through the terminal oxygen atoms, while in 2, the [Mn(2,2′-bipy)₃]²⁺ ion balances the charge on the polyoxo anion without forming any covalent bond. To the best of our knowledge, this is the first example of transition metal-mediated transformation of [α-SiW₉O₃₄]¹⁰⁻ to [α-SiW₁₂O₄₀]⁴⁻. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dianionic complexes with hexacoordinate silicon(IV) or germanium(IV) and three bidentate ligands of the salicylato(2–) type: Syntheses and structural characterization in the solid state and in solution

Reaction of tetramethoxysilane or tetramethoxygermane with salicylic acid and morpholine (molar ratio 1:3:2) in tetrahydrofuran yielded morpholiniummer-tris[salicylato(2–)-O¹,O³]silicate(mer -5) and morpholiniummer-tris[salicylato(2–)-O¹,O³]germanate (mer-8), respectively. Treatment of tetramethoxysilane with 5-chlorosalicylic acid and piperidine (molar ratio 1:3:2) in tetrahydrofuran afforded piperidinium mer-tris[5-chlorosalicylato(2–)-O¹,O³]silicate–ditetrahydrofuran (mer-6·2THF). Triethylammonium mer-tris[3-methylsalicylato(2–)-O¹,O³]silicate (mer-7) was obtained analogously by reaction of tetramethoxysilane with three molar equivalents of 3-methylsalicylic acid and two molar equivalents of triethylamine in dichloromethane/diethyl ether. The racemic compounds mer-5, mer-6· 2THF,mer-7, and mer-8 were characterized by elemental analyses (C, H, N), single-crystal X-ray diffraction, as well as solid-state (²⁹Si) and solution(¹H, ¹³C, ²⁹Si) NMR studies. The structural characterizationwas complemented by computational studies (HF studies, TZVP level) of thefac- and mer-tris[salicylato(2–)-O¹,O³]silicatedianion. In addition, the behavior of mer-7 in solution was studied by VT ¹HNMR experiments.     

A one-pot synthesis of 4-aryl-2-methyl-1,2,3,4-tetrahydro-γ-carbolines from 5-aryloxazolidines and indoles via a Mannich/Friedel–Crafts sequence

Benzaldehydes react smoothly with the nonstabilized azomethine ylide derived from sarcosine and formaldehyde to form 5-aryloxazolidines, which undergo ring-opening to give 2-(indol-3-ylmethylamino)-1-arylethanols in 69–79% yields on reaction with indoles in acetic acid. Their subsequent acid-catalyzed cyclization into 4-aryl-2-methyl-1,2,3,4-tetrahydro-γ-carbolines was performed in polyphosphoric acid in moderate yields. The latter can also be prepared directly from 5-aryloxazolidines and indoles in polyphosphoric acid.     

A novel UPLC–MS/MS method for simultaneous quantification of trigonelline, 4-hydroxyisoleucine,and diosgenin from Trigonella foenum-graecum extract: Application to pharmacokinetic study in healthy and type 2 diabetic rats

Trigonelline (TR), 4-hydroxyisoleucine (4-HI), and diosgenin (DG) are the main bioactives of the purified standardized extract of the popular plant Trigonella foenum-graecum L. (TFG), and it has been proven effective for the treatment of various diseases. However, to the best of our knowledge, no study has investigated the pharmacokinetic parameters of purified standardized T. foenum-graecum extract in normal and diabetic Wistar rats. The present study has developed and validated a rapid, reliable, and sensitive simultaneous ultra-performance liquid chromatography MS method to estimate these bioactives. The chromatographic separation was achieved using methanol, acetonitrile, and 0.1% formic acid with the ideal gradient flow system on a BEH Shield RP 18 column. A positive electrospray ionization mode was selected to estimate m/z values of TR (138.14 > 94.63), 4-HI (148.19 > 74.08), and DG (415.54 > 271.33). The method was robust and reproducible over the linearity range of 60–5000, 6–5000, and 15–5000 ng/mL for TR, 4-HI, and DG, respectively. Using this novel validated method, we investigated the pharmacokinetic parameters of bioactives using Phoenix WinNonlin version 8.0 (Certera) in normal and diabetic rats. The assay was successfully applied for the estimation of pharmacokinetic parameters using noncompartmental analysis. This investigation shows that the absorption rate increased, whereas distribution and elimination processes slowed down in diabetic rats compared with normal rats.     

Preparation and characterization of H3−2(x+y)MnxCoyPMo12O40 heteropolysalts. Application to adipic acid green synthesis from cyclohexanone oxidation with hydrogen peroxide

H_3−2(x+y)Mn_xCo_yPMo₁₂O₄₀ heteropolysalts (x + y ≤ 3/2 and x, y: 0–1.5) were prepared by a cationic exchange method based on barium sulfate precipitation. Structural and textural properties of salts were examined by several physicochemical techniques such as infrared, scanning electron microscopy-energy dispersive X-ray, and ³¹P nuclear magnetic resonance spectroscopies, X-ray diffraction diffraction, and thermogravimetric analysis, and their catalytic properties were evaluated in the cyclohexanone oxidation using hydrogen peroxide (30%). The reaction products, adipic, glutaric, succinic, hexanoic, 6-hydroxyhexanoic, 7,7-dimethoxy, and heptanoic acids and 1,1-dimethoxy octane were identified by gas chromatography–mass spectrometry analysis. Only adipic, glutaric, and succinic acids were quantified by chromatography (high-performance liquid chromatography), the other products were noted X. Adipic acid (AA) is the major product for all systems. The effects of molar ratios of catalyst/reactant and cyclohexanol/cyclohexanone, heteropolysalt composition, and reaction duration on AA yield were investigated. The stability of the catalytic system was also examined. H_3−2(x+y)Mn_xCo_yPMo₁₂O₄₀ catalysts were found to be efficient for the cyclohexanone oxidation with conversions >95%. Among them, H₁Mn_0.25Co_0.75 exhibits the highest AA yield (75%).     

Synthesis and characterization of Ni0.7−xMnxZn0.3Fe2(C4H2O4)3·6N2H4 (x = 0.1–0.6): A precursor for the synthesis of nickel–manganese–zinc ferrites

Journal of Thermal Analysis and Calorimetry - Spinel ferrites are the technologically important materials whose application ranges from the environmental, bio-medical to the smart devices. The...     

Access to the structures of fluoromagnesium compounds: synthesis and structural characterization of the β-diketiminato magnesium fluoride [{CH(CMeNAr)2}Mg(μ-F)(THF)]2·toluene

β-Diketiminato magnesium fluoride [{CH(CMeNAr)₂}Mg(μ-F)(THF)]₂·toluene (Ar=2,6-i-Pr₂C₆H₃, 2·toluene) was synthesized. The molecular structure of 2 revealed for the first time, the double fluoro bridge feature between the two magnesium atoms with a typical MgF bond length (average 1.95 Å).