Reduction of 6/7-substituted 3-phenyltrop-3-en-2-ones: stereoselectivity and conformational analysis of the products

Reduction of 6/7-carboethoxy-3-phenyltrop-3-en-2-ones with H₂/Pd/C and NaBH₄ was studied in order to find a stereoselective route to the corresponding 3-phenyltropan-2-ones and 2α/2β-hydroxy-3-phenyltropanes. The 6/7-exo-carboethoxy-3-phenyltrop-3-en-2-ones were selectively reduced by Pd/C to 3β-phenyltropan-2-ones and 2α-hydroxy-3β-phenyltropanes. The corresponding 2β-hydroxy-3β-phenyl analogues were synthesized using NaBH₄, with a yield of 40%. Reduction of 6-endo-carboethoxy-3-phenyltrop-3-en-2-one yielded several products. The corresponding 7-endo-substituted analogue was selectively reduced with both Pd/C and NaBH₄ to 7-endo-carboethoxy-3β-phenyltropin-2-one. Analysis of stereochemically important ¹H NMR spectroscopy parameters was performed for all the products and used for conformational analysis in solution. X-ray analysis was performed for selected compounds.     

Structural revision of shatavarins I and IV, the major components from the roots of Asparagus racemosus

The two major steroidal saponins from the roots of Asparagus racemosus were isolated by RP-HPLC and their structure determined by extensive NMR studies. Their structures did not match those reported previously for shatavarins I and IV and were found to be 3-O-{[β-d-glucopyranosyl(1→2)][α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranosyl}-26-O-(β-d-glucopyranosyl)-(25S)-5β-furostan-3β,22α,26-triol and 3-O-{[β-d-glucopyranosyl(1→2)][α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranosyl}-(25S)-5β-spirostan-3β-ol.     

The α and β domains of human metallothionein-3 co-operatively protect against Aβ1-42-Cu2+ cytotoxicity

Cytotoxicity of A β with redox active metals in neuronal cells has been implicated in the progression of Alzheimer’s disease （AD）.Zn₇MT-3 protects cell against Aβ-Cu²⁺ toxicity.The roles of single domain proteins（α/β） andα-βdomain-domain interaction of Zn₇MT-3 in its anti-Aβ_1-42-Cu²⁺ toxicity activity were investigated herein.Aβ_1-42 and four mutants of human MT3 （α/βdomain,β（MT3）-α（MTl） and A31-34） were prepared and characterized.Aβ_1-42-Cu²⁺ induced hydroxyl radical and ROS production with/without Zn-MTs were measured by fluorescence spectroscopy and DCFH-DA in living cells,respectively.These results indicate that the two domains form a co-operative unit and each of them is indispensable in conducting its bioactivity.     

Justiciosides E-G, triterpenoidal glycosides with an unusual skeleton from Justicia betonica

Three new triterpenoidal glucosides, justiciosides E, F and G, were isolated from the aerial portion of Justicia betonica. Their structures were established through chemical and spectroscopic analyses, and showed an unusual A-nor-B-homo oleanan-12-ene skeleton type for the aglycone moiety as A-nor-B-homo-oleanan-10,12-diene-3β,11α,28-triol 28-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside, A-nor-B-homo-oleanan-10,12-diene-3β,11α,28-triol 28-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside, and 11α-methoxy-A-nor-B-homo-oleanan-10,12-diene-3β,11α,28-triol 28-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside, respectively.     

Ring size and substituent steric effects in cyclic ketene-N,O/S-acetal trifluoroacetylations

Trifluoroacetylations of cyclic ketene-N,O/S-acetals exhibit a ring size effect. The five-membered rings 2,4,4-trimethyl-2-oxazoline, 2-methyl-2-oxazoline, and 2-methyl-2-thiazoline, each form cyclic ketene-N,O/S-acetal intermediates which then react with trifluoroacetic anhydride to give β-monotrifluoroacetylation products. Conversely, the six-membered ring 2-methyl-2-oxazine gives its β,β-bistrifluoroacetylation product. In situ-generated five-membered ring N-Me cyclic ketene-N,O-acetals, 3,4,4-trimethyl-2-methylene-oxazolidine, and 3-methyl-2-methylene-oxazolidine, and six-membered ring 3-methyl-2-methylene-1,3-oxazinane were each β,β-bistrifluoroacetylated. However, 3-methyl-2-methylene-oxazolidine also afforded a γ-lactam by an iodide-catalyzed rearrangement of its β,β-bistrifluoroacetylated derivative. In situ-generated 3-methyl-2-methylene-thiazolidine gives both β-mono- and β,β-bistrifluoroacetylation products and no lactam, in contrast to its N,O-analog 3-methyl-2-methyleneoxazolidine.     

19-nor-11-Oxooleanan-12-ene and 18,19-seco-19-oxours-11,13(18)-diene triterpenes from Diospyros decandra bark

Four new triterpenes, 2α,3β-dihydroxy-19-nor-11-oxo-20-dimethylurs-12-en-24,28-dioic acid (equivalent to 2α,3β-dihydroxy-19-nor-11-oxoolean-12-en-24,28-dioic acid), 2α,3β-dihydroxy-18,19-seco-19-oxours-11,13(18)-dien-24,28-dioic acid, 2α,3β,19α-trihydroxy-11-oxours-12-en-24,28-dioic acid and 2α,3β,19α-trihydroxy-28-1′-β-d-[glucopyranosyl-(1″→6′)-glucopyranosyl]-urs-12-en-24,28-dioic acid were isolated from the methanol extract of the bark of Diospyros decandra as their acetate-methyl ester derivatives. The first two compounds represent the biosynthetic transformation products of 2α,3β,19-trihydroxyurs-24,28-dioic acid via oxidative rearrangement of ring E.     

Three New Myrsinol Diterpenes from <em>Euphorbia prolifera</em> and Their Neuroprotective Activities

Three new myrsinol diterpenes were isolated from the roots of Euphorbia prolifera. Their structures were elucidated as 2α-O-isobutyryl-3β,5α,7β,10,15β-penta-O-acetyl-14α-O-benzoyl-10,18-dihydromyrsinol (1), 2α-O-isobutyryl-3β-O-propion-yl-5α,7β,10,15β-tetra-O-acetyl-10,18-dihydromyrsinol (2), and 2α,14α-di-O-benzoyl-3β,5α,7β,10,15β-penta-O-acetyl-10,18-dihydromyrsinol (3) on the basis of spectroscopic data analyses (IR, ESI-MS, HR-ESI-MS, and 1D and 2D NMR). Their neuroprotective activities were evaluated and compounds 1 and 2 showed neuroprotective effects against MPP⁺-induced neuronal cell death in SH-SY5Y cells.     

Furostanol saponins with inhibitory action against COX-2 production from Tupistra chinensis rhizomes

Two furostanol saponins were obtained from the n-butanol fraction of methanol extract from Tupistra chinensis rhizomes,a folk medicine of Shennongjia Forest District of Hubei Province.Their structures were determined as (25S)-26-O-(β-D-glucopyranosyl)- furost-1β,3β,22α,26-tetrol-3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside (1) and (25R)- 26-O-(β-D-glucopyranosyl)-furost-1β,3β22α,26-tetrol 3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→2)-β-D-glu- copyranoside (2),on basis of chemical and spectroscopic evidences.1 and 2 displayed marked inhibitory action towards COX-2 production in macrophages of the rat abdomen induced by LPS at 20μg/mL.     

Seleno-β-lactams: synthesis of monocyclic and spirocyclic selenoazetidin-2-ones

An efficient protocol for the synthesis of novel seleno-β-lactams using operationally simple strategies is presented. 3-Phenyl/benzylseleno-β-lactams, obtained from 2-phenyl/benzylselenoethanoic acids, are transformed to cis-3-chloro-3-phenyl/benzylseleno-β-lactams, which undergo reaction with various active aliphatic and aromatic substrates catalyzed by Lewis acid to produce cis-3-alkoxy-3-phenyl/benzylseleno-β-lactams and C-3 monosubstituted seleno-β-lactams. Halogen mediated intraselenyl cyclization of cis-3-(prop-2-ynyloxy)-3-benzylseleno-β-lactams affords novel spiro seleno-β-lactams.     

Novel pseudo-morphotactic synthesis and characterization of tungsten nitride nanoplates

A novel pseudo-morphotactic transformation route was developed to synthesize polycrystalline β-W₂N nanoplates by thermally treating tungstate-based inorganic-organic hybrid nanobelts with a lamellar microstructure in an NH₃ flow. The tungstate-based hybrid nanobelts were formed in a water-in-oil-microemulsion-like “commercial H₂WO₄ powders/n-octylamine/heptane” reaction system. The as-obtained hybrid nanobelts were thermally treated in an NH₃ atmosphere at 650-800 °C for 2 h to form cubic β-W₂N nanoplates. XRD, SEM, TEM, FT-IR and TG-DTA were used to characterize the precursors and their final products. The polycrystalline β-W₂N nanoplates derived from hybrid nanobelts, with side lengths of several hundred nanometers, consist of small nanocrystals with an average grain size of 3.2 nm. The formation of β-W₂N nanoplates involved two steps: decomposing tungstate-based hybrid nanobelts into WO_y and W species and then nitridizing the active W-containing species to β-W₂N nanocrystals in an NH₃ flow. The platelike morphology of the β-W₂N nanocrystals was inherited from the precursor of tungstate-based inorganic-organic hybrid nanobelts.     

A new triterpene and a saponin from Centella asiatica

A new triterpene and a saponin,named 2α,3β,23-trihydroxyurs-20-en-28-oic acid(1)and 2α,3β,23-trihydroxyurs-20-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester(2),have been isolated from the aerial part of Centella asiatica.Their structures were elucidated by spectral methods,including 2D-NMR spectra.     

Two new olean-type triterpene fatty esters from Scorzonera mongolica

Two new triterpene fatty esters, 33-tetradecanoyl moradiol 1 and 3β-dodecanoyl moradiol 2, were isolated from Scorzonera mongolica. Their structures were elucidated as 3β-tetradecanoyloxy-28-hydroxylolean-18-ene and 3β-dodecanoyl-28-hydroxyl-olean-18-ene on the basis of IR, MS, ID NMR and extensive 2D NMR spectroscopic analyses.     

Stereoselective synthesis and Lewis acid mediated functionalization of novel 3-methylthio-β-lactams

A proficient etiquette for the stereoselective synthesis of novel 3-methylthio-β-lactams and their Lewis acid mediated functionalization is described. Treatment of 2-methylthioethanoic acid and appropriate imines in the Staudinger reaction leads to the stereocontrolled synthesis of novel trans-3-methylthio-β-lactams in excellent yields. cis-3-Chloro-3-methylthio-β-lactams, obtained from stereoselective chlorination of trans-3-methylthio-β-lactams using N-chlorosuccinimide (NCS) and AIBN, were subjected to Lewis acid (TiCl₄ or SnCl₄) mediated functionalization using various active aromatic, heterocyclic and aliphatic compounds (nucleophiles). This reaction provides an easy access to novel, stereoselective cis-3-monosubstituted-3-methylthio-β-lactams, which further undergo smooth desulfurization with Raney-nickel to afford C-3 cis- and trans-monosubstituted-β-lactams. The cis or trans configuration of the hydrogen/chloro/nucleophile substituent at C-3 was assigned with respect to C4–H.     

A novel simple pyrolytic approach towards anhydronucleosides

An interesting novel gas phase thermal intramolecular substitution reaction was discovered, which led to the conversion of the 2-β-d-N-glucosyl, 2-β-d-N-galactosyl and 2-β-d-N-ribosyl derivatives of 3-thioxo-2,3-dihydro-1,2,4-triazin-5(4H)-ones into their corresponding 3,2′-anhydro-β-d-mannosyl, 3,2′-anhydro-β-d-talosyl and 3,2′-anhydro-β-d-arabinosyl derivatives. The structures of these new anhydroglycosyls were determined by NMR experiments and by X-ray crystallography.     

First synthesis of 5,6-branched galacto-hexasaccharide,the dimer of the trisaccharide repeating unit of the cell-wall galactans of Bifidobacterium catenulatum YIT 4016

α-d-Galactopyranosyl-(1→6)-[β-d-galactofuranosyl-(1→5)]-β-d-galactofuranosyl-(1→6)-β-d-galactofuranosyl-(1→5)-[α-d-galactopyranosyl-(1→6)]-β-d-galactofuranose, the dimer of the trisaccharide repeating unit of the cell-wall galactans of Bifidobacterium catenulatum YIT 4016, has been synthesized as its dodecyl glycoside 2 by coupling of 2,3,4,6-tetra-O-benzyl-α-d-galactopyranosyl-(1→6)-[6-O-acetyl-2,3,5-tri-O-benzoyl-β-d-galactofuranosyl-(1→5)]-2-O-acetyl-3-O-benzyl-β-d-galactofuranosyl trichloroacetimidate 14 with dodecyl 2,3,4,6-tetra-O-benzyl-α-d-galactopyranosyl-(1→6)-[2,3,5-tri-O-benzoyl-β-d-galactofuranosyl-(1→5)]-2-O-acetyl-3-O-benzyl-β-d-galactofuranoside 16. The trisaccharide trichloroacetimidate donor 14 and trisaccharide acceptor 16 were regiospecifically prepared by employing 3-O-benzyl-1,2-O-isopropylidene-α-d-galactofuranose 4 as the glycosyl acceptor, and isopropyl 2,3,4,6-tetra-O-benzyl-1-thio-β-d-galactopyranoside 5 and 6-O-acetyl-2,3,5-tri-O-benzoyl-β-d-galactofuranosyl trichloroacetimidate 9 as glycosyl donors.     

The dynamic kinetic resolution of 3-oxo-4-phenyl-β-lactam by recombinant E. coli overexpressing yeast reductase Ara1p

Using a recombinant E. coli strain overexpressing yeast reductase Ara1p, we reduced racemic 3-oxo-4-phenyl-β-lactam to cis-(3S,4R)-3-hydroxy-4-phenyl-β-lactam as a single enantiopure product. The dynamic kinetic resolution occurred over the course of fermentation at pH 7. Under the same conditions, 3-oxo-4-(2-thiophenyl)-β-lactam 4 and 3-oxo-4-(2-furyl)-β-lactam 5 were not resolved.     

Four new norlignan glycoside isomers from the twigs of Cephalotaxus oliveri Mast.

Four novel isomers of norlignan glycoside were isolated from Cephalotaxus oliveri Mast.. Their structures were elucidated as 3S-4″-O-β-d-glucopyranosylnyasol 1, 3S-4′-O-β-d-glucopyranosylnyasol 2, 3S-4″-O-β-d-glucopyranosylhinokiresinol 3, 3S-4′-O-β-d-glucopyranosylhinokiresinol 4 by extensive spectroscopic methods including 1D and 2D NMR experiments (¹H, ¹³C, DEPT, ¹H–¹H COSY, HSQC, HMBC, ROESY) along with HR-ESIMS and comparison to literature data. Their absolute configurations were elucidated through CD spectra coupled with the quantum chemical CD calculations.     

On the ammonolysis of Ga2O3: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga2O3-GaN

We investigated the ammonolysis of β-Ga₂O₃ at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a β-Ga₂O₃ related oxynitride phase was found, and the nitrogen solubility in β-Ga₂O₃ was found to be below the detection limit of about 2-3 at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the β-Ga₂O₃ phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis.     

Chemical structure and biological activity of steroidal saponins from Furcraea gigantea

A new bisdesmosidic furostanol saponin, along with a known spirostanol saponin, furcreastatin, were isolated from Furcraea gigantea Vent. (Agavaceae). The structure of the new saponin was elucidated as 3-[(O-6-deoxy-α-L-mannopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1å 3)-O-[O-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranosyl)oxy]-(3β, 5α, 25R)-26-(β-D-glucopyranosyloxy)-22-hydroxyfurost-12-one. The structural identification was performed using a combination of spectroscopic techniques and chemical conversions. Furcreastatin showed a powerful haemolytic effect in the in vitro assay, but the new bisdesmosidic furostanol saponin demonstrated only a significant inhibition of the capillary permeability activity.     

Synthesis of the first per(3-deoxy)-cyclooligosaccharide: hepta(manno-3-deoxy-6-O-t-butyldimethylsilyl)-β-cyclodextrin

Reduction of hepta(manno-2,3-anhydro-6-O-t-butyldimethylsilyl)-β-cyclodextrin with lithium triethylborohydride gives hepta(manno-3-deoxy-6-O-t-butyldimethylsilyl)-β-cyclodextrin. This compound plus the hepta(2-O-methyl)- and hepta(2-O-benzyl)-derivatives all have the ⁴C₁ conformation. Capillary GC columns manufactured with hepta(manno-2,3-anhydro-, hepta(manno-3-deoxy-2-O-methyl- and hepta(manno-2-O-benzyl-6-O-t-butyldimethylsilyl)-β-cyclodextrin stationary phases were evaluated for enantio-discrimination with 39 non-polar racemic analytes. The GC column coated with the benzyl derivative showed enantioselectivity comparable to, and in some cases superior to, a commercial per(methyl)-β-cyclodextrin column. The other columns showed little or no enantio-discrimination. A thermodynamics study established a linear enthalpy–entropy compensation effect for two series of analytes on the commercial permethyl-β-cyclodextrin column, but not for the column coated with the benzyl derivative.