The Lewis-acid-catalysed isomerisation of several derivatives of methyl 2,3-O-benzylidene-α-l-rhamnopyranoside and methyl 3,4-O-benzylidene-β-l-arabinopyranoside has been investigated. The presence of equatorial substituents vicinal to the benzylidene ring decreases the rate of isomerisation, ...

The syntheses are described of 2,3-di-O-glycosyl derivatives of methyl α-l- rhamnopyranoside (1–5)and α-d-mannopyranoside (6–9). Download full-size imageXYXY1α-l-Rha pα-d-Glc p6α-l-Rha pα-d-Glc p2α-d-Glc pα-l-Rha p7α-d-Man pα-d-Glc p3α-l-Rha pβ-d-Glc p8β-l-Fuc pβ-l-Fuc p4α-l-Rha...

Phytochemical investigation of Mimosa xanthocentra Mart. (Leguminosae: Mimosoideae), an herb comprising the diet of marsh deer and pampas deer in the Brazilian Pantanal, led to the isolation of flavones isovitexin-2″-O-α-l-rhamnopyranoside 1 and vitexin-2″-O-α-l-rhamnopyranoside 2, and a mix...

Hypertension is one of the major causes of mortality. Though a host of drugs are available for the treatment of hypertension, majority have been linked to adverse side effects, necessitating the need for research into natural compounds with fewer side effects. Kaempferol-7-O-α-L-rhamnopyroside ...

The syntheses are described of 2,3-di-O-glycosyl derivatives (1–12) of methyl α-l-rhamnopyranoside where the glycosyl moieties are variously α-l-fucopyranose, β-l-fucopyranose, β-d-glucopyranose, α-d-mannopyranose. The syntheses involve stereoselective glycosylation of methyl 4-O-benzoyl-3...

Open glycosylation of stannylated methyl β-d-galactopyranoside with per-O-benzoyl or -pivaloyl-glucopyranosyl bromide and -glucuronyl bromide, promoted by Ag-silica alumina, afforded regio- and stereoselectively glycosyl-β(1→6)-galactose and its orthoester derivative in good yield. Similar gl...

Reductive opening of the diphenylmethyl acetal in methyl 2,3-O-diphenylmethylene-α-l-rhamnopyranoside has been investigated by kinetic studies, and the results have been compared to those recently obtained by quantum chemical calculations. In contrast to the previous theoretical calculations wh...

Optically enriched homo-binuclear Fischer chromium carbene complexes with planar chiral arene chromium complexes gave α-allyl β-arylpropionates up to 97% ee by reaction with allyl alkoxide and subsequent photo-oxidative demetalation. The chiral hetero-binuclear tungsten carbene complexes affor...

Two series of novel polyimides (5a–g and 6a–g) containing flexible ether linkages and pendent trifluoromethyl (CF3) groups were synthesized from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (3a) and 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride (3b) with various CF3-substituted aromatic...

RésuméLa pureté énantiomérique de l'acide β-hydroxy β-trifluorométhyl β-phényl propionique, péparé par synthèse asymétrique, a été déterminée par RMN en présence d'un complexe chiral à l'europium. Sa configuration absolue a été établie par corrélation chimi...

Introduction of fluorine into polymers has been a subject of intense research as it brings about dramatic improvements in several properties of the polymers. Polymers containing fluorinated groups are endowed with solubility in organic solvents, lower dielectric constant and water uptake, higher...

Hepatocellular carcinoma is the fifth most common and the third most lethal cancer worldwide. In recent years, natural flavonoids have drawn great attention as repository for the exploitation of novel antineoplastic agents. 2′,4′-Dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC), a function...

Ga isomorphically substituted HZSM-5 and AlZSM-5 with different Si/Ga and Si/Al ratios were synthesized by a seed-induced hydrothermal in situ synthesis. This strategy significantly reduced organic templates in the synthesis process. Various techniques, including XRD, SEM, TEM, XRF, NMR, N2-sorp...

5-Methylcytosine (5mC), the major modified DNA base in mammalian cells, can be oxidized enzymatically to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) by the Ten-Eleven-Translocation (TET) family of proteins. Whereas 5fC and 5caC are recognized and removed...

Extinction is the learned inhibition of retrieval. It is the mainstay of exposure therapy, which is widely used to treat drug addiction, phobias and fear-related pathologies such as post-traumatic stress disorder. The serotonin (5-HT) system is positioned to modulate the extinction circuitry via...

Antibiotic resistance represents a major threat worldwide. Gram-positive and Gram-negative opportunistic pathogens are becoming resistant to all known drugs mainly because of the overuse and misuse of these medications and the lack of new antibiotic development by the pharmaceutical industry. Th...

An interesting iodine/methanol mediated rearrangement of tetraaylpiperidin-4-ones to 2-methoxy-2,4,5-triaryl-1H-pyrrole-3-ones is described. The structural features of the products are investigated by spectral data and single crystal X-ray analysis. The antifungal, antibacterial and antioxidant ...

The free energy difference (-ΔG0) for the axial-equatorial conformational equilibrium of spiro[2.5]octan-6-ol in CS2 has been found with the aid of PMR spectra taken at low temperatures, to be 0.79 kcal mole−1 at −75° C. An Arrhenius activation energy of ring inversion of 14.4 ± 1.3 kcal mole...

Conjugated copolymers were prepared from 2,7-di(thiophen-2-yl)phenanthrene-9,10-dione units with various polycyclic aromatic hydrocarbon moieties, namely, fluorene (PQF1-2), carbazole (PQC), and silafluorene (PQS). Employing mild condensation reaction conditions, PQF1-2 copolymers underwent post...

The pH sensitivity of polyaniline (PANI) membranes containing potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (KTFPB), potassium tetrakis(4-chlorophenyl)borate (KTpClPB), cesium carborane (Cs-carborane), tetradodecylammonium tetrakis(4-chlorophenyl)borate (TDATpClPB, ETH 500) or tridode...