Search results for "RESONANCE"
showing 10 items of 6625 documents
Functionalization of Bambusurils by a Thiol-Ene Click Reaction and a Facile Method for the Preparation of Anion-Free Bambus[6]urils
2018
Sulfide-functionalized bambus[4]urils ((RS)8 BU[4]) and bambus[6]urils ((RS)12 BU[6]) were synthesized through thiol-ene click coupling reactions (TEC) of allylbambus[n]urils. Thiosugars were grafted to BU[4] and BU[6]. Synthesis of BU[6] derivatives always requires the use of a template anion (iodide, chloride, or bromide), which is enclosed in the cavity of BU[6]. We show that this anion influences the reactivity of bambus[6]urils. An encapsulated iodide makes allyl functions of allyl12 BU[6] less reactive towards TEC and hydrogenation reactions in comparison to the corresponding chloride or bromide inclusion complexes. This is critical for the chemical reactivity of BU[6] and even more t…
Cycloartane Glycosides from Three Species of Astragalus (Fabaceae)
2011
Nine cycloartane-type glycosides were isolated from three species of the genus Astragalus (Fabaceae): From the aerial parts of A. cicer L., two new saponins, cicerosides A and B (1 and 2, resp.), i.e., a tetradesmosidic and tridesmosidic cycloartane-type glycosides besides one known compound, from the roots of A. sempervirensLam., one known saponin, and from the roots of A. ptilodesBoiss. var. cariensisBoiss., five known compounds. Their structures were established mainly by 600-MHz 2D-NMR techniques (1H,1H-COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectroscopy.
Self-Assembled Polymers Based on bis-Tetra-Urea Calix[4]arenes Connected via the Wide Rim
2008
Six double calixarenes were synthesised in which two tetra-urea calix[4]arenes are linked by a rigid spacer between the urea functions at their wide rim. The dimerisation of their tetra-urea parts leads to hydrogen-bonded polymeric assemblies in apolar solvents. The addition of the stoichiometric amount of a tetra-tosylurea calix[4]arene disrupts the polymeric structures due to the preferred formation of heterodimeric capsules between tetra-aryl and tetra-tosylurea calix[4]arenes. The existence of polymeric assemblies was further established by AFM studies on spin-coated samples.
Foetidissimosides C–F, Novel Glycosides from the Roots ofCucurbita foetidissima
2004
Two novel echinocystic acid (=(3β,16α)-3,16-dihydroxyolean-12-en-28-oic acid) glycosides, foetidissimosides C (1), and D (2), along with new cucurbitane glycosides, i.e., foetidissimosides E/F (3/4) as an 1 : 1 mixture of the (24R)/(24S) epimers, were obtained from the roots of Cucurbita foetidissima. Their structures were elucidated by means of a combination of homo- and heteronuclear 2D-NMR techniques (COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC), and by FAB-MS. The new compounds were characterized as (3β,16α)-28-{[O-β-D-glucopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-6-deoxy-α-L-mannopyranosyl-(12)-α-L-arabinopyranosyl]oxy}-16-hydroxy-28-oxoolean -12-en-3-yl β-D-glucopyranosiduronic acid (1…
Bafouoside C, a new triterpenoid saponin from the roots of Cussonia bancoensis Aubrev. & Pellegr.
2014
Abstract A new triterpenoid saponin named bafouoside C 3-O-β- d -glucopyranosyl-(1 → 4)-[β- d -galactopyranosyl-(1 → 2)]-β- d -glucuronopyranosyloleanolic acid 28-O-β- d -glucopyranosyl ester; (1), together with five known compounds 3-O-β- d -galactopyranosyl-(1 → 2)-β- d -glucuronopyranosyloleanolic acid (2), 23-hydroxyursolic acid (3), 28-O-α- l -rhamnopyranosyl-(1 → 4)-O-β- d -glucopyranosyl-(1 → 6)-O-β- d -glucopyranosyl-23-hydroxyursolic acid (4), 3-O-β- d -glucopyranosyl-23-hydroxyursolic acid (5), and 3-O-α- l -arabinopyranosyl-23-hydroxyursolic acid (6), were isolated from the roots of Cussonia bancoensis Aubrev. & Pellegr. Their structures were established on the basis of 1D- and 2…
Spirostane and cholestane glycosides from the bulbs of Allium nigrum L
2011
Abstract A phytochemical investigation of the fresh bulbs of Allium nigrum L. led to the isolation of new spirostane-type glycosides as two inseparable isomer mixtures, nigrosides A1/A2 (1a/1b) and nigrosides B1/B2 (2a/2b), two new cholestane-type glycosides, nigrosides C and D (3 and 4), together with the known compounds, 25(R,S)-5α-spirostan-2α,3β,6β-trio1-3-O-β- d -glucopyranosyl-(1 → 2)-O-[β- d -xylopyranosyl-(1 → 3)]-O-β- d -glucopyranosyl-(1 → 4)-β- d -galactopyranoside (5a/5b) and 25(R,S)-5α-spirostan-2α,3β,6β-trio1 3-O-β- d -glucopyranosyl-(1 → 2)-O-[4-O-(3S)-3-hydroxy-3-methylglutaryl-β- d -xylopyranosyl-(1 → 3)]-O-β- d -glucopyranosyl-(1 → 4)-β- d -galactopyranoside (6a/6b), isola…
Structural and functional models for the dinuclear copper active site in catechol oxidases
2003
Two new mu-methoxo-bridged dinuclear copper(II) complexes with a N-substituted sulfonamide, [Cu(mu-OMe)(L)(NH(3))](2) (1) and [Cu(mu-OMe)(L)(DMSO)](2) (2) [HL, N-2-(4-methylbenzothiazole)benzenesulfonamide], have been prepared and characterized by single-crystal X-ray difraction analyses. Compound 1 crystallizes in the monoclinic space group C(2)/c with a=22.0678(18), b=7.9134(7), c=21.1186(18)A, beta=113.788(4) degrees and Z=8. Compound 2 crystallizes in the monoclinic space group C(2)/c with a=18.0900(10), b=9.5720(10), c=24.2620(10) A, beta=98.7120(10) degrees and Z=8. In both complexes the copper atoms have square-planar environments bridged by two oxygen atoms from methoxide groups. Ma…
Foetidissimosides C—F, Novel Glycosides from the Roots of Cucurbita foetidissima.
2004
Two novel echinocystic acid (=(3β,16α)-3,16-dihydroxyolean-12-en-28-oic acid) glycosides, foetidissimosides C (1), and D (2), along with new cucurbitane glycosides, i.e., foetidissimosides E/F (3/4) as an 1 : 1 mixture of the (24R)/(24S) epimers, were obtained from the roots of Cucurbita foetidissima. Their structures were elucidated by means of a combination of homo- and heteronuclear 2D-NMR techniques (COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC), and by FAB-MS. The new compounds were characterized as (3β,16α)-28-{[O-β-D-glucopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-6-deoxy-α-L-mannopyranosyl-(12)-α-L-arabinopyranosyl]oxy}-16-hydroxy-28-oxoolean -12-en-3-yl β-D-glucopyranosiduronic acid (1…
New Acylated Saponins fromPolygala myrtifolia
2003
The ten new acylated presenegenin (=(2β,3β,4α)-2,3,27-trihydroxyolean-12-ene-23,28-dioic acid) glycosides 1–10 have been isolated by successive MPLC from the roots of Polygala myrtifolia L. as five inseparable mixtures of the trans- and cis-4-methoxycinnamoyl derivatives, i.e., myrtifoliosides A1/A2 (1/2), B1/B2 (3/4), C1/C2 (5/6), D1/D2 (7/8), and E1/E2 (9/10). Their structures were elucidated mainly by extensive spectroscopic experiments, including 2D NMR techniques, as 3-O-(β-D-glucopyranosyl)presenegenin 28-{O-β-D-galactopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-[D-apio-β-D-furanosyl-(13)]-O-α-L-rhamnopyranosyl-(12)-O-[α-L-arabinopyranosyl-(13)]-4-O-(trans-4-methoxycinnamoyl)-β-D-fucopy…
New Acylated Triterpene Saponins fromPolygala arenaria
2003
Eight new acylated triterpene saponins 1–8 were isolated from the roots of Polygala arenaria as four inseparable (E)/(Z) mixtures of the 4-methoxycinnamoyl and 3,4-dimethoxycinnamoyl derivatives by repeated MPLC over silica gel. Their structures were established mainly by 600-MHz 2D-NMR techniques (1H,1H-COSY, TOCSY, NOESY, HSQC, HMBC) as 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-galactopyranosyl-(14)-O-[β-D-glucopyranosyl-(13)]-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-{4-O-[(E)-4-methoxycinnamoyl]}-β-D-fucopyranosyl) ester and its (Z)-isomer (1/2), 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-galactopyranosyl-(14)-O-[β-D-glucopyranosyl-(13)]-O-β-D-xylopyranosyl-(14)-O-α-L…