Glycosylidene Carbenes. Part 25. Glycosidation of ginkgolides B and A

Weber, Martin; Vasetla, Andrea

doi:10.1002/hlca.19970800808

Cited by 8 publications

(4 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Weber and Vasella prepared glucosides of ginkgolide B by the reaction with glucosylidene diazirines [59]. The 1-O-and 10-O-glucosylated ginkgolides B 53 ± 57 ( Fig.…”

Section: Figs 4 and 8)mentioning

confidence: 99%

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

Bernet

Vasella

2000

HCA

View full text Add to dashboard Cite

The interpretation of 1H‐NMR chemical shifts, coupling constants, and coefficients of temperature dependence (δ(OH), J(H,OH), and Δδ(OH)/ΔT values) evidences that, in (D6)DMSO solution, the signal of an OH group involved as donor in an intramolecular H‐bond to a hydroxy or alkoxy group is shifted upfield, whereas the signal of an OH group acting as acceptor of an intramolecular H‐bond and as donor in an intermolecular H‐bond to (D6)DMSO is shifted downfield. The relative strength of the intramolecular H‐bond depends on co‐operativity and on the acidity of OH groups. The acidity of OH groups is enhanced when they are in an antiparallel orientation to a C−O bond. A comparison of the 1H‐NMR spectra of alcohols in CDCl3 and (D6)DMSO allows discrimination between weak and strong intramolecular H‐bonds. Consideration of IR spectra (CHCl3 or CH2Cl2) shows that the rule according to which the downfield shift of δ(OH) for H‐bonded alcohols in CDCl3 parallels the strength of the H‐bond is valid only for alcohols forming strong intramolecular H‐bonds. The combined analysis of J(H,OH) and δ(OH) values is illustrated by the interpretation of the spectra of the epoxyalcohols 14 and 15 (Fig. 3). H‐Bonding of hexopyranoses, hexulopyranoses, alkyl hexopyranosides, alkyl 4,6‐O‐benzylidenehexopyranosides, levoglucosans, and inositols in (D6)DMSO was investigated. Fully solvated non‐anomeric equatorial OH groups lacking a vicinal axial OR group (R=H or alkyl, or (alkoxy)alkyl) show characteristic J(H,OH) values of 4.5 – 5.5 Hz and fully solvated non‐anomeric axial OH groups lacking an axial OR group in β‐position are characterized by J(H,OH) values of 4.2 – 4.4 Hz (Figs. 4 – 6). Non‐anomeric equatorial OH groups vicinal to an axial OR group are involved in a partial intramolecular H‐bond (J(H,OH)=5.4 – 7.4 Hz), whereas non‐anomeric equatorial OH groups vicinal to two axial OR form partial bifurcated H‐bonds (J(H,OH)=5.8 – 9.5 Hz). Non‐anomeric axial OH groups form partial intramolecular H‐bonds to a cis‐1.3‐diaxial alkoxy group (as in 29 and 41: J(H,OH)=4.8 – 5.0 Hz). The persistence of such a H‐bond is enhanced when there is an additional H‐bond acceptor, such as the ring O‐atom (43 – 47: J(H,OH)=5.6 – 7.6 Hz; 32 and 33: 10.5 – 11.3 Hz). The (partial) intramolecular H‐bonds lead to an upfield shift (relative to the signal of a fully solvated OH in a similar surrounding) for the signal of the H‐donor. The shift may also be related to the signal of the fully solvated, equatorial HO−C(2), HO−C(3), and HO−C(4) of β‐D‐glucopyranose (16: 4.81 ppm) by using the following increments: −0.3 ppm for an axial OH group, 0.2 – 0.25 ppm for replacing a vicinal OH by an OR group, ca. 0.1 ppm for replacing another OH by an OR group, 0.2 ppm for an antiperiplanar C−O bond, −0.3 ppm if a vicinal OH group is (partially) H‐bonded to another OR group, and −0.4 to −0.6 for both OH groups of a vicinal diol moiety involved in (partial) divergent H‐bonds. Flip‐flop H‐bonds are observed between the diaxial HO−C(2) and HO−C(4) of the inositol 40 (J(H...

show abstract

“…Weber and Vasella prepared glucosides of ginkgolide B by the reaction with glucosylidene diazirines [59]. The 1-O-and 10-O-glucosylated ginkgolides B 53 ± 57 ( Fig.…”

Section: Figs 4 and 8)mentioning

confidence: 99%

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

Bernet

Vasella

2000

HCA

View full text Add to dashboard Cite

show abstract

“…[141] To increase the water solubility of ginkgolides, Weber and Vasella synthesized glycosylated ginkgolide analogues. [142,143] Glycosidation was carried out by reaction of ginkgolides with a glycosylidene-derived diazirine to give a large number of glycosylated analogues. Intra-and intermolecular bonds of these analogues, as well as the parent ginkgolides, were studied by 1 H NMR spectroscopic analysis.…”

Section: Synthetic Modification Of Parent Compoundsmentioning

confidence: 99%

Chemistry and Biology of Terpene Trilactones fromGinkgo Biloba

2004

View full text Add to dashboard Cite

Ginkgo biloba, the ginkgo tree, is the oldest living tree, with a long history of use in traditional Chinese medicine. In recent years, the leaf extracts have been widely sold as phytomedicine in Europe and as a dietary supplement worldwide. Effects of Ginkgo biloba extracts have been postulated to include improvement of memory, increased blood circulation, as well as beneficial effects to sufferers of Alzheimer's disease. The most unique components of the extracts are the terpene trilactones, that is, ginkgolides and bilobalide. These structurally complex molecules have been attractive targets for total synthesis. Terpene trilactones are believed to be partly responsible for the neuromodulatory properties of Ginkgo biloba extracts, and several biological effects of the terpene trilactones have been discovered in recent years, making them attractive pharmacological tools that could provide insight into the effects of Ginkgo biloba extracts.

show abstract

“…DMSO kann in bestimmten Testsystemen Probleme bereiten,140 jedoch sind derartige Effekte nicht generell zu beobachten 141. Um die Wasserlöslichkeit der Ginkgolide zu erhöhen, synthetisierten Weber und Vasella glycosylierte Ginkgolid‐Derivate 142. 143 Durch Glycosidierung der Ginkgolide mit einem von Glycosyliden abgeleiteten Diazirin wurde eine große Zahl glycosylierter Analoga erhalten.…”

Section: Synthesestudienunclassified

Chemie und Biologie von Terpentrilactonen ausGinkgo biloba

Strømgaard¹,

Nakanishi

2004

Angewandte Chemie

View full text Add to dashboard Cite

Ginkgo biloba – der Ginkgobaum – ist die älteste lebende Baumart der Welt. Ginkgo‐Präparate sind ein wichtiger Bestandteil in der traditionellen chinesischen Medizin, und in den letzten Jahren haben die Blattextrakte als Phytopräparat in Europa und als Nahrungsergänzungsmittel weltweit breiten Absatz gefunden. Zu den postulierten Wirkungen des Ginkgo‐biloba‐Extrakts gehören die Verbesserung der Gedächtnisleistung, die Steigerung der Blutzirkulation und eine Verzögerung der Alzheimer‐Demenz. Was den Extrakt so einzigartig macht, sind die Terpentrilactone – Ginkgolide und Bilobalid –, die als strukturell komplexe Moleküle attraktive Zielstrukturen für Totalsynthesen waren. Es wird angenommen, dass Terpentrilactone für die neuroregulatorischen Eigenschaften der Ginkgo‐biloba‐Extrakte mit ausschlaggebend sind. Eine Reihe biologischer Wirkungen der in den letzten Jahren entdeckten Terpentrilactone macht diese zu aussichtsreichen pharmakologischen Substanzen.

show abstract

Glycosylidene Carbenes. Part 25. Glycosidation of ginkgolides B and A

Cited by 8 publications

References 32 publications

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

Chemistry and Biology of Terpene Trilactones fromGinkgo Biloba

Chemie und Biologie von Terpentrilactonen ausGinkgo biloba

Contact Info

Product

Resources

About