Synthesis of l-arabinose-containing fragments of the oat root saponin Avenacin A-1

Mukhopadhyay, Balaram; Field, Robert A.

doi:10.1016/j.carres.2004.02.021

Cited by 10 publications

(4 citation statements)

References 15 publications

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“…The 3 J H1,H2 value of the anomeric proton of methyl-α- l -arabinoside decreased from 6.9 to 4.9 Hz after a 2- O -glucosyl linkage was added. Interestingly, when the steric hindrance is particularly strong, due to a bulky 1- O -aglycone, the observed 3 J H1,H2 value could reach low values similar to those observed with a β-configuration (around 2–3 Hz). ,, Therefore, it appears that in the case of 2- O -linked arabinopyranosides an intermediate or low value of the coupling constant does not permit the accurate assignment of the configuration of the anomeric proton.…”

Section: Resultsmentioning

confidence: 90%

“…Interestingly, when the steric hindrance is particularly strong, due to a bulky 1-O-aglycone, the observed 3 J H1,H2 value could reach low values similar to those observed with a β-configuration (around 2À3 Hz). 12,23,24 Therefore, it appears that in the case of 2-O-linked arabinopyranosides an intermediate or low value of the coupling constant does not permit the accurate assignment of the configuration of the anomeric proton. Furthermore, it is important to note that almost all the natural 3-O-arabinosylated flavonoids are reported with an R-L-arabinosyl moiety.…”

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confidence: 99%

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Quercetin and Kaempferol 3-O-[α-l-Rhamnopyranosyl-(1→2)-α-l-arabinopyranoside]-7-O-α-l-rhamnopyranosides from Anthyllis hermanniae: Structure Determination and Conformational Studies

et al. 2011

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The study reports the isolation and structural identification of two new flavonol triglycosides from the methanolic extract of Anthyllis hermanniae, exhibiting the same glycosylation pattern: quercetin 3-O-[α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside]-7-O-α-L-rhamnopyranoside (1) and kaempferol 3-O-[α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside]-7-O-α-L-rhamnopyranoside (2). A conformational study related to the central arabinoside moiety was carried out including the analysis of the contribution of NOE effects and acetylation to the elucidation of the 2-O-linked arabinoside configuration of the anomeric carbon. We also report the total synthesis of a model compound, quercetin 3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside (3), which verifies the structures of the isolated compounds.

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Section: Resultsmentioning

confidence: 90%

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confidence: 99%

Quercetin and Kaempferol 3-O-[α-l-Rhamnopyranosyl-(1→2)-α-l-arabinopyranoside]-7-O-α-l-rhamnopyranosides from Anthyllis hermanniae: Structure Determination and Conformational Studies

et al. 2011

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“…Qin and A. Osbourn, unpublished data) and/or the products of enzymatic digestion of avenacin A-1 with a microbial hydrolase can serve as acceptor substrates for GT enzyme assays. In addition to natural substrates, synthetic substrates based on benzoic acid are also available and are being used to study the regioselectivity of these GTs (Mukhopadhyay and Field, 2004).…”

Section: Establishing a Function For Candidate Gtsmentioning

confidence: 99%

Saponin Glycosylation in Cereals

2006

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Triterpene saponins are glycosylated plant secondary metabolites that are common in dicotyledonous species but rare in monocots. These compounds are antimicrobial and are important for plant defence. They also have a variety of pharmaceutical and industrial applications. Oat (Avena spp.) produces triterpene saponins called avenacins, specialised metabolites that are not represented in other cereals. The avenacins are synthesised and stored in roots and provide protection against soil-borne fungal pathogens. Glycosylation is often critical for bioactivity of saponins. We are using a combination of mutant analysis, database mining, expression profiling and functional characterisation to identify glycosyltransferases required for addition of sugar units to avenacins. By identifying the molecular machinery required for avenacin biosynthesis we hope to understand the broader elements of the evolution of specialised metabolic pathways.

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“…lycopersici. 15 Continuing our efforts 16 on synthesis of oligosaccharide components of saponins important for plant defence mechanisms, we describe herein the chemical synthesis of branched methyl lycotetraoside 2. The flexibility of the route described offers potential for construction of lycotetraose analogues.…”

Section: Introductionmentioning

confidence: 99%

Efficient synthesis of methyl lycotetraoside, the tetrasaccharide constituent of the tomato defence glycoalkaloid α-tomatine

2005

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Branched oligosaccharide lycotetraose, beta-D-glucopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranose, is a key constituent of many steroidal saponins, including glycoalkaloid alpha-tomatine, which is involved in protection of plants from invading pathogens. A new synthesis of the methyl beta-lycotetraoside () is described. Key steps of the synthesis include two successive glycosylation reactions of disaccharide acceptor methyl (4,6-O-benzylidene-3-O-p-methoxybenzyl-beta-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D-galactopyranoside with readily available benzoylated trichloroacetimidates of alpha-D-glucopyranose and alpha,beta-D-xylopyranose. This scheme allows sequential glycosylation in one-pot on account of the convenient in situ removal of a p-methoxybenzyl protecting group under the acid conditions of the first glycosylation step. Following deprotection, tetrasaccharide was obtained in 19% yield over eight steps.

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Synthesis of l-arabinose-containing fragments of the oat root saponin Avenacin A-1

Cited by 10 publications

References 15 publications

Quercetin and Kaempferol 3-O-[α-l-Rhamnopyranosyl-(1→2)-α-l-arabinopyranoside]-7-O-α-l-rhamnopyranosides from Anthyllis hermanniae: Structure Determination and Conformational Studies

Quercetin and Kaempferol 3-O-[α-l-Rhamnopyranosyl-(1→2)-α-l-arabinopyranoside]-7-O-α-l-rhamnopyranosides from Anthyllis hermanniae: Structure Determination and Conformational Studies

Saponin Glycosylation in Cereals

Efficient synthesis of methyl lycotetraoside, the tetrasaccharide constituent of the tomato defence glycoalkaloid α-tomatine

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