A-Rhamnopyranosides

Monocyclic Carotenoids.—Aphanizophyll (26) is a new carotenoid glycoside, probably a rhamnopyranoside. It is thus a 4-hydroxy-derivative of myxoxan-thophyll, which might be considered as an intermediate in the formation of 2 -hydroxyflexixanthin (27). However, the presence of flexixanthin (28) and its deoxy-derivative (29) suggests an alternative biogenesis. 

Catalano, G., Fossen, T., Andersen, 0.M., Petunidin 3-0-a-rhamnopyranoside-5-0- 3-gluco-pyranoside and other anthocyanins from flowers of Vida villosa, J. Agric. Food Chem., 1998, 46, 4568 570. 

Q-3-O-p-glucuronopyranoside in the berries of V. vitis-idaea, and unambiguously confirm the structures of Q-3-O-[4"-(3-hydr03g -3-methyl-glutaroyl)]-ot-rhamnopyranoside, Q-3-O-a-rhamnopyranoside, Q-3-O-p-galactopyranoside, Q-3-O-a-arabinofuranoside, Q-3-0-p-3g lopyranoside and Q-3-O-a-arabinopyranoside. 

Our initial studies were directed towards the synthesis and characterization of phenylboronate esters derived from methyl 6-deoxy-/ -D-allopyranoside, methyl a-L-rhamnopyranoside, methyl -L-fucopyranoside, and methyl 6-deoxy-/ -D-glucopyranoside. Previous work (14) in this laboratory indicated that the reaction of triphenylboroxole and methyl... 

Reaction of methyl a-L-rhamnopyranoside with triphenylboroxole gave a syrupy boronate ester which was characterized as a crystalline phenyl-carbamate. Removal of the phenylboronic acid residue gave a product identified as methyl a-L-rhamnopyranoside 4-N-phenylcarbamate, since it was identical with that resulting from removal of the ketal group from methyl 2,3-O-isopr opylidene-a-L-rhamnopyranoside 4-N-phenylcarbamate (12). This establishes the structure of the original ester as methyl a-L-rhamnopyranoside 2,3-phenylboronate (24). 

Ethyl 2,3,4-tri-O-acetyl-l-thio-a-L-rhamnopyranoside was synthesized by applying the reported method based on the BF3-Et20-catalyzed reaction of ethane... 

Fig. 21.—Partial 13C-N.m.r. Spectrum of the Rhamnomannan (16) of Sporothrix schenckii, with Shift Comparisons with Signals of Methyl a-D-Mannopyranoside (Lower Inset Lines) and Methyl a-L-Rhamnopyranoside (Upper Inset Lines). (Solvent, D20 temperature, 33° chemical shifts expressed as 8C, relative to external tetramethyl-silane.)...

Four independent conformations were found in the asymmetric unit cell (see Fig. 3), but their superposition showed that all shared the same global shape (see Fig. 4), albeit with slightly different conformations for the externally placed L-rhamnopyranosyl-(1 3)-(9-a-L-rhamnopyranoside moiety. The internal trisaccharide subunit, L-rhamnopyranosyl-(l 2)-(9-)S-D-glucopyranosyl-(1 2)-0-/l-D-... 

The reaction of nitroethane/sodium ethoxide with the dialdehyde (31), obtained by periodate oxidation of methyl a-L-rhamnopyranoside (30), leads after deionization to a sirupy mixture (32), which was shown by thin-layer chromatography to contain five main components together with traces of other substances. After acetylation one di-O-acetate (33) crystallized from the mixture and was isolated in 12.5% 5deld, based on the rhamnoside (30). Reduction ot (33) with lithium aluminiumhydride gave methyl 3-C-methyl-3-amino-3,6-dideoxy-a-L-glucopyranoside (34), which was additionally characterized as the triacetate (35)... 

After having assembled the D-C precursor the a-(l->3)-attachment of the E unit was to be performed by the NIS method. Therefore a favorable access to the L-olivomycal was needed. We had previously prepared this compound by a five step route from -arabinose ( ). Recently an advantageous preparation of and its epimer Ij-mycaral ( ) by treatment of methyl 2,3-0-benzylidene o-Jj-rhamnopyranoside (35) with methyllithium, was worked out ( ). ... 

SCHEME 5. Richardson s application of the Fischer nitromethane cyclization to the sugar dialdehyde derived from periodate cleavage methyl a-L-rhamnopyranoside (1961). 

Yadava, R.N. and Reddy, V.M.S., A new flavone glycoside, 5-hydroxy-7,3, 4, 5 -tetramethoxy-flavone 5-0-(3-D-xylopyranosyl(l 2)-a-L-rhamnopyranoside from Bauhinia variegata Linn., J. Asian Nat. Prod. Res., 3, 341, 2001. 

All sugars are 0-substituted unless specified as C-glycosides rhamnoside, a-L-rhamnopyranoside glucoside, p-D-glucopyranoside arabinose is as specified. Pr, prenyl. StemB, stem bark Aerial, aerial parts Whole, whole plant Rhiz, rhizome. 

Yadava, R.N., Mathews, S.R., and Jain, N., Naringenin 4 -0-a-L-rhamnopyranoside, a novel flavanone glycoside from the stem of Crotalaria striata D.C., J. Indian Chem. Soc., 74, 426, 1997. 

Rhamnoside, a-L-rhamnopyranoside apioside, p-apiofuranoside glucoside, p-D-glucopyranoside galactoside, P-d-galactopyranoside xyloside, p-D-xylopyranoside glucuronide, p-D-glucuronopyranoside. Cinnamic acids are assumed to be in the -form. 

Saxena, V.K. and Singal, M., Genistein 4 -0-a-L-rhamnopyranoside from Pithecellobium dulce, Fitoterapia, 69, 305, 1998. 

Licania pittieri Prance is a tree up to 15 meters high growing in the cloud forests at 1800 m in altitude. From the methanol extract of the leaves, collected in the Parque Nacional Henry Pittieri, oleanolic acid (1), ursolic acid (2), catechin (3), epicatechin (4), quercetin (5), and four glycosidic derivatives, quercetin 3-O-P-D-galactopyranoside (6), quercetin 3-O-P-D-glucopyranoside (7), quercetin 3-O-a-L-rhamnopyranoside (8), and quercetin 3-O-a-L-arabinopyranoside (9) were identified directly by comparing their spectroscopic data with those reported in the literature and/or authentic samples [see Fig. (1)] [5]. 

Successively from the chloroform-methanol and methanol extracts also some flavonoids were obtained kaempferol 3-0-a-L-rhamnopyranoside (31), quercetin 3-0-a-L-rhamnopyranoside (8), myricetin 3-O-a-L-rhamnopyranoside (32), myricetin 3-0-(2"-0-(3-D-xylopyranosyl)-a-L-... 

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