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L-Rhamnose is widely distributed in many plant families, where it occurs either alone as in quercetin, associated with D-glucose or D-galactose as in rutin or robinin, or as rhamnobioses in heterosides such as alaternin, xanthorhamnin and catharticin.NMR spectroscopy, both proton' and 13C2-4, has played an important role in determining the structure of the aglycone in flavonoids but it is more difficult to identify the sugar sequence, the point of attachment of the oligosaccharide to the aglycone and the position of the interglycosidic linkages.L-Rhamnose is also found in structural units of bacterial capsular polysa~charides,~.~ e.g. Streptococcus, Pneumococcus and Klebsiella. In studies concerned with their antigenic behaviour, and with the synthesis or analysis of immunodominant fragments, it is important to know the exact carbohydrate structures involved. For these reasons we have described the synthesis and NMR parameters of several di-and tri-saccharides containing L-rhamnose. This paper compares the proton and I3C NMR values of L-rhamnose (1) and three a-rhamnobioses, 0 -a -L-rhamnopyranosyl-( 1 -+ 2) -L-rhamnopyranose (2) and the (1 -+ 3) (3) and (1 -+ 4) (4) isomers (Fig. 1). Application of the data tabulated here has permitted the complete elucidation of the structure of a xanthorhamnin (Fig. 2) and, also, the decision to be made between two possible structures of an oligosaccharide obtained by bacteriophage degradation of the capsular polysaccharide in Klebsiella serotype K32.

The structure of echinacoside, isolated from Echinacea angustifolia D.C. (Asteraceae) roots has been determided by 1H-NMR-and 13C-NMR-spectra to be β-(3′,4′-dihydroxyphenyl)-ethyl-O-α-ʟ-rhamnopyranosyl (1 → 3)-O-β-ᴅ-[β-ᴅ-glucopyranosyl (1 → 6)]-(4-O-caffeoyl)-glucopyranoside (cf. Fig. 1).