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A mixture of glycosidic acids, each of which consisted of a tetrasaccharide unit linked by an anomeric carbon to I lhydroxypal~nitic acid and containing short-chain fatty acids ester-linked to the sugar units, was isolated from Ipotnoeu stalls. Basic hydrolysis allowed isolation of a single compound whose structure was determined by two-dimensional NMR methods to be (S)-1 I-hydroxypalmitic acid 11-0-~-quinovopyranosy1-(1-4)-a-rhamnopyranosyl-(1,2)-~-glycopyranosyl-( I-2)-P-quinovopyranoside. Further HPLC separation of the original mixture allowed separation of a compound that was shown, by 2D NMR, to have 2-methylbutanoic acid molecules linked to C-4 of the terminal quinovose and C-2 of rhamnose, 3-hydroxy-2-methyl butanoic acid linked to C-6 of glucose, and with the palmitic acid forming a lactone at C-3 of rhamnose. Closer inspection revealed that this compound was actually a mixture of diastereomers involving different ((2R.3R) and (2S,3S)) enantiomers of 3-hydroxy-2-methylbutanoic acid bonded to the chiral tetrasaccharide core. Key ~~r r l s :tetrasaccharide, two-dimensional NMR. A partir de l'lpomoea stons, on a isole un melange d'acides glycosidiques qui contiennent chacun une unite tetrasaccharide like par un carbone anomerique a I'acide 1 1-hydroxypalmitique et qui contiennent des esters d'acides gras a chaines plus courtes lies a des unites de sucre. De leur hydrolyse basique on a pu isoler qu'un seul compose dont on a determine la structure par des mtthodes de RMN bidimensionnelles; il s'agit du 11-0-P-quinovopyranosyl-(1,4)-arhamnopyranosyl-(l,2)-~-glucopyranosyl-(1,2)-~-quinovopyranoside de l'acide (S)-1 1 -hydroxypalmitique. Une separation plus poussee du melange original par CHLP a permis de separer un compose qui, selon la RMN en 2D, contiendrait des molCcules d'acide 2-m6thylbutanoique likes au C-4 du quinovose terminal et au C-2 du rhamnose, de I'acide 3-hydroxy-2-mCthylbutanoique lie au C-6 du glucose et de I'acide palmitique formant une lactone en C-3 du rhamnose. Un examen plus minutieux a rCvClC que ce compose est en realite un melange de diastCrCoisombres impliquant differents ((2R,3R) et (2S,3S)) Cnantiomeres de l'acide 3-hydroxy-2-methylbutanoique lies a un noyau tetrasaccharide chiral.

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