n-Octyl α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside derivatives from the glandular trichome exudate of Geranium carolinianum.

Chemical investigation of the glandular trichome exudate from Geranium carolinianum L. (Geraniaceae) led to the characterization of unique disaccharide derivatives, n-octyl 4-O-isobutyryl-α-L-rhamnopyranosyl-(1→2)-6-O-isobutyryl-β-D-glucopyranoside (1), n-octyl 4-O-isobutyryl-α-L-rhamnopyranosyl-(1→2)-6-O-(2-methylbutyryl)-β-D-glucopyranoside (2) and n-octyl 4-O-(2-methylbutyryl)-α-L-rhamnopyranosyl-(1→2)-6-O-isobutyryl-β-D-glucopyranoside (3), named caroliniasides A-C, respectively. These structures were determined by spectral means. n-Alkyl glycoside derivatives have been isolated from the glandular trichome exudates for the first time. This rare type of secondary metabolites could be applicable to chemotaxonomic perspective because they are found in glandular trichome exudates of plants belonging to the genus Geranium, according to our studies.