Reinvestigation of absolute stereostructure of (-)-rosiridol: structures of monoterpene glycosides, rosiridin, rosiridosides A, B, and C, from Rhodiola sachalinensis

Three new (-)-rosiridol glycosides, rosiridosides A, B, and C, were isolated from the roots of Rhodiola sachalinensis together with rosiridin (-)-rosiridol 1-O-beta-D-glucopyranoside]. In the course of the structure elucidation of those new glycosides, the absolute configuration of the 4-position in (-)-rosiridol was reinvestigated. On the basis of the application of the modified Mosher's method for (-)- and (+)-rosiridol derivatives, the absolute configuration of the 4-position in (-)-rosiridol should be revised to be S orientation from the recently assigned R form, so that the absolute stereostructures of rosiridosides A, B, and C and rosiridin were determined.