Synthetic access toward the diverse ginsenosides

All the possible types of the protopanaxatriol and protopanaxadiol glycosides, the major active yet extremely heterogeneous principles of ginsengs, could be accessed by the present sequence of transformations, including global removal of the sugar residues from the crude ginseng extracts and stepwise elaboration of the glycans onto the aglycone. In particular, intramolecular hydrogen-bonding and neutral conditions have enabled glycosylation of the highly sterically hindered and acid labile dammarane C20-OH.