Efficient Synthesis of Lupane-Type Saponins via Gold(I)-Catalyzed Glycosylation with Glycosyl ortho-Alkynylbenzoates as Donors

Glycosylation of the acid labile betulin and betulinic acid derivatives was achieved with glycosyl ortho-hexynyibenzoates as donors under the catalysis of PPh3AuNTf2; this enabled the efficient synthesis of lupane-type saponins, as exemplified by the total synthesis of the proposed betulinic acid trisaccharide from Bersama engleriana.