A Highly Efficient Approach To Construct (epi)-Podophyllotoxin-4-O-glycosidic Linkages as well as Its Application in Concise Syntheses of Etoposide and Teniposide.

By taking full advantage of the mild promotion conditions of an ortho-alkynylbenzoate glycosylation protocol, a highly efficient approach to construct the challenging (epi)-podophyllotoxin 4-O-glycosidic linkages was devised under the activation of a catalytic amount of a Au(I) complex. The novel method enjoys a quite broad substrate scope in terms of both glycosyl donors and podophyllotoxin derivative acceptors, providing the desired glycosides in excellent yields. Based on the new approach, concise syntheses of clinically used anticancer reagents etoposide and teniposide were accomplished, and the overall yields counting from easily available starting materials could reach as high as 18% and 9%, respectively.