Construction of β-Mannosidic Bonds via Gold(I)-Catalyzed Glycosylations with Mannopyranosyl ortho-Hexynylbenzoates and Its Application in Synthesis of Acremomannolipin A

A mild and convenient protocol for direct synthesis of beta-mannosides has been developed. Glycosylation of 4,6-O-benzylidene-protected mannosyl ortho-hexynylbenzoates with various alcohol acceptors catalyzed by gold(I) complex proceeded smoothly at 0 degrees C to room temperature and afforded the corresponding beta-mannoside in high yield and satisfactory stereoselectivity. This reaction was applied to the total synthesis of acremomannolipin A and its analogue.