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 β-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 °C to room temperature and afforded the corresponding β-mannoside in high yield and satisfactory stereoselectivity. This reaction was applied to the total synthesis of acremomannolipin A and its analogue.