合成路线1

Peracetylation of (I) to yield (II), followed by treatment with thiophenol and boron trifluoride, afforded the mannopyranoside (III). After methanolysis of the acetate esters of (III) in the presence of NaOMe, the resultant tetrahydroxy derivative (IV) was protected as the bis-acetonide (V) by treatment with 2,2-dimethoxypropane and 10-camphorsulfonic acid. The phenylsulfanyl group of (V) was reductively removed by means of lithium and a catalytic amount of naphthalene, yielding the dihydropyran derivative (VI). The free hydroxyl group of (VI) was then esterified with Ac2O in pyridine to give (VII). Addition of sodium azide to dihydropyran (VII) in the presence of cerium ammonium nitrate furnished the azido nitrate (VIII). The nitrate ester of (VIII) was then selectively cleaved by means of sodium nitrite, giving alcohol (IX), which was further protected by silylation with tert-butyldimethylsilyl chloride and imidazole to provide silyl ether (X). Subsequent alcoholysis of the acetate ester group of (X) in the presence of NaOMe provided the key intermediate (XI).