合成路线1

Deoxy rhamnopyranoside derivative (I) was acetylated to (II) and subsequently reacted with thiophenol in the presence of boron trifluoride etherate to afford the phenylthio glycoside (III). Acetate hydrolysis of (III) with methanolic K2CO3 gave alcohol (IV). Inversion of the configuration of position 4 to provide the required epimeric alcohol (VII) was achieved via conversion of (IV) to triflate (V), followed by displacement with potassium benzoate and basic hydrolysis of the benzoate ester (VI). The sulfoxide monomer (IX) was obtained from (VII) by protection with trimethylsilyl triflate yielding (VIII), and then oxidation with m-chloroperbenzoic acid to (IX). Coupling of monomers (VII) and (IX) using the sulfoxide glycosylation method in the presence of triflic anhydride produced a mixture of disaccharide (X), its desilylated analogue (XI), and trisaccharide (XII), which were separated by flash chromatography. Oxidation of disaccharide sulfide (X) with m-chloroperbenzoic acid provided sulfoxide (XIII). On the other hand, trisaccharide (XII) was desilylated with HF.Pyr to afford the corresponding alcohol (XIV).