The condensation of 1,3,4,6-tetra-O-acetyl-D-glucopyranose (I) with 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate (II) by means of BF3/Et2O in dichloromethane gives the disaccharide (III), which is treated with HBr/AcOH in dichloromethane to yield the active bromo derivative (IV). The glycosylation of diosgenin (V) with the disaccharide (IV) by means of CdCO3 in hot acetonitrile affords the protected diosgenyl disaccharide (VI), which is submitted to a selective deprotection of the acetyl groups by means of guanidine in methanol/dichloromethane to provide the key intermediate (VII). The benzylidenation of (VII) by means of benzaldehyde dimethylacetal and CSA in hot DMF gives the cyclic ketal (VIII), which is acetylated with Ac2O and pyridine to yield intermediate (IX). The hydrolysis of the benzylidene group of (IX) by means of hot AcOH yields the dihydroxy saccharide (X).

The selective silylation of the primary OH group of (X) by means of Tbdms-Cl and imidazole gives the silyl ether (XI), which is condensed with 2,3,4-tri-O-acetyl-alpha-L-rahmnopyranosyl trichloroacetimidate (XII) by means of BF3/Et2O in dichloromethane to provide the protected diosgenyl trisaccharide (XIII). The desilylation of (XIII) by means of TBAF in THF gives the intermediate (XIV), which is finally fully deacylated by means of MeONa in MeOH/dichloromethane to afford the target diosgenyl trisaccharide.