Glycals in the stereoselective synthesis of triterpene 2-deoxy-α-L-glycosides under conditions of acidic catalysis

3 beta-Hydroxy triterpenes of the oleanane, ursane, and lupane types were successfully glycosylated with acetylated L-glucal and L-rhamnal under conditions of acidic catalysis (anhydrous cation-exchange resin and LiBr). The 2-deoxy- and 2,6-dideoxy-alpha-L-carabino-hexopyranosides (1-5) were stereoselectively prepared in 83-90% yields, following deacetylation under mild conditions, which led to the target triterpene 2-deoxy-alpha-L-glycosides (6-10).