The natural timosaponin BII, (25S)-26-O-β-D-glucopyranosyl-22-hydroxy-5β-furostane-3β,26-diol-3-O-β-D-glucopyranosyl-(1→2)-β-D-galactopyranoside, isolated from the rhizomes of Anemarrhena asphodeloides Bunge (Liliaceae), has been efficiently synthesized in ten steps and 18% overall yield. The strategy of using a partially protected glycosyl donor was applied to facilitate target synthesis. The cytotoxic activities of structurally related compounds were evaluated against HL-60 human promyelocytic leukaemia cells.