Syntheses of three optically pure, deoxygenated myo-inositol 1,4,5-trisphosphate analogues from quebrachitol are reported together with their binding affinities and 45Ca2+ release activity. The ligand-binding affinities of the analogues were determined using membrane preparations from bovine adrenal cortex. The 45Ca2+ release activities were compared to that of Ins(1,4,5)P3, using the calcium mobilizing receptor of saponin permeabilized SH-SY5Y human neuroblastoma cells. 1d-3-deoxy-Ins(1,4,5)P3 (26) and 1d-2,3-dideoxy-Ins(1,4,5)P3 (22) exhibited very potent ligand and agonist properties, while 1d-2,3,6-trideoxy-Ins(1,4,5)P3 (19) was much less potent. These data provide solid evidence of the critical role which HO-6 of Ins(1,4,5)P3 plays in its binding affinity and its Ca2+ mobilizing activity.