Eldecalcitol (CAS 104121-92-8) is a synthetic analog of 1α,25-dihydroxyvitamin D3, a potent active form of vitamin D. Chemically, it is (1S,2S,5Z,7E,22E)-9,10-Secocholesta-5,7,10(19),22-tetraene-1,3-diol with a specific side chain modification for enhanced stability and activity. As a specialty chemical, it is used in pharmaceutical research and development for osteoporosis treatments. It regulates calcium and phosphate metabolism, increases bone mineral density, and reduces fracture risk in postmenopausal women and elderly patients. Additionally, it manages secondary hyperparathyroidism in chronic kidney disease by suppressing parathyroid hormone levels, aiding bone health.