Vitamin D3 (3B,5Z,7E)9, 10-Seco-cholesta-5, 7,10(19 )-trien-3B-ol There is a conjugated triene system in the structure in which there are a hydroxy group at C-3 on A ring, a methenyl group at C-10Vitamin D3 • (3β,5Z,7E)-9,10-Seco-cholesta-5,7,10(19)-trien-3β- ol • There is a conjugated triene system in the structure in which there are a hydroxy group at C-3 on A ring, a methenyl group at C-10. HO H