Compounds of the formula (I) for use as an estrogen receptor -β-selective ligand are described wherein: X is O or S; and R1, R3-R6 are as described in the specification. The use of these compounds in treating Alzheimer's disease, anxiety disorders, depressive disorders, osteoporosis, cardiovascular disease, rheumatoid arthritis and prostate cancer is described; as are processes for making them. 展开▼