4,5-Epoxy-17B-hydroxy-5-androstan-3-one is used in the preparation of steroidal carbonitriles as potential aromatase inhibitors. 4a,5-Epoxy-17B-hydroxy-5a-androstan-3-one inhibits HIV-1 nuclear regulatory protein tat.Solubility:Dichloromethane, Ethyl Acetate, Toluene