Abstract: Novel tetrasubstituted pyrazole derivatives bearing a nitro substituent on their A- phenol ring were synthesized and their binding affinity towards the estrogen receptor (ER) subtypes ERα and ERβ was determined. Among compounds tested, the 2-nitrophenol derivative 5c was found to bind satisfactorily to both estrogen receptor subtypes (RBAα= 5.17 and RBAβ= 3.27). In general, the introduction of a nitro group into the A ring of these ...