Fig. 2.
Formation of methylpiperazine (MPPZ) derivative of phenolic estrogens; showing an example of derivatization of 17β-estradiol with 1-(5-fluoro-2,4-dinitrophenyl)-4-methylpiperazine (PPZ) in the presence of sodium bicarbonate (NaHCO3) followed by reaction with methyl iodide (CH3I) to create the charged moiety.