Bone targeted drugs: 2. Synthesis of estrogens with hydroxyapatite affinity

Abstract The utility of the bone targeting 4-carboxy-3-hydroxy-1,2-pyrazole heterocycle was tested by the synthesis of hybrids with the non-steroidal estrogen hexestrol. Compounds 1 and 2 demonstrated significant hydroxyapatite affinity, while maintaining weak estrogenic activity in whole cell assays.