Design, synthesis, and testing of potential antisickling agents. 7. Ethacrynic acid analogues

In search of a drug to treat sickle cell anemia, several analogues of the diuretic ethacrynic acid (ECA) have been synthesized and found equivalent in antigelling potency to ECA, but they have moderate or little diuretic activity. Structure-activity studies revealed that most of the highly active derivatives contain an acryloyl moiety. The latter functionality reacts covalently with protein sulfhydryl groups via a Michael addition reaction. Other derivatives, which lack the acryloyl moiety, showed notably lower antigelling activity. Since the antigelling assay is run under anaerobic conditions, activity implies a stereochemical inhibition of polymerization of deoxyhemoglobin S. The solubility ratios obtained from [HbS drug]/[HbS control] of several compounds (Table I) are near those expected for a drug with clinical potential (1.06-1.20 at tolerable doses in vivo).