PREGNANE AND 21-NORPREGNANE DERIVATIVES OF OUABAIN THAT BIND TO THE DIGITALIS RECEPTOR

14 beta-Hydroxy-5 beta-pregnane and 14 beta-hydroxy-21-nor-5 beta-preg nane derivatives of ouabain were synthesised and their structures esta blished by NMR measurements. Binding affinity in an [H-3]ouabain radio ligand binding assay was determined. Pregnane derivatives of ouabain a re more polar than pregnane rhamnoside derivatives of digitoxigenin. W hereas ouabain binds similarly to digitoxigenin rhamnoside, the pregna ne derivatives of ouabain have significantly weaker binding affinity t han their congeners from digitoxigenin.