Methylation of E, catalyzed by rhodium, produced F . The dehydroxylation and selective oxidation of the secondary hydroxy group of F produced G . G reacted with triphenyl phosphoranylidene ketene and the ester bonds in G were hydrolyzed to produce ouabagenin, a precursor to ouabain.
42.
Its fragrant flowers feature a white corolla, topped by red or purple colour, with pink corona lobes . " S . gratus " has been used medicinally : ouabain derived from the plant's seeds is used as a treatment for heart failure.
43.
However, digitoxin, digoxin and several other cardiac glycosides, such as ouabain, are known to have steep dose-response curves, i . e ., minute increases in the dosage of these drugs can make the difference between an ineffective dose and a fatal one.
