A stereoselective synthesis of digitoxin. On cardioactive steroids. XIII

The first highly stereoselective synthesis of digitoxin is described. The furyl derivative of digitoxigenin was coupled with one unit of digitoxose using our previously described acid catalyzed method. For the second and third glycosylation a new method involving ethyl thioglycosides and 1,3-participation by a p-methoxy benzoate group was developed. As the final step after deprotection of the triglycoside, the 17-furyl group in the steroid aglycone was converted to a butenolide by our oxidative method.