Preparation of several ring A-modified cardenolides from digitoxigenin is presented. 3, 5-Seco-4-nor-cardenolides were prepared by oxidative cleavage of the ring A of the 3-oxo-Δ4-derivative with ruthenium tetroxide and 4-oxa-cardenolides were derived from the 3, 5-seco-4-nor-cardenolide. The structure-activity relationship in these ring A-modified cardenolides is discussed.
