Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. I. α,β‐ und β,γ‐ungesättigte Lactonring‐methylierte Cardenolide

Abstract

Partial Syntheses of Cardenolides and Cardenolide Analogues. I. α,β‐ and β,γ‐Unsaturated Lactone Ring‐Methylated Cardenolides Base‐catalyzed methylation of digitoxigenin 1a with methyl iodide and sodium hydride in DMF leads to the α,β‐unsaturated cardenolides 2–5 and, after rearrangement of the CC‐double bond, to the β,γ‐unsaturated cardenolides 6 and 7 . Opening of the lactone ring results in the formation of 8 . Allylic oxidation of 4b affords the 14,21‐epoxide 10 . Only the 22‐methyl derivative 4a and its 3‐O‐tridigitoxoside 4d show strong biological effectivity, whereas methylation at 21R‐ or 21S‐position results in considerable loss in activity.