Cardenolide analogues. 3. A fast thin layer chromatographic separation of cardenolide diastereomers

Cardenolide diasteromeric mixtures may be analytically separated on 2.5 x 6.5 cm x 0.25 mm pre-coated silical gel 60 F-250 (EM) tlc plates (cut from 20 x 20 cm plates). Three successive developments in mixtures of CH2Cl2-EtOAc-MeOH achieve complete separation of diastereomers in less than 15 minutes, and 2--6 micrograms of sample is sufficient. This procedure facilitated the separation of several diastereomeric mixtures, including 20(R) and 20(S)-20,22-dihydrocardenolides. A single development produces separations sufficient for separating starting materials and products of common cardenolide types of reactions.