Synthesis and crystal structures of a 3-acetylated (20S,24S)-ocotillol-type saponin and its C-24 epimer.

In order to study the in vivo protective effect on myocardial ischemia, (20S,24R)-epoxydammarane-12β,25-diol, (V), and (20S,24S)-epoxydammarane-12β,25-diol, (VI), were synthesized through a novel synthetic route. Two key intermediates, namely (20S,24R)-3-acetyl-20,24-epoxydammarane-3β,12β,25-triol, (III) [obtained as the hemihydrate, CHO·0.5HO, (IIIa), and the ethanol hemisolvate, CHO·0.

Synthesis and crystal structures of C24-epimeric 20(R)-ocotillol-type saponins.

Ocotillol-type saponins have a wide spectrum of biological activities. Previous studies indicated that the configuration at the C24 position may be responsible for their stereoselectivity in pharmacological action and pharmacokinetics. Natural ocotillol-type saponins share a 20(S)-form but it has been found that the 20(R)-stereoisomers have different pharmacological effects.