Unusual immunosuppressive pyridine-containing, bisnor- (c23), tetranor- (c21) and pentanor- (c20) sesterterpenoids from Tibetan Leucosceptrum canum

Six unusual pyridine-containing bisnor - (C 23 ), tetranor - (C 21 ) and pentanor - (C 20 ) sesterterpenoids were obtained from the medicinal plant Leucosceptrum canum of Tibetan origin. The immunosuppressive activities of these sesterterpenoids were observed.