Probing the stereoselectivity of OleD-catalyzed glycosylation of cardiotonic steroids?
The glycosyltransferase OleD variant as a catalyst for the glycosylation of four pairs of epimers of cardiotonic steroids (CTS) are assessed. The results of this study demonstrated that the OleD-catalyze glycosylation of CTS is significantly influenced by
Cinobufagin (I) and cinobufotalin (IV) isolated from the Chinese toad venom preparation Ch'an Su were used as starting points for synthesis of 5α-cinobufagin (III) via the 3-oxo-4-ene derivative VII.Lithium borohydride reduction of ketone VII afforded 5α-cinobufagin (III) accompanied by 3-epicinobufagin (IX).Ring A diene II, was obtained as one of the dichlorodicyanobenzoquinone oxidation products of 3-oxocinobufagin (V).
Kamano, Yoshiaki,Drasar, Pavel,Pettit, George R.,Tozawa, Machiko