Collect. Czech. Chem. Commun. 1987, 52, 1325-1330

Synthesis of 5α-cinobufagin

Yoshiaki Kamanoa, Pavel Drašarb, George R. Pettita and Machiko Tozawac

a Cancer Research Institute and Department of Chemistry, Arizona State University, Tempe, Arizona 85287, U.S.A.
b Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6, Czechoslovakia
c Department of Chemistry, The Jikei University, School of Medicine, 8-3-1, Kokuryo, Chofu-shi, Tokyo, 182 Japan


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).