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Communication | Regular issue | Vol 14, No. 2, 1980, pp.163-168
Published online, 1st January, 1970
DOI: 10.3987/R-1980-02-0163
A New 2-Pyrone Synthesis and Its Application to Bufadienolide Synthesis

Yoshio Takeuchi, Yutaka Makino, Koichi Maruyama, and Eiichi Yoshii*

*Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, Toyama 930-0194, Japan


A synthetic method of 4-, 5-, and 6-alkyl-2-pyrones from an appropriately substituted α,β-unsaturated ketone or aldehyde was presented. The reaction sequence consisted of 1) conjugate addition of a methylthio- or phenylthioacetate to the enone by use of the corresponding thiomalonate, 2) acid-catalyzed enol lactonization of the adduct, and 3) oxidative elimination of the thio group. Application of this method to a 21-oxo-20-methylenepregnane leading to a new method for the synthesis of bufadienolides was also described.