HETEROCYCLES

Heterocycles has a pay-per-view service for Non-subscribers.
You will be able to directly purchase the full text article through PayPal.
Your purchased Paper can be downloaded after the payment is completed.
An e-mail will be sent the URL to download the paper.
If you have any questions, please contact: purchase@heterocycles.com

Price: ¥ 4,400 (Yen only)
Period: This Article can be accessed for 7 days.

■ 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

Abstract

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.