Stereoselective introduction of a carboxy group into a santonin derivative for higher terpene lactone synthesis

Abstract

While conjugate addition of potassium cyanide or diethylaluminium cyanide to the enone (5) yielded the β-cyano addition product (6), reaction of the same substrate with a vinyl Grignard reagent in the presence of copper(I) iodide gave rise to formation of the stereochemically reversed addition product (10). The products were transformed to the carboxylic acid (8a) and the epimeric acid (13a), respectively.