Synthesis of some cyclopropyl-γ-lactones as analogues of cytotoxic α-methylene-γ-lactones

Abstract

Five novel α-cyclopropyl-γ-lactones [(5), (8), (12), (18), and (19)] have been prepared. The spirocyclopropyl lactones (5), (8), and (12) were prepared by addition of a keten to an alkene followed by a series of reactions involving reduction, 1,4-dehydrohalogenation, and Baeyer–Villiger oxidation. The optimum order for the last three steps depends upon the structure of the final product. The 2-oxatricyclo[3.3.0.0^4,6]octanones (18) and (19) were prepared in high yield from the corresponding 2-bromobicycloheptanone by Baeyer–Villiger oxidation and dehydrobromination.