Mechanism of formation of natural cyclopropanes: synthesis of postulated intermediates in presqualene and chrysanthemyl alcohol biosynthesis

Abstract

The α-unsaturated esters (15), (28), and (33) have been used in deconjugative additions to ketones, to provide the β,γ-hydroxy esters (17), (18), (29), (30), and (37) and hence the unsaturated diols (22), (23), and (38). These diols have been postulated as precursors to the natural cyclopropanes chrysanthemyl alcohol and presqualene, through homoallylic participation. Experiments with cell-free extract of Artemisia annua foliage show that neither diol (22) nor (23) is converted to chrysanthemyl alcohol. Limited experiments with an homogenate of Rhizopus arrhizus provide little support for the intervention of the diol (38) in squalene biosynthesis.