In pursuit of pestalotiopsin A via zirconocene-mediated ring contraction

[graphics] An asymmetric route from the epimeric,- hydroxy esters 4 and 5 to the densely functionalized (+)-10 and (-)-10, respectively, is described. Either cyclobutanol can be made available as the predominant product. The levorotatory antipode has been transformed into the advanced intermediate 21 bearing side chains destined to become incorporated into the cyclononene ring of the title compound (1).