Enantioselective enzymatic sterol synthesis by ultrasonically stimulated bakers' yeast

We now wish to report that an "ultrasonically stimulated" suspension of bakers' yeast (Saccharomyces cerevisiae ) is an inexpensive, convenient, and direct source of a sterol cyclase which can be employed for the gram-scale enzymatic cyclization of squalene oxide and squalene-like substrates. Additionally, the enzymatic method is completely enantioselective as exemplified by a synthesis of lanosterol (2) and the cytotoxic agent, ganoderic acid Z (4a).