It has been suggested that the psi factors may function in a" hormonal" role in regulating the sporulation cycle of A. nidulans, an organism used extensively in biochemical and genetic research. 2 We report here an enantioselective synthesis of psiAB using asymmetric Alpine- borane and microbiological reductions as the key steps. Our synthetic strategy, which is outlined in Scheme I, was based on the recent employment of bakers' yeast ( ...