Inhibitors of myo-Inositol Monophosphatase, ATCC 20928 Factors A and C Isolation, Physico-chemical Characterization and Biological Properties

During the course of a screening program for inhibitors of myo-inositol monophosphatase we fermented the strain ATCC 20928, a known producer of L-671, 776. We now show that this strain produces a complex of at least three sesquiterpenic compounds, L-671, 776 (termed factor B) and two structurally related substances, termed factors A and C. Both factors A and C, like L-671, 776, exhibited inhibitory activity against myo-inositol monophosphatase. Six other fungi producing the above mentioned compounds were also isolated and taxonomically characterized.