Talarolide A, a Cyclic Heptapeptide Hydroxamate from an Australian Marine Tunicate-Associated Fungus, Talaromyces sp (CMB-TU011)

A miniaturized 24-well plate microbioreactor approach was used to explore secondary metabolite media dependence in an Australian marine tunicate-associated fungus, Talaromyces sp. (CMB TU011). Detailed chemical investigations of an antifungal M1-saline cultivation yielded talarolide A (1), only the second reported natural cyclic peptide hydroxamate, and the first from a fungus. The antifungal properties of the M1-saline extract were attributed to the known diterpene glycoside sordarin (2). Structure elucidation of 1 and 2 was achieved by detailed spectroscopic analysis, with amino acid configurations in 1 assigned by the C-3 and C-18 Marfey's methods, and L-Ala and D-Ala regiochemistry by the recently reported 2D C-3 Marfey's method.