Antifungal Cyclic Peptides Dinemasporins from the Culture of Dinemasporium parastrigosum KT4144

Cyclic nonapeptides dinemasporins A1 (1),
A2 (2), A3 (3), B1 (4), and
B2 (5) were isolated from the solid culture of Dinemasporium parastrigosum KT4144. Structures were
assigned based on the first elucidation of compound 1 by analysis of spectroscopic data. Dinemasporins A2 (2) and A3 (3) feature a pyridinium cation derived from
the δ-amino group of an ornithine residue. The substitution
pattern of the aromatic ring moiety in 2 was established
by density-functional-theory (DFT)-based 13C NMR chemical
shift calculations and corroborated by the identification of the structurally
related dinemaxanthone C (6), obtained from the same
culture. Dinemasporins B1 (4) and B2 (5)
possess a secondary hydroxy group at C-θ of the 2-aminodecanoic
acid (ADA) residues in 1 and 2, respectively.
Extended Mosher analysis of 7, obtained by acidic hydrolysis
of 4 followed by protection of the amino acid moiety
in the hydrolysate, revealed that 4 is a diastereomeric
pair at C-θ of the ADA residue. Although 1 exhibited
potent antifungal activity against rice brown spot fungus Bipolaris oryzae, at 1.0 μg/mL, the other peptides
isolated showed very low or no fungal growth inhibition.