Biosynthetic origin of N-methyl-3-(3-furyl)-alanine in cyclic peptides produced by Stachylidium sp

Marine fungi are in the focus of research as a source of structurally novel compounds. The marine-derived fungus Stachylidium sp. was isolated from the sponge Callyspongia sp. cf. C. flammea, which was collected at Bare Island, Sydney, Australia. Culture on a biomalt medium supplemented with sea salt yielded an ethyl acetate extract which was chemically investigated and led to the isolation of four new N-methylated cyclic peptides.

Some of these peptides contain the amino acid N-methyl-3-(3-furyl)-alanine, which is a rare amino acid only reported once before in heptapeptides from the fungus Rhizopus microsporus [1]. The biosynthetic origin of this rare amino acid moiety was investigated using stable isotope feeding experiments. Isotopic enrichment and ¹³C-¹³C coupling constants observed for the N-methyl-3-(3-furyl)-alanine, after feeding of [U-¹³C] glycerol and [1-¹³C] glucose, suggested a shikimate origin for its biosynthesis.

Keywords: marine fungi, cyclic peptides, Stachylidium sp., N-methyl-3-(3-furyl)-alanine, biosynthesis

References:

[1] Steyn, P.S., et al., J.Chem.Soc.Chem.Commun.1983,47.