Mortiamides A–D, Cyclic Heptapeptides from a Novel Mortierella sp. Obtained from Frobisher Bay

Four new cyclic heptapeptides, mortiamides A–D (1–4), were obtained from a novel Mortierella sp. isolate obtained from marine sediment collected from the intertidal zone of Frobisher Bay, Nunavut, Canada. The structures of the compounds were elucidated by NMR spectroscopy and tandem mass spectrometry. The absolute configurations of the amino acids were determined using Marfey’s method. Localization of l and d amino acids within each compound was ascertained by retention time comparison of the partial hydrosylate products of each compound to synthesized dipeptide standards using LC-HRMS. Compounds 1–4 did not exhibit any significant antimicrobial or cytotoxic activity.