Three Novel, Structurally Unique Spirocyclic Alkaloids from the Halotolerant B-17 Fungal Strain of Aspergillus variecolor

摘要

During our search for novel antitumor lead compounds from microorganisms living under extreme conditions, three novel alkaloids, variecolortides A-C (1-3), were isolated from the mycelia of the halotolerant fungal strain Aspergillus variecolor B-17. The new compounds were found to share an unprecedented spiro-anthronopyranoid diketopiperazine structure, with a stable hemiaminal function, as corroborated by in-depth NMR-spectroscopic and mass-spectrometric analyses, as well as by a single-crystal X-ray analysis of 1. All compounds were shown to exhibit weak cytotoxic and antioxidant activities.