New tetramic acid derivatives from the deep-sea-derived fungus Cladosporium sp. SCSIO z0025

Abstract

Eight new tetramic acid derivatives, cladosporiumins A–H (1–8) were isolated from a culture broth of Cladosporium sp. SCSIO z0025 derived from the deep-sea sediment collected from Okinawa Trough. Their structures were elucidated by extensive spectroscopic data analysis. Compounds 1–3 were unique 3-acyltetramic acids with a hexyl enic alcohol side chain and a six-membered lactone ring substituted at C-3 of the 2, 4-pyrrolidinedione skeleton. The absolute configurations of chiral carbons of the 2, 4-pyrrolidinedione unit in 1–4 and 7 were established by quantum chemical calculations of the electronic circular dichroism (ECD) spectra. And the absolute configurations of chiral carbons of the six-membered lactone ring in 1–3 were established by density functional theory calculation of their 13C NMR chemical shifts. In addition, all the compounds were tested for cytotoxic, antibacterial, anti-biofilm, and AchE inhibitory activities.