Abstract
As part of research to search for antitumor agents in fungi originating from marine organisms, cephalimysins E–L were isolated from a culture broth of Aspergillus fumigatus that was separated from the marine fish Mugil cephalus. One- and two-dimensional nuclear magnetic resonance spectra revealed their planar structures, which are diastereomers of each other. Their absolute stereostructures were established by epimerization at C-8 with acidic methanol, nuclear Overhauser effect spectroscopy (NOESY), and circular dichroism (CD) spectroscopy. These demonstrated the detailed relationships between absolute configuration and CD Cotton effects. Additionally, in the growth inhibition assay against P388, HL-60, L1210, and KB cell lines, some of the fungal metabolites or reaction products exhibited moderate activities.
Highlights
Our group searched for active antitumor compounds in microorganisms in marine environments [1,2,3,4].We previously reported the isolation and structure determination of FD-838 and its three diastereomers, referred to as cephalimysins B–D, from a culture broth of the fungal strain A. fumigatus OUPS-T106B-5, which lives on the stomach wall of a marine fish, M. cephalus [5]
During a further search for novel active antitumor compounds from this fungal strain, we isolated eight new spiroheterocyclic-lactams designated as cephalimysins E–L (1–8), and their treatment with acidic methanol gave a set of eight unnatural forms (10 –80 ) to afford sixteen stereoisomers
We established the detailed relationships between absolute configuration and circular dichroism (CD) Cotton effects for new natural products, cephalimysins E–L (1–8), isolated a fungal strain separated from a marine fish together with unnatural products 10 –80
Summary
Our group searched for active antitumor compounds in microorganisms in marine environments [1,2,3,4]. FD-838 and cephalimysins B–D isolated from this fungal strain, had the S absolute configuration at the methoxy acetal carbon in common. During a further search for novel active antitumor compounds from this fungal strain, we isolated eight new spiroheterocyclic-lactams designated as cephalimysins E–L (1–8), and their treatment with acidic methanol gave a set of eight unnatural forms (10 –80 ) to afford sixteen stereoisomers. Drugs 2018, 16, x FOR PEER REVIEW orbital calculations This examination showed that compounds 1–8 were more stably produced from the plausible precursor with an E-olefin side chain thanshowed one with. Cotton effect as well as the elucidation of the relative configurations by Overhauser effect spectroscopy (NOESY) experiments
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