Structure Elucidation of Lolitrem F, a Naturally Occurring Stereoisomer of the Tremorgenic Mycotoxin Lolitrem B, Isolated from <i>Lolium perenne</i> Infected with <i>Acremonium lolii</i>

Abstract

A new lolitrem, lolitrem F ( 2 ), was isolated from endophyte-infected perennial ryegrass. Its structure was shown by mass spectrometry and one- and two-dimensional NMR spectroscopy to be a 31,35- cis -fused isomer of lolitrem B. Base-catalyzed epimerization of 2 and lolitrem B ( 1 ) afforded their 31-epimers ( 4 and 3, respectively). Comparison with spectral data for 1 and 31- epi -lolitrem B ( 3 ) established lolitrem F to be 35 -epi -lolitrem B. Compounds 1, 2, and 4 were equally tremorgenic in a mouse bioassay, but 3 was nontremorgenic. Base-catalyzed exchange of H-31 was found to permit efficient incorporation of deuterium (and potentially, therefore, of tritium) into 1 and 3 . Keywords: Acremonium lolii; Lolium perenne; endophyte; lolitrem; tremor; ryegrass staggers; neurotoxin; mycotoxin