(+/-)-Pabmaragramin, A Scalemic Meroterpenoid Produced By Marasmius Graminum Via Precursor-Assisted Biosynthesis

A pair of novel scalemic meroterpenoid dimers, (+)- and (-)-pabmaragramin (1), featuring an unprecedented 6/6/5/6/6/6/5 seven-membered ring system, were obtained from Marasmius graminum via precursor-assisted biosynthesis (PAB). Their structures and absolute configurations were determined on the basis of extensive spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. A plausible biosynthetic pathway for 1 was proposed. Additionally, (+)-1 and (-)-1 exhibited inhibitory activity against alpha-glucosidase with IC50 values of 3.4 mu M and 12.0 mu M, respectively. (C) 2020 Elsevier Ltd. All rights reserved.