Metabolic Products of the Endophytic Fungus Microsphaeropsis sp. from Larix decidua

Five new metabolites, palmarumycin M 1 ( 1a ) and M 2 ( 3 ), papyracillic acid C ( 6 ) and the microsphaeropsins A ( 7 ) and B ( 8 ) were isolated from the fungus Microsphaeropsis sp. together with the known decaspirone ( 2 ) and the papyracillic acids A and B ( 4 and 5 ). Their structures were determined by means of spectroscopic data including HREIMS, 1 H NMR, 13 C NMR, 2D NMR (HMQC, HMBC, NOESY) and X‐ray single crystal analysis. The absolute configuration of palmarumycin M 1 ( 1a ) was determined by single‐crystal X‐ray analysis of the bis(4‐bromobenzoate) 1c and the relationship between 1a , 2 and 3 established by chemical transformation of 1a into 2 and of 3 into 2 . The relative configuration of papyracillic acids A–C ( 4 – 6 ) was revised and their absolute configuration determined by comparison of TDDFT‐calculated and experimental solid‐state CD spectra.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)