Massarilactones E‐G, new metabolites from the endophytic fungus Coniothyrium sp., associated with the plant Artimisia maritima

Abstract

Three new massarilactones E-G (1-3) and the massarilactone acetonide (4) were isolated from the ethyl acetate extract of the endophytic fungus Coniothyrium sp., associated with the plant Artimisia maritima. Their structures were determined by analysis of the 1D and 2D NMR and mass spectroscopic data. The structure of massarilactones E (1) was confirmed by X-ray diffraction analysis, and its absolute configuration determined by the solid-state CD/TDDFT method.

Circular dichroism of diglycosyl dichalcogenides in solution and solid state

“…Since its absolute configuration is known, the main purpose here is to test our solid-state TDDFT CD approach [25][26][27][28] on a compound containing the diselenide moiety, to which applications of TDDFT calculations are scarce (TDDFT calculations on selenium-containing compounds: refs 37, 38).…”

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

“…2-5 in Figure 6, a) with rotational strengths of alternating signs involving the four highest occupied and the two lowest virtual orbitals (both with negative eigenvalues [25] ), mostly confined to the enone and the alkene chromophores. Similar to an analogous case involving a compound with a compact polycyclic structure, [20] we re-optimized all bond lengths found in the solid-state geometry to explore the impact of possible libration effects introducing unnatural bond shortening in the X-ray structure. [26] This correction was in fact beneficial for obtaining a better agreement between experimental and computed spectra, but not decisive for assigning the absolute configuration; the CD spectrum computed on the original X-ray structure still showed the same trend as in Figure 6 (a), only with a weaker short-wavelength negative band.…”

Assignment of the absolute configuration of zwitterionic and neutral macropodumines by means of TDDFT CD calculations

“…On the contrary, the expected agreement between calculated and experimental CD spectra (in solution vs. solid state) will vary from case to case and cannot be generalized. However, the present report and all other examples so far examined [35][36][37][38][39][40][41][42] demonstrate that the solid-state CD/ TDDFT approach usually leads to very good agreements and allows firm configurational assignments.…”

“…A good agreement is thus expected between calculated and experimental spectra, as it was in fact observed in several published examples. [35][36][37][38][39][40][41][42] Therefore, macropodumines B and C offered us chances for: (a) a direct comparison of the solid-state and solution-based approaches on two similar compounds; and (b) running TDDFT CD calculations on a zwitterion, which-to the best of our knowledge-is unprecedented in the literature except for some applications on amino acids. 57 TDDFT calculations were executed employing the B3LYP and BH&HLYP hybrid functionals with TZVP and ADZP basis sets (see text for references).…”

“…The solid-state CD/TDDFT approach, recently developed by some of us, [35][36][37][38][39][40][41][42] made it possible to elucidate the absolute configuration of 1 on the basis of the X-ray experiment on its single crystal. The method is founded on the comparison between CD spectra measured in the solid state and those calculated 43,44 at TDDFT level of theory 45,46 on the X-ray structure.…”