Structure determination of two extractives from Aspergillus amstelodami by nuclear magnetic resonance spectroscopy

Abstract

Spectral evidence supports the assignment of structures (1) and (2) to two substances extracted from the mycelium of Aspergillus amstelodami; they can be obtained by thermal condensation of auroglaucine with neoechinuline B and neoechinuline C, respectively, which are all known metabolites of the fungus.

Biologically Active Echinulin-Related Indolediketopiperazines from the Marine Sediment-Derived Fungus Aspergillus niveoglaucus

“…The HRESIMS spectrum of compound 1 suggested a molecular formula of C 43 H 49 N 3 O 5 (calcd for C 43 H 49 N 3 NaO 5 , 710.3564), which corresponds to 21 double-bond equivalents. An analysis of the 1 H and 13 C-NMR data together with the DEPT and HSQC data (Supplementary Data S1-S6) led to the identification of 1 as a known compound, cryptoechinuline B [15]. A direct comparison of the NMR data of 1 with literature data [15,16] confirmed the full identity of the planar structure of 1.…”

“…An analysis of the 1 H and 13 C-NMR data together with the DEPT and HSQC data (Supplementary Data S1-S6) led to the identification of 1 as a known compound, cryptoechinuline B [15]. A direct comparison of the NMR data of 1 with literature data [15,16] confirmed the full identity of the planar structure of 1. The optical rotation of 1 was near zero, indicating that 1 was a racemic mixture.…”

Metabolites from the marine fungus Eurotium repens

“…Another proton with HMBC correlations with C-2 (δ C 141.4), C-3 (δ C 104.1), C-8 (δ C 128.9), and C-9 (δ C 132.2) was located on a N atom in an indole ring. These data and the presence of a α,α-dimethylallyl group (δ H 1.51, 6H, δ C 27.8, 27.9; δ H 5.15, 2H, m, δ C 112.3; δ H 6.10, 1H, dd, δ C 145.7) and two isopentenyl substituents indicated that 4 belonged to the echinulin series of metabolites, which are characteristic of certain higher plants and fungi [14][15][16][17][18]. The mass spectrum, NMR spectra, and specific rotation were in excellent agreement with those of echinulin isolated from higher plants [14].…”

Dioxopiperazine Alkaloids Produced by the Marine Mangrove Derived Endophytic Fungus Eurotium rubrum

“…In addition, eight known dioxopiperazine derivatives, including variecolorin L (3) [8], echinulin (4) [9], isoechinulin A (5) [10], dihydroxyisoechinulin A (6) [4], preechinulin (7) [11], neoechinulin A (8) [12], neoechinulin E (9) [12], and cryptoechinuline D (10) [13], were also isolated and identified. It deserves to be mentioned that just at the time when we started to prepare this manuscript, compound 3 was reported as a new metabolite of Aspergillus variecolor B-17, a halotolerant fungal strain isolated from a sediment collection of a salt field in inner Mongolia, China [8].…”

“…This observation was supported by the fact that the aliphatic CH 2 and CH groups at d(C) 30.3 and 55.6 (for C (8) and C(9), resp.) in the 13 C-NMR spectrum of 3 were replaced by the olefinic CH group and quaternary C-atom at d(C) 114.9 (C(8)) and 128.1 (C(9)), respectively, in the (Table). Detailed examination of the NMR spectral data and comparison with those reported for echinulin (4, Table) [9] showed that the structures of these two compounds are very similar.…”