A new alkaloid, named aurechinulin, was isolated from ether extract of freeze-dried mycelium of Aspergillus amstelodami IFO-6667. Elemental analysis and high-resolution mass spectral data showed the molecular formula of aurechinulin to be C
43H
49O
5N
3. This formula is equal to the sum of the molecular formulae of auroglaucin (2), C
19H
22O
3, and cryptoehinulin A (3), C
24H
27O
2N
3, both of which are metabolites of Aspergillus amstelodami. Alkaline hydrolysis of aurechinulin afforded 2-(1, 1-dimethylallyl)-6-(3, 3-dimethylallyl)-3-indolecarbaldehyde (4), an alkaline hydrolysis product of cryptoechinulin A (3). Analysis of proton magnetic resonance and carbon magnetic resonance (CMR) indicated the structure 1a for aurechinulin. Aurechinulin (1a) was synthesized by the Diels-Alder reaction of auroglaucin (2) and cryptoechinulin A (3) in 37% yield. A by-product (regio-or stereoisomer of 1a) was isolated in this Diels-Alder reaction in about 8% yield. Stereochemistry of 1a, except for C-3e, was determined as indicated in the structure of 1a.
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