Abstract
Previously unreported N,N′-ketal quinazolinone enantiomers [(−)-1 and (+)-1] and a new biogenetically related compound (2), along with six known compounds, 2-pyrovoylaminobenzamide (3), N-(2-hydroxypropanoyl)-2 amino benzoic acid amide (4), pseurotin A (5), niacinamide (6), citreohybridonol (7), citreohybridone C (8) were isolated from the ascidian-derived fungus Penicillium sp. 4829 in wheat solid-substrate medium culture. Their structures were elucidated by a combination of spectroscopic analyses (1D and 2D NMR and Electron Circular Dichroism data) and X-ray crystallography. The enantiomeric pair of 1 is the first example of naturally occurring N,N′-ketal quinazolinone possessing a unique tetracyclic system having 4-quinazolinone fused with tetrahydroisoquinoline moiety. The enantiomeric mixtures of 1 displayed an inhibitory effect on NO production in lipopolysaccharide-activated RAW264.7 cells, while the optically pure (–)-1 showed better inhibitory effect than (+)-1.
Highlights
Ascidians have continued to attract a widespread interest for a long time as an important resource for marine natural products with novel structures and potent pharmacological activities [1,2]
Subsequent chemical investigation led to the isolation of a pair of novel N,N′-ketal quinazolinone enantiomers, (±)quinazolinone enantiomers, (±)-penicamide
(±)-penicamide A is the first example of N,N′-ketal quinazolinone alkaloid that possesses a unique tetracyclic system 6/6/6/6 with 4-quinazolinone fusing with tetrahydroisoquinoline
Summary
Ascidians have continued to attract a widespread interest for a long time as an important resource for marine natural products with novel structures and potent pharmacological activities [1,2]. Novel antitumor antibiotics lomaiviticins A and B containing unique dimeric diazobenzofluorene glycoside structures were obtained from ascidian-associated actinomycetes. Our research group has focused on the secondary metabolites of ascidian-derived fungi isolated from the South China Sea in recent years [9,10]. 4829 was isolated from the ascidian Styela plicata, collected from the South. China Sea. Subsequent chemical investigation led to the isolation of a pair of novel N,N0 -ketal. 48292was of 10 isolated from the ascidian Styela plicata, collected from the South China Sea. Subsequent chemical investigation led to the isolation of a pair of novel N,N′-ketal quinazolinone enantiomers, (±)quinazolinone enantiomers,. 0 -ketal quinazolinone possessing a unique tetracyclic the first example of naturally occurring. N,N naturally occurring N,N′-ketal quinazolinone possessing a unique tetracyclic system having 4system having 4-quinazolinone fused with tetrahydroisoquinoline.
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