Premium
Bioactive Natural Products from the Endophytic Fungus Ascochyta sp. from Meliotus dentatus – Configurational Assignment by Solid‐State CD and TDDFT Calculations
Author(s) -
Krohn Karsten,
Kock Ines,
Elsässer Brigitta,
Flörke Ulrich,
Schulz Barbara,
Draeger Siegfried,
Pescitelli Gennaro,
Antus Sándor,
Kurtán Tibor
Publication year - 2007
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200600907
Subject(s) - time dependent density functional theory , chemistry , isocoumarin , absolute configuration , derivative (finance) , stereochemistry , computational chemistry , density functional theory , financial economics , economics
Two new metabolites, (4 S )‐(+)‐ascochin ( 1a ) and ( S , S )‐(+)‐ascodiketone ( 3 ), together with the known compounds (3 R ,4 R )‐(–)‐4‐hydroxymellein ( 2 ), ent ‐ α ‐cyperone ( 4 ) and (3 S ,4 R )‐(–)‐dihydroxy‐(6 S )‐undecyl‐α‐pyranone ( 5 ) were isolated from cultures of the of the endophytic fungus Ascochyta sp. The biologically active isocoumarin derivative, (4 S )‐(+)‐ascochin ( 1a ), has an unusual substitution pattern which was confirmed by X‐ray diffraction. Its absolute configuration was determined by our solid‐state TDDFT CD methodology using the X‐ray coordinates as input for the calculation. By catalytic hydrogenation, (4 S )‐(+)‐ascochin was converted into the corresponding (3 S ,4 S )‐dihydroisocoumarin derivative 1b . The measured and TDDFT calculated CD spectra enabled studies on the correlation between absolute configuration and n‐π* transition Cotton effect. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)