Premium
New Antifungal `Quinone Methide' Diterpenes from Bobgunnia madagascariensis and Study of Their Interconversion by LC/NMR
Author(s) -
Schaller Frédéric,
Wolfender JeanLuc,
Hostettmann Kurt,
Mavi Steven
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010131)84:1<222::aid-hlca222>3.0.co;2-r
Subject(s) - chemistry , quinone methide , diastereomer , stereochemistry , proton nmr , bark (sound) , quinone , two dimensional nuclear magnetic resonance spectroscopy , carbon 13 nmr , diterpene , yeast , antifungal , biochemistry , microbiology and biotechnology , physics , acoustics , biology
Abstract Two new `quinone methide' diterpenes with a cassane skeleton were isolated from the root bark of Bobgunnia madagascariensis ( Desv. ) J. H. Kirkbr. & Wiersema (Leguminosae). The two compounds occurred as a diastereoisomer mixture 1 / 2 . Their structure was established as (4 R ,6a S ,10a S )‐ and (4 S ,6a S ,10a S )‐ 1,4,6a,7,8,9,10,10a‐octahydro‐4,11‐dihydroxy‐7,7,10a‐trimethyl‐2 H ‐phenanthro[1,2‐ c ]pyran‐6,12‐dione by spectroscopic methods and by comparison with the data obtained for another `quinone methide' diterpene isolated previously from the same plant and identified by single‐crystal X‐ray analysis. 1 H‐ and 13 C‐NMR signals were assigned by extensive in‐mixture 2D correlation experiments, and 1 H‐NMR spectra of the separated diastereoisomers 1 and 2 were recorded by on‐flow LC/NMR. The interconversion of 1 and 2 was followed by repeated stop‐flow LC/NMR experiments over a two‐hour period. Compounds 1 and 2 showed moderate antifungal properties towards human pathogenic fungi, in particular the yeast Candida albicans.