ISSN:
0749-1581
Keywords:
1H NMR
;
13C NMR
;
NOESY
;
INADEQUATE
;
lanthanide shift reagents
;
brown algae
;
sesquiterpenes
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
From the marine brown alga Dictyopteris delicatula Lamaouroux, two new (1, 3) and two previously reported sesquiterpenes (2, 4) were isolated and characterized. Compound 1 was identified as 4β,5α-dihydroxycubenol and 2 was found to be a non-racemic mixture of (±)-torreyol. Compound 3 was characterized as cubenol-3-one and 4 was identified as cubenol. For the assignment of the complete relative stereochemistry of compounds 1 and 2, it was necessary to employ extensive 2D NMR methodologies in combination with the lanthanide shift reagent europium(III) tris(1,1,1,2,2,3,3)-heptafluoro-7,7-dimethyl-d6-octane-4,6-dione-d3 [Eu(fod)3]. Anomalous proton shielding effects which occurred on addition of Eu(fod)3 to compound 1 suggested that classical lanthanide-induced shift (LIS) analysis for predicting proton chemical shifts was not applicable. Application of 2D NOESY measurements to NMR samples of 1 and 2 containing Eu(fod)3 clearly demonstrated an alternative to classical methods for interpreting lanthanide-induced shifts. The enhanced value of shift reagnents of this type as an aid to structure determination and as for assignment purposes is demonstrated.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260330305
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